You can grow these tasty nuts in your own backyard, if you have room and patience. The delicious flavor of pistachios doesn’t come cheap. They are not inexpensive and they require effort to pry from their shells. That being said, pistachios have a protein-rich flavor that begs us to eat just one more, and another, and another. What are pistachios?
The meat of a pistachio (Pistacia vera L.) is not technically a nut. Like apricots, olives, cherries, coconuts, and mangoes, pistachios are drupes, or stone fruits. Pistachios are the edible seeds held within a hard shell. When these seeds ripen, the shell pops open with an audible pop. In the world of botany, the thing that makes a drupe a drupe is that the fruit develops from a single ovary. How do pistachios grow? Pistachio trees need long, hot, dry summers and gentle winters to produce those hard-shelled nuts. Pistachio trees can tolerate a lot of salinity as long as they get hot, dry summers. Soggy soil will kill your pistachio tree, so good drainage is critical. Pistachios are a slow-growing, alternate bearing, deciduous tree that needs 600 to 1500 chill hours, depending on variety, to produce fruit. Those chill hours can be hard to come by in many warmer regions, but the trees are lovely and some varieties can be very productive. A healthy, mature pistachio tree can produce 110 pounds of seeds every other year. That’s a lot of pistachios! Pistachio varieties The following cultivars have been shown to produce well in the warmer regions:
Pistachio pollination Pistachio trees are dioecious. That means there are both male and female trees. You only need one male for up to 10 females for successful pollination, but these trees get rather large, so you probably won’t have room for more than one of each. Mature trees can reach 33 feet in height and should be spaced 20 feet apart. How to grow pistachios Plant pistachio rootstock from January through early May. Be sure to provide support by inserting a large, heavy stake next to the root ball. You will want the wind to push the tree toward the support for the best development. Irrigate the root ball immediately and follow with regular waterings until the root system is established. This may take several months, so be patient. Your pistachio tree will also need to be fertilized regularly. During the first dormant season, cut the top of the main shoot off, just above leaf buds. This heading cut will promote a solid structure later on. Pistachio pests and diseases A disease called panicle and shoot blight, caused by the Botryosphaeria fungi, kills flowers and young shoots of pistachio trees. In 2011, 50% of the Australia pistachio harvest was lost to anthracnose. Verticillium wilt can also be a problem. Severe drought has also reduced commercial production in many areas. Common pistachio pests include leaf-footed bugs, mealybugs, nematodes, and late season navel orangeworms. Harvesting pistachios After waiting for 5 to 7 years, you will finally be able to harvest your very own pistachios. Like almonds, this is done by shaking the tree. Ripe nuts fall and are collected from the ground. If you see any nuts with mold, toss them in the trash. That particular mold is carcinogenic. Also, be sure to dry your pistachios out completely before storing - they have been known to spontaneously combust. Don’t let all those problems discourage you or scare you off. These beautiful trees can produce an edible crop for decades, if cared for properly.
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Tiny brown spots on your apples? It might be bitter pit. Bitter pit is a disorder of apples. It is related to low calcium levels. Also known as blotchy cork and Baldwin spot, this disease can also affect quince and pears. Causes of bitter pit Much like blossom end rot, bitter pit occurs when there is not enough calcium in a fruit. Calcium deficiencies are almost unheard of west of the Rocky Mountains. Insufficient or irregular watering can make it hard for plants to move calcium to where they need it. Calcium is a low-mobility nutrient. It takes a lot of water to move calcium around once absorbed. Inadequate irrigation means newer leaves may look burnt or die due to a lack of calcium, regardless of how much is in the soil. The optimal range is 1000 to 1500 ppm.
How to control bitter pit
Many commercial growers spray trees with calcium, while others dip fruit in a calcium solution, but these methods are unrealistic for the home grower. Regular irrigation is the best way to avoid bitter pit in your apple crop. Applying too much fertilizer, thinning fruit too early, and thinning too much can increase the odds of bitter pit. Removing excessive vegetation without over-pruning can help reduce the likelihood of bitter pit. Maybe removing some foliage means more calcium for the rest of the tree. That's my guess, anyway. Bottom line: those spongy little dead spots won’t hurt you. But they create points of entry for pests and diseases that create more work for you later. You know, one of those ounce-of-prevention situations. Keep your trees healthy and treat them right to make your job easier. Cling peaches. Freestone fruit. What do those words mean? If you have ever bit into a sweet, juicy peach or nectarine, you may have discovered that the fruit practically fell away from the pit as you neared the center. Or, you may have had to fight for every morsel, leaving behind a ragged, fruit-covered pit. When the fruit comes away from the pit easily, it is called freestone. When the fruit clings to the pit, it is, you guessed it, a cling variety. Texture differences Freestone fruits tend to be more firm than clingstones. This makes them better suited for canning. The clingstone varieties are best for fresh eating, though you can certainly can them, or turn them into a delicious jam or chutney! Harvest times Clingstones are generally harvested May through August, while freestone varieties are harvested May through October. If you are going to plant a peach or nectarine tree, take the time to decide which type you want before you plant. Of course, biting into a fresh, sweet peach or nectarine, you won’t care if it’s a freestone or a cling!
Chickens, jays, and mockingbirds can wreak havoc on your fruit and nut tree crops unless you provide protection. Floating eye balloons, hanging old CDs, motion-sensing sprinklers, and noise cannons are just a few of the countless methods ‘guaranteed’ to protect your fruit and nut crop from marauding birds, but most of them do not work; not for long, anyway. Caging your tree is the only way to be sure that you get the lion’s share of your fruit or nut crop. The netting used over your tree cage will still allow pollinators easy access. Unfortunately, it also allows codling moths and other flying insect pests to reach your fruit and nut trees. Even so, birds and squirrels can take a big bite out of apple, apricot, almond, nectarine, fig, and other crops. Tree cages can stop that damage before it even starts. Plus, these cages stay up, year round, so there's no wrestling with netting every spring and fall. Store bought vs. DIY tree cages Store bought tree cages can be astronomically expensive and most of the really nice ones are in the UK. The added shipping costs make it impossible or unrealistic for most of us. Luckily, it is surprisingly easy to make a tree cage yourself for less than $50. If you can scrounge old tree supports, it’s even cheaper. Make your own tree cage This tree cage design is intended for dwarf variety trees that will be pruned to 6 to 8 feet tall and 8 feet wide. You can adjust the measurements for bigger trees, but longer lodge poles can be harder to find and more expensive.
