We should all have such problems…

Here, in North American, smooth sumac (Rhus glabra) and stag horn sumac (R. typhina) are used to make a drink called “sumac-ade”. The cashew family also includes mastic trees (Pistacia lentiscus) and varnish trees (Toxicodendron vernicifluum), which are the trees that give us varnish, lacquer, and useful oils. Natural varnish is made from tree resin.


Like many other families, there is heated debate about who belongs and who does not. Not too long ago, pistachio plants were brought into the cashew fold, but there are still discussions about this in scientific corners. Cashew family taxonomy includes dozens of genera, most of which are not edible. Watch out, though - some of them might try to hurt you!


Cashews - beware!

Did you know that raw cashews are poisonous? They are. They contain the same chemical found in poison ivy, poison oak, and poison sumac. That’s because they are all in the same family! The sap of all cashew family plants, called urushiol, is something to be reckoned with as it can be highly toxic. Just under the bark, these plants have resin canals filled with the stuff. ​

If that weren’t bad enough, the seed coat of cashew drupes contains a toxic oil that is acidic enough to burn your skin. If you are still interested in growing your own cashews, read on. If not, read on anyway! Who knows what you’ll learn?


How to grow cashews

Being native to tropical and subtropical places such as India, Thailand, Sri Lanka, and Papua New Guinea, cashew tree might be difficult to grow, depending on your Hardiness Zone. If you are determined, however, it can be done. Keep in mind, before you get started, that mature, full-sized cashew trees can grow to nearly 50 feet in height. Dwarf varieties are far more manageable at only 20 feet.


Cashew trees prefer loose, sandy soil with plenty of sun and excellent drainage. Do not try using grocery store seeds - they are not viable. You will need to get seeds from a reputable supplier. Viable seeds should be planted 4 inches deep and about 30 feet away from each other. These plants can handle temperatures as high as 122°F, but cold and damp will be the death of them. Heavy, soggy clay soil nearly always causes root rot in cashew trees. They don’t handle wind very well, either, so be sure to provide tree supports while trees are young and do not plant them in windy areas.


Keep your young tree properly irrigated and feed trees twice a year using a mix determined appropriate by your soil test results. Generally speaking, cashew trees use a lot of nitrogen, phosphorus, and zinc. After 3 or 4 years, you should be able to harvest your first crop of cashews. You will know your crop is ready to harvest when the cashew apple is either red or yellow and the drupe shell has turned gray.

"Leaves of three, let it be; berries white, take flight; root hairs red, recoil"
​
[I made up that last bit.]

Who knew apples could get the measles?


Unlike the human variety, which is caused by a virus, apple measles is a symptom of manganese toxicity.

Symptoms of apple measles

The first sign of apple measles is tiny red pustules on new twigs. If you look closely, you can see that the tissue in the center of each pustule is dead. Take a look on the inside of the twig and you will see that the lesion spreads, under the bark, into the cortex or the phloem tissue.  If you take a cross-section of the twig, you will see brown streaks or flecks. As the affected twig matures, the bark thickens, cracks, and sloughs off, leaving flakey cankers. This flaking off of bark can last for several years.


​Treating apple measles

Since apple measles is a symptom of too much manganese in the soil, you need to alter the soil chemistry to help your apple tree. Apple measles occurs most commonly in acidic soil, so increasing the soil pH with lime or other alkaline soil amendment will help reduce future damage.


Unfortunately, it is very difficult for trees to recover from apple measles, so get your soil tested every 3 to 5 years, so you know what they are dealing with - before the damage is done.

Kumquats are members of the rue, or citrus family.


Native to south Asia, kumquats have been cultivated since the 12th century. Unlike oranges, or their giant cousins the grapefruit, kumquats are closer in size to olives. These somewhat tart fruits can be eaten whole, candied, chopped into a relish, fermented into a liquor, or cooked into a delicious marmalade.. These somewhat tart fruits can be eaten whole, candied, chopped into a relish, fermented into a liquor, or cooked into a delicious marmalade.

Kumquats can be grown in containers. Container grown kumquats can grow to 6 feet and produce fruit, if they are fertilized regularly.


Kumquat pests and diseases

Asian citrus psyllid is the most serious threat to citrus trees, as they can carry huanglongbing, a fatal disease. The diaprepes root weevil may also become a problem. Leaf miners, aphids, scale insects, and whiteflies are far more likely. Citrus diseases, such as armillaria root rot, alternaria rot, anthracnose, brown rot, citrus blast, exocortis, and phytophthora root rot may occur. Kumquats tend to be resistant to citrus canker and most citrus trees thrive in the Bay Area.


Consider adding kumquats to your foodscape this year for a lifetime of fragrance, color, and Vitamin C!

This may seem like too much information to be useful, but let’s walk through a few examples together, so you can see how to better prune your trees.


Almonds

You can see that almond trees produce the majority of their fruit on lateral spurs, and some fruit along lateral shoots. You will also see that each spur is good for 5 years, that very little pruning is needed, and that almond trees are best trained in the open center system. So, what does all this mean to the owner of an almond tree?


First, snipping the tips off of anything on an almond tree won’t harm nut production. Of course, if you snip too much, the tree will have to put energy into healing, rather than filling your hopper with delicious almonds. The open center system is exactly what it sounds like - the center of the tree is left clear of major branches in the middle, creating a bowl shape which allows for plenty of sunlight and air to move through. ​


​Apples

Looking at the information for apples, you can see that snipping off the ends of all the spurs would leave you without much of an apple crop, but cutting off the ends of long shoots would only have a very slight impact.


​Persimmons

Now look at persimmons. All of the fruit production occurs on long shoots of new wood. Cutting out all of your new growth would hamper fruit production. The same is true for quince. Figs are produced on new wood and one-year old shoots.