3. Place one lodge pole in each hole and gently press the dirt you dug up back into the hole, making sure that the drilled hole runs outside to inside of the tree space, rather than side-to-side. You’ll see why in a minute. Also, dig one more hole to create the doorway space. 4. Take both 1”x2” boards and cut a 1/2-inch notch out of the middle of each, only cutting halfway through. I used a handsaw to make the perpendicular cuts and then a hammer and chisel to knock out the chad. Fit the 1”x2”s together in the middle and hammer together into a giant X-shape.
8. Drape bird netting over the X-shape and staple it down to make it taut. Ideally, you want birds and bats to bounce off, not get tangled. Bring the netting down over the sides until it reaches the chicken wire. You can use the wrapping wire from the roll of chicken wire (or string) to “sew” the netting to the chicken wire. I used heavy duty black thread and an embroidery needle.6. Staple 2’ chicken wire to the lodge poles, all the way around.
7. If you are really handy (which I am not), you can build yourself a fancy door. I opted for something far more simple: I cut a piece of bird netting that was larger than the door opening, attached it to the opening at the top, and ran a piece of thin scrap wood through the holes at the bottom. The wood weighs the netting down enough to keep chickens, mockingbirds, and jays away from my fruit and nut trees, and it’s easy to use. For added stability, you can add a cross piece above head height between one of the four lodge poles and the door lodge pole. Pineapple guavas are neither pineapples nor guavas, but they can make a good addition to your foodscape. Distant cousin to guavas, pineapple guava (Acca sellowiana, or Feijoa (fay-zho-uh) sellowiana) is a member of the myrtle family. Native to Brazil and Argentina, it is well suited to the Bay Area’s hot summers and cool winters. It is somewhat frost tolerant. The edible flowers look like tiny versions of bottlebrush and have a cinnamon flavor. (Of course, if you eat all the flowers, you won’t get any fruit!) Growth habits Pineapple guava is a relatively slow-growing perennial evergreen shrub that can eventually reach a height and width of 10 to 15 feet. Leaves are green on top and silvery underneath, which looks really nice when a breeze comes through. Pineapple guava plants grow best in USDA Hardiness zones 8 through 11 and they need 50 chill hours each winter to set fruit (I get 300 in the Bay Area). If temperatures are above 90 °F for too long, fruit set can be reduced. Pineapple guava are very drought tolerant, but they do need to be irrigated as fruit is being produced. How to grow pineapple guava Growing pineapple guava from seed is a slow business. It can take a year for seedlings to show any real growth. Most pineapple guava trees are purchased as 1- or 2-year old plants. If you only have room for one specimen, make sure that it is a self-pollinating variety. Most pineapple guavas require a second specimen for pollination. They prefer partial shade, a soil pH of 5.5 to 7.0, and can tolerate some salt spray. They do not respond well to bright, reflected light, so installing pineapple guava next to a driveway probably isn’t the best idea. They can be grown in large containers, and they can also be espaliered or pruned as a small tree, or used to create hedgerows or windbreaks. There are several varieties of pineapple guava to choose from. Caring for pineapple guava One of the best things about pineapple guava is how little care they need. You can ignore them completely, once they are established, or you can give them a boost with these maintenance tips:
Harvesting the fruit Pineapple guava fruit are egg-shaped and can be 3/4 to 3-1/2 inches long. The fruit is described as tasting like a cross between pineapple, apple, strawberry, guava, and mint. Fruit reaches full maturity (and the best flavor) in fall, but it bruises easily. Ripeness can be determined by giving fruit a gentle squeeze. Harvesting fruit too soon is a waste, since unripe fruit is bitter. Waiting for it to fall on its own usually means bruised fruit. Probably the best solution is to set up a net under the tree to gently capture fruit as it falls, but this isn’t alway feasible. Commercially, ‘touch picking’ is used. Touch picking means that if the fruit breaks free when you touch it, it’s ripe. Regularly checking for ripe fruit before it falls will reduce the number of bruised fruit. Some people eat the entire fruit, skin and all, while others cut it in half and scoop the fruit out with a spoon. Pineapple guava no real pest or disease problems. Black scale and fruit flies may show up, but these shrubs are truly trouble-free.
Pineapple guava fruit does not ship well, so most stores never carry it. Adding these trouble-free shrubs to your foodscape means you will have a ready supply of delicious fresh fruit each fall for many years to come. As fruit trees begin putting out fruit in spring, it is your job to take some of that fruit off. It may seem counterproductive. Why on earth would I plant a fruit tree only to take the fruit off when it has only just started growing? Why would you want to reduce your crop that way? Read on and find out! Why thin fruit? Most fruit trees will produce far more fruit than can be supported or made flavorful. Too much fruit and branches start breaking. Now, the tree doesn’t care how the fruit tastes, as long as it tastes good enough to cause animals to help with seed dispersal. To get the sweetness, size, and shape that we want, we have to intervene. Thinning fruit also helps reduce the likelihood of pests or diseases getting established in the nooks and crannies between fruit. Finally, fruit thinning reduces the chance of your tree taking a year off of production (alternate bearing) out of sheer exhaustion. How (and when) to thin fruit trees Different trees have different thinning needs. Generally, the time to thin fruit is dictated by fruit size. Stone fruits are thinned when they reach 3/4 to 1 inch in diameter, while pome fruits can be thinned when they are 1/2 to 1 inch. This is usually in April and May in the Bay Area. You can also predict the time for thinning by noting it 30 to 45 days after full bloom on your calendar. To actually remove the fruit, give it a gentle twist. Sometimes, pruners are needed. Your fruit tree is working very hard at this stage, so be kind. Do not be tempted to thin your fruit trees too early, as this can lead to split fruit later on, especially in peaches. Of course, thinning too late won’t help your fruit become as large as it might have. Fruit thinning by species Some trees do not require thinning. These include cherries, figs, citrus, Bartlett pears, pomegranates, and persimmons. You may want to monitor your persimmons tree, however, as a very productive year can lead to breakage. Use this information to determine just how much to thin, depending on tree species:
Natural fruit drop We are not the only ones who want to protect our fruit trees from breakage due to too much fruit. These trees have evolved to protect themselves with what is erroneously called “June drop”. June drop can occur late spring through early summer and it refers to a fruit tree dropping many immature fruits. Fruits that are diseased or infested may also drop prematurely. Don’t be afraid to get up close and personal with your fruit trees in spring. Thinning fruit will ensure a better crop and a healthier tree. Thinning also gives you a chance to see what’s really going on for your fruit trees, allowing you to halt a minor pest invasion before it causes any real damage. For those of you (like me) who need ways to remember what and how to thin, give this a try: Spring season of thinning, no need to despair
Help them grow stronger with inches to spare Small apricots and plums, give them each two to four Peaches and nectarines, need three inches or more Then muster the clusters of apples and pears Save just the biggest, only one or two there Mutants and mummies and twins all must go Leave only the best. Now just watch them grow! -KR Bacterial spot is a relatively new disease to California.
When bacteria infect a plant, the plant’s first line of defense is often to surround the infected area with a strong barrier. While not always as effective as our immune systems, this often prevents further spread of the disease. These damaged areas usually appear as spots on leaves. Bacterial spot is just one of many different bacterial diseases that attack your plants. First seen in 2006, this particular bacterial spot attacks almonds and other stone fruits, such as peach and nectarine. Bacterial spot (Xanthomonas arboricola pruni) first appears as an amber colored gum oozing from immature nuts. This disease is common in the Southeastern U.S., Europe, Australia, and the Middle East. Bacterial spot symptoms Symptoms first appear mid-April to early May. Damage looks similar to that caused by leaf-footed bugs and anthracnose. Use these notes to differentiate between the three conditions:
Leaves may become spotted, develop angular or circular red lesions, and drop early. If you cut open an affected nut, you will find a pencil eraser-sized lesion. These lesions get bigger, transforming your delicious almond into an orange slime. (Ew!!!) Almond varieties most commonly affected are ‘Fritz’, ‘Monterey’, ‘Nonpareil’, ‘Mission’, ’Neplus Ultra’, and ‘Padre’. How to control bacterial spot Commercial growers use zinc sulfate in the fall to make trees drop all of their leaves, which are then gathered and destroyed. Leaf and mummy removal is followed by spraying with dormant oil and copper treatments, combined with the antibiotic oxytetracycline. Obviously, you are not going to hit your backyard fruit and nut trees with all these chemicals. These tips can help minimize the damage caused by bacterial spot in your garden:
To prevent infection, trees can be treated with oil and copper mixtures before winter. This is yet another reason why it is a good idea to quarantine new plants before installing them. Luscious summer pears are one of the most difficult tree fruits to grow in San Jose, California, but the rewards, for many, are worth it. European pears (Pyrus communis) actually hail from Western Asia and modern day Iraq and Iran. People have been growing pears for over 4,000 years and Bartlett pears have been the standard for over 200 years. In the world gardening and agriculture, that's pretty amazing. Pear varieties
Pears do require a cold rest period, called vernalization, each winter. Silicon Valley only averages 400 chill hours, while Bartlett pears need 800 chill hours each winter. You will need to identify a species suitable to your microclimate. Pears are categorized by the season in which they ripen. Summer pears have thin skins, ripen on the tree in July through September, and most are small to medium sized, and the fruit is fine-textured. Winter pears feature gritty textured fruit that ripens September through November. Below is a list of popular pears with notes, chill hours, and best zones for growing:
How to grow pears Unless you select a self-fruitful variety, you will need at least two trees for a fruit set. Also, keep in mind that full size trees may take up to 20 years to reach full production, while semi-dwarfs take 5 to 8 years. Most bare root stock available in garden centers are 2 or 3 years old. Choose a site that can accommodate the tree’s full size and provide full sun. Pest and disease problems can be reduced by providing good air flow around each tree. Pear trees are best pruned into a “Y” shape. They tend to grow very upright and need trimming to create a healthier, more spread out growth. Pear fruits do not require as much thinning as apples. You can leave 2 or 3 fruits per cluster without problems. Pear pests & diseases More pests attack pears than any other fruit tree in the Bay Area. These pests include aphids, San Jose scale, mites, pear psylla, codling moth, redhumped caterpillars, Eriophyid mites, birds, and squirrels. Common pear diseases include fire blight (Erwinia amylovora), crown gall, leaf spot, pear scab, and apple scab. Pear tree care These seasonal chores can help keep your pear trees healthy:
Pear ripening If you allow your pears to ripen on the tree, you will probably never get to enjoy one. Pears are a favorite food of squirrels and birds. I once lost an entire season’s crop because the squirrels were willing to harvest the pears two days earlier than I was. Pears ripen from the inside out. The easiest way to tell if it is time to harvest a pear is to use the Cradle Test. To do this, cup one hand under a pear and use the other hand to swing the fruit from its 6:00 position to a 9:00 position, with a twisting motion. If the fruit falls, it’s ready. Actually pears taste better if they are harvested when they are mature but not fully ripe. Then place them in the refrigerator for a few days, up to two weeks for summer pears, and 3 to 4 weeks for winter pears. After the fruit has been chilled, bring it back to room temperature and enjoy. Oh, by the way, don’t bruise the fruit at any point in this process. As I said, growing pears is not an easy process. The sweet, juicy flavor of a fresh, properly ripened pear, however, is exquisite. Plum orchards once covered The Valley of Heart's Delight (what is now known as Silicon Valley). Many homes are still graced by individual specimens of these prolific fruit producers, and it is easy to add one to your landscape, as well. Plums are members of the Rose family, in the Prunus genus. This makes them cousins to other stone fruits, such as peaches, nectarines, and cherries. One variety of apricot (Prunus armeniaca) is so closely related that it is actually a plum! Fruits of the plum tree are called drupes. Plum varieties When deciding on a plum variety, keep in mind that plums can be sweet or tart, early or late blooming and ripening, standard size, dwarf, or semi-dwarf. Two varieties are commonly grown are Japanese plum (Prunus salicina) and European plum (Prunus domestica), but there are others. Some European plum varieties do not require cross-pollination, but all plum trees produce far more if there is a second tree nearby. Japanese plums bloom and mature earlier, but European plums tend to be sweeter. Standard plum trees can grow to 30 feet tall and 25 feet wide, semi-dwarfs can be 15 feet wide, and dwarf varieties rarely need more than 10 feet. Plums come in skins of many different colors, from yellow, to red and purple, to nearly black. The interior fruit can be yellow, white, red, or green. Commercially, plums grown to be consumed as fresh fruit are called “sugar plums”, while the remainder are grown to be dried and sold as prunes. Prunes are almost exclusively made from European plums. You can also find plum-apricot and plum-cherry hybrids! How to grow plums
Plums love mild winters and hot, dry summers. While they prefer more sandy soil than many gardens tend to have, they are pretty tolerant of clay, as long as the drainage is good. They do need a lot of sun. Plums are best started from certified disease-free root stock. You can also start a tree from a friend or neighbor’s tree by taking one of the many suckers that tend to appear. Suckers root more easily if they are dipped in rooting hormones (auxins), but they will create their own auxins in a day or so. If starting from seed, plums should be planted 3 inches deep. Be sure to mark the spot so you don’t lose track of your new baby! Plum tree care Plum trees thrive here in warm regions. Trees do require the following seasonal care:
Plum tree pests & diseases The most common plum pests are aphids, mites, and San Jose scale. Other pests include Oriental fruit fly, plum curculio, mealybugs, redhumped caterpillars, green fruit beetles (Cotinis mutabilis), and mealy plum aphid (Hyalopterus pruni). Sticky barriers can reduce the impact of many crawling insect pests. Fungal diseases that affected plum trees include canker, brown rot (Monomania fructicola), and shot hole, also known as Coryneum blight. One of the most common problems faced by plum tree owners is overproduction. Overproduction, or overbearing, can cause broken limbs, so it is important to thin fruit to no more than one fruit every 2 to 4 inches. Don’t be concerned if your plums have a whitish coating on them. This is a protective epicuticular wax known as “wax bloom” and is easy wiped off. Add a plum tree to your landscape this spring for decades of delicious summer fruit and year-round jams and jellies! Over 11,000 years ago, figs were one of our first attempts at agriculture, even before barley, wheat, and legumes. Farmers and scientists had curious ideas about wild and farmed fig trees in those early years. They thought tiny wasps flew from the wild (fruitless caprifig) trees to the farmed female (fruited) trees to help them hang on to the fruit! If that weren’t interesting enough, did you know that figs are not fruit? Read on! The fig tree
Figs (Ficus carica L.) are deciduous trees or shrubs that can grow 30 feet tall. They send out multiple trunks to create a fan-like tree. The wood tends to be weak, so pruning keeps the tree structurally sound. Broad, fragrant leaves provide lovely shade but avoid the sap. It contains a form of latex that can irritate your skin. Fig trees prefer sunny, well drained locations. They can also grow well in poor, rocky soil. These trees are very drought tolerant. Botanically, fig trees are gynodioecious, which means they have hermaphrodite flowers and female flowers on separate plants. You can either buy a self-pollinating variety or multiple trees. It ends up that those ancient farmers were partly correct about fig trees Tiny specialized wasps called Blastophaga psenes pollinate the flowers hidden inside a hollow structure called the syconium. The fruit is technically a scion or infructescence. An infructescence is a fruit head made of the ovaries from a flower cluster. These arrangements are often called false fruits or multiple fruits. Within each fig “fruit” are several one-seeded fruits called druplets. Pineapple, wheat, and corn are other examples of infructescence. How to grow figs Originally from the Middle East and western Asia, these resilient trees grow well in regions with hot, dry summers and cool, wet winters. Figs reproduce in several different ways. Naturally, birds and mammals that eat the fruit end up spreading seeds. Fig trees also tend to send out aggressive roots, stolons, and suckers that can generate new plants. You can bend a low-growing branch down to the ground or a container, hold it down with a rock or some wire, and wait for roots to grow. After roots emerge, you can separate it from the parent plant. Most buy fig trees as bare root trees. Fig trees can be grown in large containers, but you will want to take advantage of their deep roots. Planting fig trees in the ground practically eliminates the need for irrigation. Like grapes, fig trees have deep roots that allow them to get most of their water from the soil’s saturation (or phreatic) zone. Fig pests & diseases Thrips, ants, green fruit beetles, dried fruit beetles, gophers, and birds are the only serious pests. You can thwart ants with a sticky barrier around the trunks. Netting is invaluable for protecting fig crops. Eriophyid mites do not cause significant damage, but they can carry fig mosaic. Whitewash the trunks to protect them from Sunburn damage. Just paint a 50:50 mix of water and white later (not enamel) paint on exposed surfaces. Some fig varieties produce two crops a year. The first, or ‘breba’ crop, occurs in mid-summer. The second main crop ripens in late summer or fall. Be sure to allow figs to ripen on the tree. They will not continue to ripen once picked. Forget the bagged, dried version of this healthful fruit. Plucking a freshly ripened fig from the tree and taking a bite is heavenly. You can always dry your own. Add figs to your foodscape for decades of delicious fiber and welcome summer shade. Hazelnuts, filberts, or cobnuts, whatever you call them, these delicious nuts grow on trouble-free shrubs that make excellent additions to your foodscape. Since hazelnut shrubs naturally grow alongside creeks and under taller overgrowth, they are a good choice for locations with partial shade. Why grow hazels? The obvious reason for growing a hazel bush is the delicious nuts. Hazelnut plants can produce food for 80 years! Hazelnut shrubs also make excellent, drought tolerant anchor plants in the landscape. Traditionally, hazels were planted as hedgerows between properties and grazing fields. They were frequently coppiced, or cut to ground level to stimulate new growth, to provide long, slender poles for basket-making and wattle and daub fencing.
How hazels grow
Unlike most plants, hazelnuts bloom and pollinate in winter. Yellow pollen-crusted catkins release their bounty to the wind, which carries it to tiny red flowers. There, the pollen stays dormant until summer. That’s when the nuts start to form. Hazels are monoecious, or hermaphroditic, having both male catkins and female flowers on the same plant. Catkins are hanging flower clusters that contain pollen. Hazelnuts are self-infertile, which means you will need more than one plant to produce a crop of edible nuts. Members of the hazel family are all deciduous. Some are trees and some are suckering shrubs. These suckers can be used to to create new shrubs elsewhere on your property or given to family and friends to start their own. Commercially, the suckers are generally removed and the shrub is trained into a tree form, to make management and harvest easier. What you do with yours is entirely up to you, but it is nice to have options! How to grow hazelnuts If you have access to suckers, use them! Otherwise, you can plant nuts in loose soil and water occasionally. Germination rates and speed can be increased by scarification, or scoring the outer layer of the nut. Once seedlings are 12 inches tall, they can be transplanted to their permanent location. They will begin producing nuts in their 3rd or 4th year. These nuts grow in clusters called burrs. Hazels are shallow-rooted plants that cannot tolerate soggy ground. They are drought tolerant and require little effort on your part, once they are established. Only during the peak of California summers do they need any irrigation. Hazelnut pests and diseases One very serious threat to hazelnuts has kept them from being grown commercially in the Eastern U.S. It is called eastern filbert blight. Our native species are resistant, and some are immune. This disease has recently made its way west to Oregon and California. Pests include bud mites, jay birds, and squirrels. Ads claim that giant eye floating balloons are a good way to keep birds out of fruit and nut trees, but I was unable to find any research that verified those claims. Harvesting hazelnuts Hazelnut harvesting begins in autumn, as the leaves and burrs turn brown. Remove nuts from the burrs and lay them out in a single layer, in a protected area, to dry for a few days. Roasting makes it easy to remove the inner paper, which can taste bitter, and it brings out that rich hazelnut flavor that we all know and love! Sweet, flavorful apricots, warm from the sun, freshly plucked from the tree, are one of life’s perfect moments. In my opinion, they rank right up there with their cousins, peaches and nectarines, as foods that define summer. Apricots (Prunus armeniaca) are also related to cherries, plums, prunes, and almonds. If you look at the pits, you will see the similarities; they are all stone fruits. While dwarf varieties can be grown in large containers, apricots prefer being planted in the ground, in a sunny location. Plant an apricot tree and you will be treated to lovely spring blossoms and delicious summer fruit. The trunk will, over time, develop a striking gnarled look, too.