Generally speaking, citrus trees do not need to be pruned to improve fruit production.


If you sort the chart by location of major fruiting buds, you have:

•     Lateral long shoots — fig, nectarine, peach, persimmon, and quince
•     Terminal long shoots — young walnut
•     Lateral spurs - almond, apricot, cherry, and plum
•     Terminal spurs — apple, pear, and mature walnut

Armed with this information, go outside, sanitized pruners in hand, and see where you can prune your fruit and nut trees for improved overall health and a significant increase in production!

Blossom brown rot looks similar to brown rot (Monilinia fructicola), affecting flowers from the pink bud stage through petal fall. All parts of the flower are susceptible.


Symptoms of blossom brown rot

The first sign of blossom brown rot is the death of young flower blossoms. What should be a colorful, flower-laden tree buzzing with pollinators looks more like sticks with clusters of brown, dried-up tissue paper. [That would be an extreme case.] More often, infected flowers are intermittent (at first). Gum may ooze from the base of infected flowers, and cankers may form on twigs. Those cankers will have tan centers and dark edges. Blossom spurs and their leaves may collapse. Under humid conditions, you may see tan to gray spore masses.

​
Blossom brown rot life cycle

Fungal spores overwinter in twig cankers, on mummified fruit, and on any diseased flowers that remain attached to the tree. As temperatures rise in spring, fungal spores begin populating nearby twigs and other blossoms, causing twig and branch dieback and blossom losses. Spores are airborne and spread by irrigation, splashing raindrops, and insects.


​How to control blossom brown rot

​This fungus thrives in rainy weather with temperatures in the 70s(F). High humidity can also encourage spore development. Growth is almost directly related to local humidity and temperature levels, which can be tough to control in the home garden.


Proponents of compost tea recommend foliar sprays as a treatment for blossom brown rot, but research has shown that compost tea either has no effect or worsens the condition.


Unless you want to apply chemical fungicides, you are best off selecting varieties that are resistant to this disease in the first place. The following species of almond tree are most susceptible to blossom brown rot: Butte, Carmel, Drake, Ne Plus Ultra, Winters, and Wood Colony.


You can also reduce the likelihood of blossom brown rot by removing any mummies as soon as they are seen and disposing of them in the garbage. Pruning and training for better airflow can also reduce the time needed for blossoms to dry.

Scalybutt is a disease of citrus tree bark. Also known as exocortis, scalybutt is a virus-like disease caused by a particle, not a virus, called the Citrus exocortis viroid (CEVd).


Viroids are the smallest known infectious pathogens, made of a single, naked RNA strand. Other diseases caused by viroids include potato tuber spindle disease, avocado sunblotch, and peach latent mosaic.


Scalybutt used to be a serious threat to citrus trees, especially those grown with Trifoliate rootstocks, but strict regulations and agricultural inspections have reduced the likelihood of scalybutt affecting your citrus trees. That is if your trees are relatively young. Older trees (>40 years) may still be infected. This is important because you don’t want to spread exocortis viroids to uninfected trees.


Symptoms of scalybutt

If you see drying, cracking, and lifting bark, it may be scalybutt. Damaged bark may also peel away from the tree trunk in thin strips in a behavior called shelling. Of course, these are the same symptoms of sunburn damage, so how would a gardener know the difference? For one thing, you may also see gum droplets under the loose bark or stunting. Stunting occurs because nutrients have difficulty moving through damaged or exposed vascular bundles. Sunburn damage generally does not cause stunting or gummosis.


Dealing with scalybutt

You can’t cure scalybutt, and it is highly contagious. But it probably won’t kill your tree. It will reduce harvests and make the tree susceptible to other pests and diseases. Unless you are ready to commit to complete sanitation of shoes, tools, and anything else that might come into contact with an infected tree, its removal is your best option, if only to protect neighboring trees.

Imagine a container plant that grows a lush 6 feet tall and produces delicious, soft-skinned, seedless tropical fruits. Introducing… the babaco tree.


Also known as mountain papaya, babaco is cousin to that other sweet tropical fruit of mammoth size. Commonly eaten fresh, or used in fruit salads, smoothies, and ice cream, babaco (Carica pentagona Heilborn) is believed to be a naturally occurring hybrid from Ecuador. People have been eating babaco fruit since the 1500s, but I had never heard of it until recently.

For the best fruit production, prune out any additional trunks as soon as they appear, except for one trunk, sometime around September, every year or two. This new trunk will replace the existing trunk. Trunks are only productive for a year or two. Babaco can also be propagated from cuttings, but with less success.


Babaco grows best in light, well-drained soil. They require frequent irrigation and nitrogen feeding during fruit production. Mulching with composted chicken bedding will help your babaco tree thrive.


Pests and diseases of babaco

Babaco leaves are susceptible to fungal diseases, such as powdery mildew. Phytophthora root rot can also become a problem. Certain mites, specifically the two spotted mite and the strawberry mite can become problematic, as can snails and slugs, and deer.


Add a touch of the tropics to your home or patio with a delicious babaco!

Native to South Asia, mangos (Mangifera indica) were part of the spice trade of the 15th and 16th centuries. They were brought to the colonies in the 17th century but, because refrigeration was unavailable, those mangos were pickled. Due to poor communication, other pickled foods, such as sweet peppers, were also referred to as mangos. For a time, the word mango was a verb that meant “to pickle”. But I digress.