How to plant an apricot tree Unlike apples, pears, and other members of the rose family, apricots grown from seed have a higher chance of being similar to the parent plant. While there are no guarantees, you can take the pit from an apricot, cover it with an inch of soil, keep it watered and in a sunny location to start your homegrown apricot tree. For faster results, bare root stock can be used. Apricot bare root stock should be planted in January or early February, here in the Bay Area. Apricots prefer well-drained soil, but they can tolerate some clay. Before placing your apricot rootstock, be sure to amend the site with lots of compost, to help it get a healthy start. Also, if you have heavy clay, be sure to score the edges of the planting hole. Smooth clay is an impenetrable barrier to young roots. How to select an apricot tree When selecting rootstock, be sure to match the variety with your microclimate. Chilling hours vary by species, as does disease and pest resistance. If your tree does not accumulate enough chill hours, you won't get any fruit. Most apricots are self-fertile, so it is usually not necessary to have more than one tree. Contact your local Cooperative Extension Office for the best varieties for your area. The following varieties are good choices for warm weather regions:
Apricot tree care Each fall, before the rains begin, prune away 20% of last year’s growth, along with any dead, diseased, or poorly placed branches. This will allow more light to reach interior branches, stimulate new spur development, and improve the overall health of the tree. [Spurs are flower-bearing buds]. Spray for pest and disease control in winter and again in spring. Feed mature apricot trees 1 to 2 pounds of urea just before spring irrigation is begun and water it in thoroughly. Young trees should be given the same amount of urea, but spread it out in quarters over a 4 month period. As fruits reach 1/2 inch in diameter, they should be thinned to one fruit every 4 to 6 inches, for the best size and flavor. This also reduces the likelihood of pests and diseases. Irrigating apricots Begin irrigating in spring by watering every 2 or 3 weeks to a depth of 18 to 24 inches. This is one of those times where guessing isn’t good enough. I use my soil sampler, but you can use a trowel to gently dig down to the appropriate depth. If the soil isn’t moist, you need to figure out where the water is going and redirect it. Many times, hydrophobic soil will push water away. Watering more slowly can avoid this problem. Apricot pests and diseases Peach twig borers, Fuller rose beetles, San Jose scale, mites, and aphids are common apricot pests. Apricot is susceptible to Eutypa dieback, so pruning should only be done during summer, unlike other trees which are pruned during winter dormancy. Autumn and winter sprays of dormant oil, fixed copper, or Bordeaux mixture, as well as the use of sticky barriers, can help protect your apricot tree against other pests and diseases, such as brown rot, bacterial canker, shot hole disease, and crown gall. Despite these fungal diseases, do not use sulfur on apricots. A little space in your yard or on a balcony is all that is needed to start growing fresh apricots - give it a try! The seeds from this tree may not be edible, but they are certainly a natural way to cut down on your laundry bill! This discovery started when I was looking for a laundry detergent that wouldn’t hurt my landscape. I have a large diameter vinyl hose attached to the back of my washing machine (in summer) and I use the water to irrigate my fruit and nut trees, lawn, and ornamentals. (This isn’t legal everywhere, and isn’t necessarily a good idea, depending upon your preferred brand of laundry soap.) In my search for living a less polluting (and more cost effective) life, I stumbled upon soapnuts, also known as soapberries. Believe it or not, I was delighted to discover that these tree fruits cleaned my laundry just as well as commercial soap! Not only that, but they have natural fabric softening properties.
What are soapnut trees?
Soapnut trees are members of the Lychee family (Sapindus), which includes 5 to 12 different species of trees and shrubs (depending on who you ask) that all produce saponins. These saponins are found in the fruit, or drupes, of the soapnut tree (as well as in soapwort plants and sea cucumbers). Saponins are surfactants, chemicals that reduce the surface tension between molecules, allowing water to lift away grease, soil, and other impurities from your laundry. In fact, people have been using soapnuts as a sudsy cleaning agent for far longer than commercially made soaps and detergents. The soapnuts used to clean laundry, hair, and skin nowadays are mostly from the S. mukorossi variety. This particular tree also goes by the names Sapindus detergens, Indian soapberry, Chinese soapberry, Reetha, Areetha, Ritha, and Doda, just to name a few. [If you are feeling particularly nerdly today, you can see this plant’s genetic code here.] How soapnut trees grow Soapnut trees prefer temperate to tropical conditions. Some varieties are deciduous, while others are evergreen. The Indian soapberry tree, in particular, is a lovely deciduous tree that can tolerate poor soil. Trees will need the equivalent of 60 to 80 inches of rainfall each year. (San Jose, CA gets an average of 15 inches of rain, so some irrigation will be needed in the Bay Area.) Ultimately (and under ideal conditions), your soapnut tree can reach a height of 80 feet, with a girth of 15 feet. Most trees, however, end up significantly smaller than that (12 to 16 feet tall). The tree has smooth gray bark and a semi-umbrella shape. Small, greenish-white flowers emerge in summer and fruit appears in July and August. A mature soapnut tree can produce 60 or more pounds of soapberry fruit each year. How to grow a soap nut tree To grow your own soapnut tree, you will first have to find a seed. This has become easier in recent years, as more people discover just how effective soapnuts are. You can search online for seeds, or you can give soapnuts a try and hope to find a seed. The drupes (pictured) normally contain up to three seeds. The seeds need to be roughed up a little (scarified) before they can germinate. It is best to plant in spring. You can use a fine-grit sandpaper to score the outer hull, then soak the seeds in warm water for 24 hours. The most common way to keep the water warm is to place the seed and the warm water in a thermos. (My guess is that these prerequisites evolved out of the natural processes of seeds being eaten and then, well, you know.) Start each seed in a large container filled with high quality potting soil, planting them one inch deep. Keep the soil moist down to at least 2 inches, but not waterlogged, and provide plenty of sunlight. It may take a long time for your seeds to germinate. Once they do, they will grow quickly. After 3 or 4 months (or when frost isn’t expected any time soon), you can place your soapnut tree in the ground. Select a site that provides partial shade or dappled sunlight, if possible, and plenty of room to grow. Using homegrown soapnuts Once your soapnut tree produces fruit, you will want to collect the drupes in early winter, remove the seeds, and allow the fruit to dry out. A small muslin bag with tie strings can be used to hold 4 or 5 soapnuts and tossed in the laundry. The soapnuts do not have to be removed for the rinse cycle because the normally colder water of rinse cycles does not pull as much of the sudsing saponins as warm or hot wash water. The same bag of soapnuts can be used for up to 10 loads of wash. After that, toss them into the compost pile and reuse the bag! Other advantages of soapnuts Besides being disease-resistant plants, soapnuts also have gentle insecticidal properties that have been shown to interfere with mosquito and lice life cycles. Whether this means that washing your clothes with soapnuts will render them mosquito-proof has yet to be shown. Did you know that soapnuts are used to clean cardamom seeds, improving their color and flavor? If you use graywater from your washing machine, soapnuts are a far better option than soaps and detergents sold over-the-counter, and they’re free! Unfortunately, it may take your soapnut tree up to 10 years to begin producing fruit. (At least it’s faster that stone pines!) The nice thing is, soapnuts are lovely trees, long before they provide you and your family with a lifetime supply of environmentally safe laundry soap and shampoo! Growing apples is highly rewarding, but don’t try starting one from seed. These particular fruit trees are known as extreme heterozygotes. In plain English, the offspring are nothing like their parents. Planting seeds from a Red Delicious apple will not produce apples that look or taste like that shiny red fruit. It may not taste good at all. Most modern apple trees today are propagated from cuttings grafted onto sturdy rootstock. [Did you know that apples are related to roses?] Apple history Apples (Malus pumila, aka Malus domestica) have a rich and varied history. They hold a place in nearly every culture and religion, being one of our earliest attempts at tree cultivation. But wild apple trees (Malus sieversii) bear little resemblance to their domesticated progeny. Wild apple trees, still found in central Asia, can grow 40 feet in height, and the fruit is smaller and more tart than most people find palatable. Most of the apples sold in grocery stores are crosses between Malus pumila and crab apples. There are currently more than 7,500 apple cultivars with various traits of skin color, texture, disease and pest resistance, juiciness, storage ability, and more. In 2010, the entire apple genome was mapped, with over 57,000 genes identified. [Humans are estimated to have up to 25,000 genes. I guess we must be just one big family then.] Bare root apples The best way to start growing apples is with bare rootstock. Some apple varieties require cross-pollination, while others are self-pollinating. If you only have room for one tree, you need a self-pollinating variety, or all you will get is summer shade. Plant your bare rootstock during late winter or early spring. Before you buy, however, you may want to conduct a soil test with a reputable lab. This inexpensive test is an excellent investment in a tree that will probably live and produce fruit for the next 100 years. Also, consider the size of your mature tree - it is far easier to pick apples and care for your tree if it is a dwarf or semi-dwarf variety. Chill hours Chill hours are the accumulated time spent between 32°F and 45°F each year. In this temperature range, the growth-inhibiting hormone responsible for dormancy begins to break down, allowing trees and shrubs to start producing the buds that become the leaves and flowers of spring. The flowers and buds do not form properly unless enough chill hours occur. The number of hours needed is species-specific, so you need to know how many chill hours occur, on average, in your yard before selecting a tree variety. Red apples generally need 1200 to 1500 chill hours to develop their color and flavor. Green apples need less. How to grow apples Apples grow best in well-drained, nutrient-rich soil with full sunlight. Apple trees need some space for good airflow. Full-sized trees will need a 20-foot circle of space, while dwarf varieties need only 10. Dwarf apple trees tend to overproduce, breaking branches, so you may need to do more pruning or provide tree support. You can grow dwarf apple trees in containers. Once your bare root tree arrives, dig a hole twice the diameter of the spread-out roots and as deep as the root ball. Failing to plant trees at the proper depth is the main cause of tree deaths. Remove any grass or weeds growing within two feet of this circle. Remove any dead, damaged, or diseased roots, and then soak the rootstock in a bucket of water for a couple of hours or overnight if they are dried out. Mix some aged compost with soil from the hole and spread it out in the bottom of the hole. Be sure there are no smooth edges in the hole. Heavy clay and other compacted soils can create impenetrable barriers to young roots. You can help your apple tree get a better start by roughing up and scoring the edges of the planting hole. Place the tree in the hole, ensuring that the graft union (where the rootstock joins the scion) is at least 2 inches above soil level to avoid crown rot and other fungal diseases. Resist the urge to tamp down the soil. To eliminate big air pockets, "mud in" your baby tree by watering heavily at planting time. Seasonal apple tree care Winter apple tree care includes pruning 15 to 20% of the previous year’s growth, allowing more light to reach the middle of the tree, removing dead or diseased branches, and spraying dormant oil to control San Jose scale, and aphid and mite eggs. In spring, treat apple trees with a fungicide to help prevent powdery mildew and apple scab. These treatments should occur when the twig tips first green, when the buds are pink, and then every ten days until the rainy season ends. Thin the tiny fruits to one every six inches for better growth and flavor. If apple maggots or codling moths have been a problem in previous years, bagging the fruit or coating it with kaolin clay are organic methods of protecting your valuable crop. Before you start irrigating a mature apple tree in spring, feed it with two pounds of urea or 40 pounds of aged manure. Summer chores include feeding young trees 20 pounds of aged manure or 8 ounces of urea every month and watering it in. (If you use drip emitters, be sure you do not use more than 1 ounce of urea per emitter per application.) Spray for codling moths from late spring to the end of summer, and monitor for aphids and mites. Irrigate trees every 2 to 3 weeks. As you pick ripe apples, watch for and remove any mummies you come across. After harvesting, fertilize mature trees the same way you did in summer. Remove all leaves from around the tree and compost them to help prevent apple scab. Mulching around (but not touching) your apple trees will reduce weeds, stabilize temperatures, and provide the slow release of nutrients.