Types of mangos

You may be surprised to learn that there are over 500 mango cultivars. In commercial mango orchards, these cultivars are often interplanted to improve pollination. The current market leader is the ‘Tommy Atkins’ variety, due to its nice appearance, productivity, disease resistance, and shelf life. Other, less resilient cultivars, such as ‘Alphonso’, are said to provide better eating enjoyment. With so many cultivars to choose from, home growers can afford to be picky. And those mangos you buy in the store? Many of them (like many other fruits) are picked unripe, so they will never attain the rich flavor of a tree-ripened mango. These climatic fruits do continue ripening after leaving the parent plant, but their flavor is never quite what it could have been. [Keep in mind, when you buy mangos at the store, each fruit is picked by hand, then washed, polished, and stickered by people working in warehouses.]


The mango tree

Mangos are stone fruits, right along with apricots and cherries. And that large flat seed - it’s a drupe. Like legumes, pineapple, sorghum, and sweet potatoes, mangos have evolved alongside a helpful bacteria (Gluconacetobacter diazotrophicus) that fixes atmospheric nitrogen, making it available to to the plant and its neighbors, until it goes to seed.

Mangos are evergreen trees with large, broad leaves that start out orangish-pink, and then turn dark shiny red before maturing to dark green. Mangos produce small, white, fragrant flowers in clusters, called panicles. These flowers are pollinated by insects, but it is estimated that less than 1% of the flowers produced by a mango tree will every mature to form a fruit. It takes 4 to 5 months to go from flower to harvestable fruit. And you know that red blush on mango fruit? It has nothing to do with ripeness or sweetness. Instead, it is an indicator of how much sun that side of the fruit was exposed to as it grew.


Inside that delicious fruit is a drupe that fights being removed with every fiber of its being. The reason for this is because mangos, along with avocados, lychees, and cocoa seeds cannot tolerate being dried out or too cold. This type of seed is called recalcitrant. Recalcitrant seeds, also known as unorthodox seeds, lose their viability when stored. Other orthodox seeds can tolerate varying degrees of cold, dryness, and storage time. [Note, the stories about seeds from King Tut’s tomb germinating are bogus.] If you want to grow a mango tree from a pit, your odds will improve significantly if you start it right away. Most commercially grown mango cultivars and bare root stock are grafted onto sturdy rootstock.


​Before you start growing your own mango tree, you may want to find out if you are sensitive to the oils found in mango stems, sap, and leaves. Some people are sensitive, while others can be severely allergic. Also, mango trees are killed by extended exposure to temperatures below 30°F. If your microclimate receives substantial frost, you may need to protect your tree in winter. If you enjoy snowy winters, you may want to try growing a dwarf mango indoors and pollinating it by hand.


Commercially grown mango trees are often girdled by professionals to increase the sugar content of the fruit, but I advise against this practice, as it can kill your mango tree if done incorrectly.


Mango pests and diseases

Sadly, mango trees are susceptible to a wide variety of pests and diseases. This list is so long that I encourage you to skip it (unless you are really into this sort of thing). If you own a mango tree, you should familiarize yourself with each of these conditions and their treatments. 


According to Wikipedia, bacterial diseases of mango include bacterial fruit rot, crown gall, and bacterial canker. Fungal diseases of mango include alternaria leaf spot, anthracnose, black banded disease, black mildew, black mold rot, black rot, blossom blight, blue mold, branch canker, branch necrosis, ceratocystis wilt, charcoal fruit rot, charcoal root rot, crown rot, crusty leaf spot, curvularia blight, felt fungus, fruit rot, galls, gray leaf spot, hendersonia rot, leaf blight, leaf spot, macrophoma rot, fusarium dieback, mucor rot, mushroom root rot, phoma blight, phyllosticta leaf spot, pink disease, powdery mildew, Rhizopus soft rot, various root rots and seed rots, scab, sclerotinia rot, shoestring rot, sooty blotch, sooty molds, stem canker, stem end rot, stem gall, stemphylium rot, stigma leaf spot, tip dieback, transit rot, trunk rot, twig blight, verticillium wilt, white sooty blotch, wood rot, and various forms of dieback. Fixed copper sprays are the most common treatment for many of these fungal diseases.


If that weren’t enough, dagger, lance, and sheathed nematodes, vine mealybugs, guava fruit flies, Mexican fruit flies, melon flies, polyphagous shothole borers, and Oriental fruit flies will attack mango trees, as will an algae that causes red rust, along with a parasitic lichen. Copper, zinc, and boron deficiencies can also cause problems, while too much nitrogen combined with not enough calcium can cause a condition known as soft nose. It’s a wonder we get mangos at all!


Mangos, like most other tropical fruits, produce significant amounts of ethylene gas, a ripening agent. If you need to speed ripen an avocado for guacamole, put it in a paper bag with a mango.


Did you know that mangos are related to cashews?


Now you know.

Walnut trees, like citrus and many other fruit and nut trees, tend to produce heavy crops one year and a light crop the following year. Known as alternate bearing, these fluctuations allow trees to recover from heavy production years.


Toxic walnut

You have probably heard that walnut trees put out toxins that make it impossible to grow other plants nearby. This is only partly true. Many plants use a type of chemical warfare, called allelopathy, to reduce competition. Walnut trees produce do produce toxins that can cause some other plants to wilt. Tomatoes, potatoes, eggplant, peppers, blackberries, raspberries, blueberries, and asparagus do not grow well when planted near a black walnut tree, according to the University of Illinois Extension. At the same time, according to the PennState Extension, onions, beets, squash, melons, carrots, parsnips, beans, yarrow, stonecrops, and corn can all be grown near a walnut tree without any problems. In fact, in commercial walnut groves, a type of agroforestry, called alley cropping, is used to plant other crops, such as corn, between the rows of walnut trees.


Propagating walnut trees

While you can certainly buy a bare root walnut tree, there are other ways. You can plant a raw walnut in the ground, or, if you know of someone with a walnut tree, you can use air layering. Layering is a form of vegetative propagation. Strawberry runners are an example of layering. The nice thing about air layering is that the parent plant continues to feed and care for the newly developing plant, since they are still attached to one another. To air layer a walnut, pull a stem down until it touches the ground at what would have been a leaf node. Instead of developing into a leaf, that bud will start putting out roots.


Pruning walnut

Walnut trees can produce nuts on the same spurs for several years. Because of this, mature walnut trees do not require renewal pruning. The only pruning needed is occasionally thinning branches to maintain overall shape and good health. Young walnut trees are trained using the modified central leader system. In this method, a single, strong shoot is encouraged up the central line of the tree. Two or three lateral branches, spread evenly around the tree, both vertically and horizontally, are allowed to grow. All other branches are removed. Eventually, there can be five to seven lateral branches in place before the central leader is removed.


Walnut pests and diseases

Walnuts are susceptible to an astounding number of pests and diseases. Luckily, walnuts are rugged trees that rarely need assistance in fighting off these foes. It’s still a good idea to know what your tree might be up against. Many varieties of scale insects, including walnut scale, frosted scale, European fruit lecanium scale, San Jose scale, Kuno scale, and Italian pear scale may be found on walnut. Walnut husk flies, aphids, southern fire ants, walnut twig beetles, fall webworms, Pacific flathead borers, navel orangeworms, false chinch bugs, redhumped caterpillars, American plum borers, and Mediterranean fruit flies prefer walnut, as do tortricid moths, such as the light brown apple moth, which can cause leaf roll of walnut. A type of eriophyid mite, called the blister mite, will also attack walnut trees, as will European red mites and webspinning spider mites. Codling moth larvae will burrow into the nut meat of English walnuts, starting in April. You can monitor your trees for many of these pests by using pheromone traps.


Diseases, such as crown gall and walnut blight can be prevented and treated with Bordeaux mixture or fixed copper. Walnut trees may also become infected with anthracnose, armillaria root rot, phytophthora root and crown rot, branch wilt, and several canker diseases. If that weren’t trouble enough, squirrels, voles, pocket gophers, rats, and deer will try to get at as much of your walnut crop as they can.


While many trees are treated with horticultural oils during dormancy, oils should not be used on walnut. Dormant oils are phytotoxic (poisonous) to walnut trees. Like apricot trees, walnut trees are also susceptible to Eutypa dieback. This fungal disease can kill a tree. The easiest way to avoid it is to only prune your walnut tree during summer, when there are no rains expected. Also, make sure that your sprinklers are not hitting the tree’s trunk.


Walnuts contain high levels of oils that can turn rancid. To keep walnut meats fresh, they are left in their shells and placed in cold storage. If you buy walnuts from a store and plan on using them within one month, store them in your refrigerator. Since walnuts can absorb odors, be sure to keep them away from fragrant foods, such as cabbage, broccoli, and fish. Longer storage should be done in the freezer.


Walnut trees can make a magnificent addition to your foodscape, providing decades of delicious nuts and welcoming shade from the summer sun.

European and American chestnuts tend to grow more tree-like, with a single erect trunk, while the Asian varieties tend to be multilayered and more spread out. Also, the former varieties offer stunning fall foliage. There are hundreds of chestnut varieties to choose from. UC Davis offers an excellent list of chestnut trees suitable for growing in California.


Chestnut flowers

Like avocados, chestnuts have both male and female flowers. Chestnuts are not self-compatible, which means you will need at least two trees or shrubs to produce fruit. Flowers appear in late spring and early summer. Male (staminate) flowers are shaped like a cat’s tail and are called catkins. Catkins mature before the female flowers, and the pollen has a rich, sweet aroma. The female, fruit-producing (pistillate) flowers grow together in groups of 2 or 3, which end up forming a prickly, 4-lobed structure called a calybium. The calybium is what ultimately develops into the hull that protects the fruit. Pollen is moved predominantly by wind, though beneficial insects also perform some pollination.​​

Chestnut fruit

The fruit of chestnut trees is held in sharp, pokey burrs, called cupules. These burrs tend to be clustered. The burrs of some varieties each contain one nut, while other varieties can hold up to severn. Burrs turn yellowish-brown and split open as the fruit matures. Each fruit has a pointed end, called a flame, and an attachment scar end, called the hilum. Chestnut fruit has two skins: the hard outer pericarpus, called the heel, and an attached, thinner skin, called the pellicle or episperm. Chestnuts are both culinary and botanical nuts, unlike almonds, peanuts, cashews, and walnuts.

​
Chestnut lumber

Chestnut lumber is lovely, but larger pieces tend to split. Most chestnut lumber is now produced through coppicing. Young chestnut lumber is more durable than oak of the same age. Both species contain high levels of tannins. Chestnut wood was a common source of natural tannins for tanning leather.

How to grow chestnuts

Chestnuts are in high demand and the supply is limited. This keeps prices high, and is a good argument for growing your own (assuming you are not in a hurry). Going from bare root sapling to mature, productive tree takes about 10 years. Chestnuts need specific chilling hours to produce flowers and fruit. If the dormant period does not get cold enough, you will still have a beautiful tree, but no homegrown chestnuts. Also, if two chestnut trees are planted such that their canopies touch, they produce no fruit. We don’t know why.


Allowed to fall to the ground, chestnut seeds germinate right away. You can start them in a cold frame, container, or seedbed outdoors, where they will experience winter temperatures. Seedlings require protection from squirrels and other rodents.