Apple pests and diseases Few pests or diseases will kill an apple tree outright, but it has many attackers. The use of sticky barriers around the trunk will halt some, such as ants, slugs and snails, and Fuller rose beetles, but most apple problems come in on the wind. Stem blight, crown gall, leaf spot, powdery mildew, fireblight, and other bacterial blights are common diseases of apple trees. Cedar apple rust can also occur if apples are grown near Eastern red cedar trees. Also, apples share a susceptibility to bacteria blast with lilacs and stone fruits. Common pests include codling moths, apple maggots, San Jose scale, redhumped caterpillars, armyworms, and Eriophyid mites. New to the apple scene is another pest, chili thrips. Also, any local fog can cause more russeting. Russeting is when the apple skin turns brown and rough. Find a spot in your landscape for one of these beauties because plucking an apple from your very own tree and taking a bite, well, it's just one of life's finer experiences. And we all want to keep that doctor away! Navel orangeworms attack far more than oranges and other citrus. They can seriously reduce your backyard apricot, almond, walnut, pomegranate, pistachio, date, fig, pear, apple, and stone fruit harvests. You can protect your fruit and nut crops by learning more about this orchard pest. Navel orangeworm moths (Amyelois transitella) can fly in, deposit eggs, and be on their way in a matter of minutes, so monitoring regularly can go a long way toward protecting your foodscape. Navel orangeworm description Navel orangeworm eggs start out white. In 4 to 23 days, depending on temperature, the eggs will turn orange just before they hatch. The larvae are off-white or pink grubs with a dark head. If you look closely, you may be able to see a couple of crescent-shaped marks on the second segment behind the head. Adult moths are just under 1/2 an inch long, grayish brown, with irregular silver and black wing markings, and a snout-like appendage on the face. Navel orangeworm lifecycle Adult moths are generally present from March through October in California, and females begin laying eggs two nights after they emerge! Those eggs are laid on mummified fruits, newly forming fruits, and on freshly splitting almonds. The first instar burrows into a nut or fruit, where it, and future instars, will feed extensively. Next, the larva pupate in a webbed cocoon within the fruit or nut. Damage caused by navel orangeworms These orchard pests will devour an entire almond in the shell without ever being seen. If you examine an infested fruit or nut, you will see tiny entry holes and lots of frass and webbing. As they feed, navel orangeworms also provide entry points for fungal diseases and other pests. Orangeworm control
You can protect your crops from navel orangeworm infestation by irrigating trees throughout the summer and by harvesting early and frequently. As always, remove mummies immediately and completely, every time they are seen. I have learned that there is a parasitic wasp, Goniozus legneri, that is supposed to be effective and commercially available. As soon as I can track down a source, I will provide an update. Crop protection Once infested, citrus fruits are pretty disgusting, so you will probably want to toss them in the trash. After harvesting almonds, pistachios, or walnuts, navel orangeworm eggs can be killed by freezing the nuts for 48 hours. After that, nuts can be stored at room temperature in airtight containers. Stone pines, or pinyon pines, are commonly used as live Christmas trees and they produce delicious (and expensive) pine nuts. As far as conifers go, the stone pine is my favorite, simply because of the pine nuts they produce. No pesto is the same without the sweet, nutty flavor of pine nuts. They make scrumptious pine nut bars, too! Stone pines (Pinus pinea) were originally from northern Africa and are now found in the Mediterranean. People have been enjoying pine nuts since, well, since there have been people! We have actively cultivated these high protein treats for over 6,000 years.
How stone pines grow
Like most conifers, stone pines grow from seeds found in a cone. This makes them gymnosperms. Stone pine seeds take 3 years to form - longer than any other pine. As juveniles, stone pines are bushy and round, with a bluish tint. The needles are short (3/4 to 1-1/2 inches long) and singular. As trees reach 4 or 5 years of age, mature needles begin to emerge. These older, darker needles are longer (7 to 8 inches long), and held in bundles of 2, 3 or 5. By the time the tree is 10 years old, all the needles will be the longer variety, unless the tree is responding to an injury. Mature trees have an umbrella shape, with a canopy that can reach over 25 feet. They are sometimes called umbrella trees for this reason. They are also known as Italian stone pines. Stone pines prefer full sun and well-drained soil. Once established, they rarely, if ever, need any irrigation, pruning, or fertilizer. Stone pine pests & diseases The western conifer seed bug, aphids, pine shoot moths, bark beetles, Eriophyid mites, mealybugs, weevils, and adelgids (an aphid cousin) are common pests. Many of these pests feed on the sap, stealing valuable nutrients and moisture from the trees, causing distortion, susceptibility to other diseases, and even death to the tree. Honey fungus, or Armillaria root rot, Pine needle cast, canker diseases, Botrytis blight, needle blight, root rot, crown rot, and rusts are common pine diseases. Fair warning Before you jump to buy yourself a stone pine tree with visions of pine nuts dancing in your head, you need to understand that there is a reason why pine nuts cost about the same, per pound, as your finest cut of beef. Getting those nuts to the point where they are edible is very labor intensive. Also, your stone pine will not produce edible seeds until it is 10 to 12 years old. As green cones begin to open, you will need to smash the bejeezus out of them to get the cones to release the nuts. This is commonly done in burlap sacks with baseball bats. Then you get to hand sort through all that pine cone debris to find the dark paper-coated pine nuts. That dark paper is yet another layer that must be removed. This takes a lot of time and patience, and is why most of our $19 a pound pine nuts come from China, where cheap labor makes it financially feasible. Unfortunately, the variety of stone pine grown in China (Pinus armandii) has been shown to leave a metallic taste in your mouth that can last for a couple of days. So maybe all that time and effort is worth it after all… Did you know that the fruit of a pomegranate tree is a berry? That’s if you ask a botanist. Like other berry plants, pomegranates (Punica granatum) have spiny branches and delicious fruit. When I was a child, growing up in the San Fernando Valley, there was an empty lot down the street. On that lot was a giant old pomegranate tree. It had grown up and out and down, almost like a willow, creating a magical circular space underneath. No one could see us from outside the tree, the growth was so thick! We would pick sun-ripened pomegranates from the outside of the tree and then enter our Secret Clubhouse, where we would tell stories and make wild guesses about growing up, as we munched on the sweet-tart fruity seeds. These healthful fruits are perfectly suited to growing in drought-prone areas. With a small initial investment of time, money, and water, your family can enjoy fresh pomegranates for many years to come. Pomegranate varieties Before you buy a pomegranate tree, be sure that the variety you are buying is an edible and not an ornamental. There is no sense dedicating space and water to an inedible variety when you can have an edible! Pomegranates grow in a variety of colors and sizes. Rinds can be red, yellow, pink, orange, green, and even black. Some varieties have seeds that are very hard, while others are softer. The most popular cultivars in California are ‘Wonderful’, ‘Granada’, and ‘Foothill’. The later two are early season varieties. UC Davis offers a helpful Pomegranate Cultivar Chart to help you select the best variety for you and your family. Both ornamental and edible types can be self-pollinating or cross-pollinated by hummingbirds and insects. It takes a pollinated flower up to 7 months to produce an edible fruit. How to grow pomegranates Pomegranates are a very tolerant plant, when it comes to soil types and irrigation. They prefer full sun and hot summers, but they can handle some partial shade. Pomegranates will founder in wet soil or full shade, so choose your site accordingly. Pomegranates can be grown from seeds, but it will take a few years before you get any fruit, and pomegranate seeds do not always grow true to the parent plant. You can also plant rooted cuttings or bare root trees. Grafting does not work for pomegranates. Newly planted trees should be watered every day until new growth is seen. Then water only once a week (assuming it doesn’t rain). Keep weeds away with mulch, just be sure the mulch stays 6 to 8 inches away from your pomegranate. Pruning pomegranate