Chestnut trees prefer full sun. They need good drainage and regular irrigation (31 inches per year). Once established, chestnuts are drought resistant. They do not grow well in heavy clay or alkaline soil. Chestnuts prefer a soil pH of 5.5 to 6.0. If you live in the Bay Area, where alkaline clay is pretty much the rule, don’t despair. Chestnut scions can be grafted onto oak rootstock! Chestnut trees are managed much the way walnut trees are grown. Chestnut trees should be trained into a modified central leader scaffold system for the best sun exposure and overall health.


Chestnut pests and diseases

Squirrels, rabbits, deer, wild boar, livestock, and birds can all take a bite out of your chestnut harvest. You may want to consider a tree cage, at least while the tree is small. Chestnut gall wasps (in southeastern states), some moths, the oak roller weevil, oak aphid, filbert worm, oak leaf mining moth, shot hole borers, and the chestnut weevil are common pests of chestnut, depending on where you live.


In 1904, some Asian chestnut trees that had been planted on Long Island, were found to be infected with chestnut blight (Cryphonectria parasitica, formerly Eudothia parasitica). Over the next 40 years, 4 billion chestnut trees died, nearly wiping out the American chestnut. Reforestation efforts, started in the 1930s, using seeds from the few remaining living stumps are giving this majestic tree a new lease on life, but it’s a slow process. There are now blight-resistant cultivars. Chestnut trees are also susceptible to Armillaria rot. On the other hand, chestnuts are believed to be naturally resistant to oak rot fungus. You can protect your chestnut tree against sunburn by whitewashing the trunk, and help it stay healthy by mulching under the canopy (but not touching the trunk).


Roasting chestnuts

Chestnuts have been candied, soaked in wine, and roasted as a holiday tradition throughout Europe for a very long time. To early Christians, chestnuts symbolized chastity, while in modern day Japan, they symbolize both good times (mastery) and bad times (strength).


You can roast your own chestnuts at home in the oven. Start with raw, unpeeled, chestnuts. Cut an X on the rounded bottom of each nut. Some people soak their chestnuts in water for 30 to 60 minutes before baking, others use wine, and still others don’t soak at all. You decide. If you do soak them in water, drain and pat dry before roasting.


Spread the nuts out on a baking sheet. Bake for at least 15 to 20 minutes, or until the skins have pulled away from the cuts and the nutmeats have softened. Take them out of the oven and let the nuts rest for a few minutes. Peel and eat!


Did you know that chestnuts are the only nuts that contain vitamin C?


Now you know.

​Types of guava

There are many varieties and cultivars of guava. You may have heard of apple guava, strawberry guava, and pineapple guava. While the first two are actually guava varieties, pineapple guava is a different species altogether. In the world of guavas, plants are sorted by fruit skin and flesh color, skin thickness, and sweetness. To find the best variety for your microclimate, contact your local County Extension Office.

Guavas are extremely drought tolerant, but plants require up to 39 inches of water each year to produce a good crop. Feeding roots only go down 9 inches, so top dressing with aged compost is an excellent way to keep guava trees fed.

​
Guava pests and disease

Guava wood is naturally resistant to insects and fungal disease. They are, however, susceptible to attack by weevils, mites, and guava fruit flies, and they are a host to the Caribbean fruit fly. Many moth and butterfly caterpillars will also feed on guava leaves, and the Erwinia psidii bacteria can cause rot diseases.


Guavas contain a lot of pectin, so it is easy to make guava jams, jellies, and marmalades.

Fresh, sweet cherries are delicious, but cherry trees can be difficult to grow.


According to UC California Backyard Orchard, “cherries are the most difficult trees to keep alive.” If you are still determined, let’s see what we can learn about these trees.


People have been enjoying cherries since prehistoric times. Cherries are stone fruits, which means the fruit is a drupe. There are two types of cherry trees: sweet (Prunus avium) and sour (Prunus cerasus). The two cannot cross-pollinate with each other. Both types are native to Europe and western Asia. Sweet cherries are also known as wild cherries or gean.

Plums, nectarines, apricots, cherries, peaches, and almonds are all stone fruits. But, so are olives, coconuts, mangoes, pistachios, and black pepper! So what, exactly, are stone fruits?

Prunus plants

The Prunus genus is part of the rose family, making plums, almonds, and all the rest distant cousins to loquats and soapnut trees. [Did you know that almonds, nectarines, and peaches are the same species? I didn’t either.] There are both edible and ornamental stone fruits. Hawthorn, flowering cherries, and cherry laurels are ornamental stone fruits, but I much prefer investing time, water, and garden space on plants that produce food. When that food happens to be summer sweet peaches and apricots, well, all the better! The fruit of Prunus can be loosely or firmly attached to the seed, hence the terms freestone or cling varieties. Most stone fruits contain compounds which, when chewed up, generate hydrogen cyanide, but don’t let that scare you off. This is mostly true of the seeds, not the fruit, and the amounts are too small to do anything but fuel sensationalists.


Propagating Prunus

If you plant the pit from a grocery store stone fruit, you probably won’t get offspring that looks, behaves, or tastes the way the first fruit did. This is because most bare root fruit and nut trees available today are a hardy rootstock grafted onto a productive, flavorful fruit producer. Many of these plants are propagated by twig scions and cuttings taken from adventitious roots, to create clones. Because all of these fruit trees are members of the same genus, they can be grafted onto one another and produce edible fruit. One variety of grafted tree, in particular, boasts 40 different types of stone fruit on the same tree! These botanical masterpieces are created by New York artist Sam Van Aken. He calls them Tree of 40 Fruit. You can find similar stone fruit trees, with 4 or 5 types of fruit, available in garden centers and catalogs. These are a great way to make use of a small space.


How stone fruits grow

Members of the Prunus genus are all perennial trees and shrubs descended from a Eurasian ancestor. As such, these trees are best suited to northern temperate regions, or climates with four seasons. If you want grow these productive, rewarding trees, be sure to select a variety that has a chilling hour requirement that matches your microclimate, otherwise, you might not get any fruit. Adding a stone fruit tree to your landscape is a lovely way to enjoy spring blossoms and summer fruit. There are many dwarf and semi-dwarf varieties that don’t take up a lot of room, and some can even be grown in large containers.


Caring for stone fruits

When you first get a bare root tree, you will need to select a site with lots of sunlight and good drainage. Dig a hole slightly wider than the spread out roots and as deep as the roots go. There is no need to dig any deeper or wider. If your soil is heavy clay, be sure to rough up the edges of the hole a bit, to make it easier for young roots to penetrate. Cover the roots with soil, making sure that the soil level is exactly the same as it was before, relative to the tree’s trunk. Covering the graft area or trunk with soil can lead to rot and death of the tree. Water it in well, gently tamping down the soil to remove large air pockets that would allow the roots to dry out.


It is a good idea to provide a tree support for your young tree. The first year or two, you can improve long term production by removing spring blossoms. This frees the young tree to focus its resources on developing a strong root system. As the tree becomes better established, it is still a good idea to thin fruit for better size and flavor.


Whitewash the trunk and exposed branches each spring with one part white, interior latex paint and one part water to prevent sunburn damage. Each spring and summer, stone fruit trees should be fertilized and irrigated properly, depending on the species, tree size and condition, and local weather.

Most stone fruits are deciduous, which makes tree training and winter pruning much easier. The only exception is apricot trees, which should be pruned in summer, due to the threat of Eutypa dieback. It is not unusual for a protective gummy sap to appear at pruning cuts and other wound sites. While these trees are dormant in winter, they are sprayed with dormant oil, to break the disease triangle of many common pathogens.


Corking (dried out fruit) can be prevented by making sure that the soil contains enough boron and calcium. Before adding soil amendments, be sure to get a soil test from a local, reputable lab. Over-the-counter kits are not yet effective enough to be useful. Properly maintained, Prunus trees are classified as low flammability plants, making them a fire safe addition to your landscape.


Pests and diseases of stone fruits

While each species has its own set of problems, most stone fruits must deal with attacks by aphids, mites, caterpillars, shot hole borers, glassy-winged sharpshooters, San Jose scale, Eutypa dieback, peach twig borers, naval orangeworms, mealybugs, and cucumber beetles. Diseases of stone fruits include cane blight, shot hole fungus, crown gall, brown rot, bacterial spot, peach leaf curl, and bacteria blast. Stone fruit trees use idioblasts to protect themselves, and you can apply fixed copper, sulfur, or Bordeaux mixture (Bt), each in their own way and time, to aid in protecting your stone fruit trees. [Never use sulfur on apricots.] Netting and tree cages can help protect the fruit from birds and squirrels, and sticky barriers are an excellent way to thwart crawling insects.

Almond leaf scorch is caused by the same bacteria (Xylella fastidiosa) that causes Pierce’s disease, in grapevines, and alfalfa dwarf disease. This disease can also infect many common weeds, including annual bluegrass, burclover, cheeseweed, chickweed, filaree, London rocket, and shepherd’s purse. This pathogen is found on many familiar plants, such as bermudagrass, blackberries, elderberries, fescue grasses, nettle, and rye, without causing any problems for the host plants.


How almond leaf scorch spreads

This disease is carried by sap-sucking insects, such as leafhoppers, sharpshooters, and spittlebugs. As they feed, the bacteria moves from the insect into the plant’s xylem, where it begins to reproduce.


​Almond leaves are normally a lovely green color. Around June, however, you may notice the edges (margins) of leaves look scorched. If you look closely, you will see a yellow band between the scorched portion and healthy leaf tissue. This scorched appearance looks a lot like salt burn, but salt burn lacks the yellow band.


This disease is normally seen on one branch, or one scaffold of branches. Scaffolds are major horizontal branches. Over time, this disease spreads to the rest of the tree. Another name for almond leaf scorch is golden death. While infected trees can live for several years, they will leaf out later and be far less productive than a healthy tree.


Leaf scorch management

If your beloved almond tree becomes infected, early detection is critical. The infected branch, or its scaffold, should be removed 5 to 10 FEET below any visible symptoms. Keep a close watch to see if any signs of infection appear elsewhere on the tree. If the tree is less than 10 years old, your best bet is simply to replace the tree.


I hope that your almond tree never faces this problem, but now you know what to watch for.

Nectarines are delicious fresh, stewed, baked, and sautéed. They freeze well and make excellent jam. Nectarines (and peaches) are so useful and tasty, that they have been cultivated for thousands of years. First grown in China, nectarines and peaches have been around for 2.6 million years!


What’s the difference between nectarines and peaches?

Fur. The only difference between a nectarine and a peach is a single gene that produces fuzzy skin (dominant) or smooth skin (recessive). A nectarine (Prunus persica var. nucipersica or var. nectarina) is simply a peach without the furry skin (trichomes). Nectarines and peaches are both members of the rose family, along with apples, pears, blackberries, raspberries, and strawberries. Nectarines and peaches, like apricots, cherries, plums, and almonds, are stone fruits. There are both cling and freestone varieties, and you can find yellow and white peaches and nectarines. [Yellow fruits are more acidic than white fruits.] Peaches and nectarines are also in a group of plants that use specialized cells for storage, manufacturing, and as weapons. These cells are called idioblasts. Don’t worry, though, they can’t hurt you.