Pomegranates are deciduous trees that can grow up 30 feet in height and 15 feet wide (most are 6 to 12 feet tall). Pomegranates produce fruit on second-year wood, so you will want to make sure that you leave some of the last year’s growth when pruning. Pomegranates can be pruned as full-sized trees, hedges, landscape anchors, or shrubs. They can also be grown in containers. You can even create bonsai and topiary from pomegranate! Pomegranate pests & diseases Like tomatoes and citrus, pomegranates are susceptible to citrus fruit split. Other diseases that can turn up include Alternaria rot, Armillaria root rot, Botrytis blight, and other fungal diseases, especially if plants are over-watered. Common pests include whiteflies, fruit flies, ants, cotton aphids, mealybugs, soft scales, leaf-footed bugs, and the pomegranate butterfly. Eating a pomegranate Those little seeds are tasty, but getting to them can be a pain. The easiest way I have found is to cut the fruit in half, hold one half peel side up, over a bowl, and beat the bejeezus out of it with a wooden spoon. The seeds fall out and the rest of it tends to stay put. It is easy to remove any other debris simply by adding water to the bowl: the fruit sinks and everything else rises. Viola! Pomegranates grace holiday tables, a symbol of prosperity, but you can add them to your yard or balcony for some prosperity of your own! Isn’t this the weirdest lemon you have ever seen? This fruit has been infested by the citrus bud mite. Just as the name implies, citrus bud mites (Aceria sheldoni) attack those fragrant citrus flowers and buds, causing a distorted rosette growth pattern of the surrounding leaves, flowers, and fruit. These pests are normally found on lemons and other citrus grown in coastal regions, but Southern California has been seeing them move inland, so they will probably become more of a problem here in the Bay Area before long. These citrus pests are really tiny. They can only be seen with a 20x hand lens or under a microscope. Citrus bud mites have a tapered yellow or pink body and four legs that look like they are growing out of its head. [For anyone who has read this blog for any time at all - these bizarre descriptions are surprisingly normal - fiction has nothing on real life!] These pests are active year round. Each summer, females lay up to 50 eggs in the tiny scales that are supposed to protect tender new buds. When the eggs hatch, the young go through 4 instars before maturing. Commercially, citrus bud mites can be a real problem, but most home orchards only see a few affected fruit, and it is still edible. [I’ll bet horizontal slices would actually look pretty amazing… but peeling it would be a nightmare!]
The real problem with these pests is that the distorted shapes caused by their feeding create the perfect hiding spot for other citrus pests, such as citrus mealybugs and the two-spotted spider mite. Researchers have tried using horticultural and dormant oil treatments and found them ineffective, since the pests are in a protected space. If signs of citrus bud mites are seen, you may simply want to monitor fruits for signs of other pests who are taking advantage of the prime real estate. Have you ever had citrus bud mites in your fruit? I would love to see photos! Have you ever tried eating an orange that looks ripe but ended up being very unripe? Major pucker factor! Your orange may have been infected with alternaria rot, a fungal disease that attacks lemons and navel oranges, causing the fruit to change color before they are ripe. Citrus affected by the Alternaria citric fungus may look perfectly ripe and ready on the outside, at first. After fruit is harvested, the fungi continue breeding and feeding on the inside. By the time the infection is fully established, the stylar (flower) end of the fruit may show a dark brown or black area. Alternaria rot is also called black rot when it appears in navel oranges. If you cut infected fruit in half, you will see the rotted area has spread into the core of the fruit.
There are several varieties of the Alternaria citric fungi. Most of them do not produce toxins (but you still won’t want to eat the fruit). So, how can you prevent or treat alternaria rot? First, healthy plants are better at protecting themselves. Navel orange trees experiencing citrus fruit split and water stress are going to more vulnerable to infection that trees which have received regular irrigation. Fungicides are generally ineffective. Remove infected or otherwise damaged fruit and delay harvesting for as long as possible. This will allow infected fruits to show themselves and be be disposed of, before harvesting the unaffected fruit. Highly refined horticultural oils are sprayed onto plants as a pesticide. They are used to control mites and insect pests, and to prevent some fungal infestations.
When oil was first used to combat garden and agricultural pests, heavier “dormant oils” were used in the winter, while trees were dormant and leafless, and lighter “summer oils” were used when leaves were present. While both varieties are now much more refined, believe me when I tell you that using dormant oil on leaves in summer is a really bad idea.
Types of horticultural oil Horticultural oils can be petroleum or plant based. Currently, the petroleum-based horticultural oils provide better coverage without damaging leaves. Most over-the-counter varieties are made from petroleum. Vegetable oils, such as sunflower, soybean, and cottonseed, provide good insect control, but phytotoxicity is a still a problem. Phytotoxicity is anything that is poisonous to plants. Research is continuing. At this time, only Neem oil is a consistently safe vegetable-based horticultural oil, but it acts differently than other oils by adding a naturally occurring chemical to the mix that makes insects ‘forget’ to eat or breed. How to apply horticultural oil Horticultural oils are best used when pests are vulnerable. Soft-bodied pests, such as aphids, can be sprayed as populations become troublesome. Scale insects are most vulnerable in the crawler stage, while caterpillars and spider mites are best managed as eggs, in winter and early spring. Heavy infestations of scale insects may require repeated sprayings through June. Once pests have reached a protected stage of growth, such as the hard shell covering over adult scale insects, horticultural oils are not effective. Also, the oil must coat pests completely to work. WARNING: When applying horticultural oils, it is important that sulphur is not present. Horticultural oils should not be applied 2-4 weeks before or after a sulphur treatment, depending on who you ask. Also, horticultural oils should not be used on water stressed plants. Many horticultural oils are mixed with other ingredients, such as fungicides or insecticides, so it is very important that you read the label and follow the directions exactly, to avoid causing more harm than help. Most horticultural oils are considered appropriate for organic farming. |
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