Nectarine characteristics

The main reason you do not see nectarines in the store year round is because they do not ship and store well. While nectarines are usually smaller, firmer, and more aromatic than peaches, they also bruise more easily. [All the more reason to grow your own!] A standard nectarine tree can reach over 30 feet in height, semi-dwarf varieties reach 12 to 15 feet tall and wide, while dwarf nectarine trees are only 8 to 10 feet and they can be pruned for an even smaller size while still producing a good crop. Nectarines can also be espaliered, if you only have a narrow space along a wall or fence.


Each spring, your nectarine tree will produce lovely pink blossoms, followed by a delicious crop of fruit, and then all the leaves fall off (making dormant pruning so much easier!). Before you jump on the nectarine bandwagon, however, that yummy fruit can only occur if enough chill hours are accumulated each winter.


Nectarines and chill hours

Chill hours are an accumulation of temperatures between 32°F and 45°F. Somehow, trees keep track of this information. I have no idea how. If enough chill hours are not accumulated, nectarine flowers and buds will not form properly, which means you might not get any fruit. Different nectarine varieties have different chill hour requirements, so it is important that you select a variety appropriate to your location. Do not trust your local box store to sell you the right one. Most nectarine trees need 650 to 850 chill hours. Here in the Bay Area, we only get 450 chill hours (or 52 chill portions). You can learn your own chill hours on my chilling hours page.


Nectarine site selection

Once you have found a variety that matches your garden’s chill hours and your personal tastes, you will want to select a site with excellent drainage and plenty of sunshine. Also, nectarines prefer a soil pH of 6.5. Here, in the Bay Area, our soil is more alkaline than that, so acidification may be needed for the best results. Nectarines, like peaches, are self-fruiting, so you do not need multiple trees for pollination. While you may be tempted to grow a nectarine tree from a pit, think twice about that. Most commercially grown nectarines are actually from two different trees: a root stock and a fruit producing tree. These two trees are grafted together to take advantage of the benefits provided by a strong root system and good fruit production. Your store bought nectarine pit may never produce fruit at all. Or it might. You are far better off buying bare root stock from a reputable producer. Nectarine trees can also be started from twig cuttings called scions.


How to plant a nectarine tree

Bare root trees are best planted in winter and early spring. Examine the root system for signs of disease or damage. These bits should be cut out. If your bare root tree is not going to be planted right away, it should be soaked in a bucket of water for 6 to 12 hours, but no longer. [Plants can drown, too, you know!] When you are ready to plant, dig a hole that allows the roots to spread out freely. If the soil is heavy clay, be sure to rough up the edges of the planting hole. Containerized and balled trees should be given a hole slightly larger and the same depth as the container or root ball. In any case, it is very important that the soil level remains the same. Add soil around the roots and water thoroughly. This removes air pockets that can dry roots out before they ever get a chance to grow. Mulch around your new tree and water regularly until the root system has become established. The first 2 or 3 years, flowers should be removed, to encourage a strong root system. I know it’s hard, but you’ll thank me later.


Feeding and watering nectarines

Nectarine trees use a lot more nitrogen than other fruit and nut trees. You can use blood meal, ammonium sulfate, or commercial 10-10-10 fertilizer to feed your nectarine tree. Young trees will need a total of 10 to 15 lbs. of manure or 1/4 lb. of urea, spread out over the months of spring and summer. Mature trees should receive twice that amount. If your nectarine tree doesn’t get enough nitrogen, you will start seeing red areas on the leaves.


Nectarines are shallow-rooted trees, so they are susceptible to water stress during the summer. You can protect your tree with deep irrigation and a thick layer of mulch, just make sure that the mulch does not actually touch the tree trunk. If your nectarine tree becomes too water stressed, it will develop a condition called bitter fruit which is exactly how it sounds. The problem is, once bitter fruit occurs, the tree will forever after produce fruit that is bitter. If you keep your nectarine tree properly irrigated throughout the growing season, you can improve the taste and sweetness of the fruit with deficit irrigation, just before harvest.


Another technique used to improve both the quantity and quality of fruit is called cincturing, or scaffold girdling. This is not the same thing as girdling your nectarine tree with the weedwacker. Get help from an experienced arborist, rather than trying this on your own, as it can kill your nectarine tree.


Nectarine pruning and thinning

Nectarine trees perform best when they are trained in what’s called an open center system. This is exactly what it sounds like. Each winter, you will want to remove 50% of the previous year’s new growth. This will stimulate fruit production and maintain a reasonable tree size. One problem that commonly occurs with nectarines and peaches is that trees produce more fruit than they can support. This can mean broken branches. Proper pruning and fruit thinning can save your tree. Thin fruits to 6 inches apart when they are the size of a marble. If you think there is too much fruit on a branch, you can always prop it up with a board or other support until after the fruit is harvested, and then prune and thin more heavily next year.


​Nectarine pests and diseases

The most common diseases faced by nectarine trees here, in San Jose, California, are peach leaf curl and brown rot. Nectarine are also susceptible to crown gall, bacterial blight, citrus blast, bacterial spot, stem blight, and shot hole disease.

Peach twig borers are a common pest of nectarines. Peach twig borer infestations often appear as dead twigs, called flags or shoot strikes. Luckily, many beneficial insects, such as braconid wasps, mealybug destroyers, and tachinid flies love to eat peach twig borers, so avoid using broad spectrum pesticides. Armyworms, earwigs, eugenia psyllid, Japanese beetles, mealybugs, San Jose scale, green fruit beetles, Mediterranean fruit fly, armored scale, eriophyid mites, katydids, and birds are also common pests. [Who can blame them?] You can use tree cages to protect your crop from birds in summer. Kaolin clay can be applied to individual fruits to protect against some pests.


In fall, after harvesting your delicious crop and before the first heavy rain, apply fixed copper to control shot hole fungus, fertilize plants one last time, and give your tree a deep watering. After all the leaves fall, move them away from your nectarine tree. Destroy or compost the leaves to prevent the spread of apple scab. As always, remove mummies as soon as they are seen.


Bordeaux mixture, dormant oil sprays, and fixed copper sprays should be used in fall and winter to protect against San Jose scale, shot hole disease, and other fungal diseases. You can prevent brown rot with a spring fungicide application. Crawling pests can be blocking from reaching fruit by wrapping the tree trunk with a sticky barrier.

The “Y” system
​
The “Y” system features two scaffolding branches, heading in opposite directions, creating a “Y” shape. Look at it as a two-dimensional open center style. This method is particularly good for peaches and nectarines. It can also be used for apples, plums, cherries, and pears.


Espalier

Espalier training is a trellising system used to create a two dimensional shape. This method works well alongside driveways, paths, buildings, and fences.


If you end up removing smaller, new wood, you can save these and use them as scions, to create new trees or modify existing trees. They make good gifts for fellow gardeners, as well!


Also, as you work closely with your tree, keep a look out for scale and other insect pests that may be overwintering in your tree’s bark.

Peaches may be the last thing on your mind right now, but autumn is a good time of year to find room on your property for a peach tree. Even if you don’t have room in your yard, dwarf peach varieties can be grown in containers.


Peach trees make a lovely addition to a foodscape. Fragrant spring blossoms give way to fruit that practically defines summer. Autumn leaf drop makes pruning easy and what winter would be complete without a surprise dessert of peach cobbler? A mature peach tree can produce up to 65 pounds of fruit each year. That’s over 200 peaches!

History of the peach

Did you know that peach trees have been around for over 2.6 million years? Traditionally thought to be from Persia, genetic research shows that peaches actually originated in China. Also, it was thought that peach cultivation started some 6,000 years ago, until some ancient writings showed that certain kings and emperors, back in the 10th century B.C., favored a delectable peach now and then. So, if you love peaches, you are in good company.


The peach tree

Peaches and nectarines are the same fruit, like fraternal twins. The only difference is that peaches have fuzzy skin (trichomes) and nectarines are smooth skinned. This difference is due to a recessive gene, the same way blue eyes or red hair occurs. Peaches are in the rose family, members of the Prunus genus, all of which produce fruits called drupes. This makes them cousin to almonds, apricots, cherries, and plums. Peach trees are in a group of plants that use specialized cells for storage, manufacturing, and as weapons. These cells are called idioblasts.


Standard peach trees can grow 25 to 33 feet tall and 25 feet wide, if you let them. For the best productivity and tree health, it is better to keep them pruned to 15 feet by 15 feet. Dwarfs can reach 8 to 10 feet. Most peach trees in Maine only live 7 years, while California peach trees live 12 to 20 years.


Peach trees and chill hours

Before you plant a peach tree, you need to understand chill hours. Each winter, peach trees enter a period of dormancy. Being deciduous, they lose all their leaves and enter a winter rest. During that rest, the number of hours spent between 32°F and 45°F are accumulated (don’t ask me how - I have no idea). These “chill hours” must reach a certain number for a tree to be able to blossom properly in the spring. Once enough chill hours are accumulated, the tree enters a different type of dormancy called quiescence. Depending on the variety, peach trees need 600 to 900 chill hours. Here in the Bay Area, we generally only get 450 chill hours. When selecting a peach tree variety, you want to take chill hours into account. There are several models used to calculate chill hours, and each one gives you different information. Below you can see the chill hour results for the South Bay Area. Go to my page on chilling hours to learn how to get your local information. There are hundreds of varieties to choose from. According to UC Davis, using the Dynamic Model, the following varieties have their chill hours noted alongside:

[Using the Dynamic Model, San Jose receives an average of 52 chill portions each year, so only two varieties would be a good choice.] You can see detailed list of different fruit trees at the UC Davis Home Orchard.

Peach varieties

Peach varieties are divided between cling and freestone. Those names refer to how easily the fruit comes away from the pit. Freestone peaches tend to have firmer fruit, while clingstone peaches are known for their sweeter taste. Clingstone varieties are harvested May through August, while the freestone harvest extends into October. There is also a hybrid cross between the two, called a semi-freestone, and flat varieties, called pan-tao. Not all peach tree varieties perform well in all regions or microclimates. Check with your local County Extension Office and be sure to verify your growing zone using the USDA Hardiness Zone Map.


Growing a tree from a peach pit

While you can eat a peach and then plant its seed, this doesn’t always work out the way you expect. Like apples and many other fruits, peach seeds do not necessarily produce offspring that taste as good or grow as well as the stock you buy at your local nursery. This is because most fruit and nut trees are grafted. Grafted trees have an aboveground part from one variety and a root stock from another variety. This is done to take advantage of one variety’s ability to develop strong roots, while other varieties may taste better or be more pest or disease resistant. Also, your pit grown peach tree will not produce fruit for a few years, and some will never produce fruit.


If you want to give it a try, you can simply put your peach pit in the ground and let nature take its course, or you can refrigerate the pit until December or January. This method, called stratification, fools the pit into triggering winter processes (vernalization), in preparation for spring. Just soak your pits in water for a couple of hours, and then place them in a plastic bag, along with a little moist soil. This bag goes into the refrigerator, until you see signs of germination. This can take a few weeks or months, depending on the variety and other factors. Since peaches emit high levels of ethylene gas (a ripening agent), you should keep them away from other fruits and vegetables. Once it starts germinating, remove it from its cold environment and let the planting begin! But first, you need to select the best location for your peach tree.


Peach tree site selection

Peach trees need plenty of sunshine, but they will also benefit from a little protection at the extreme points of summer and winter, if possible. Being susceptible to several fungal diseases, peach trees also need good drainage. Peach trees prefer a soil pH of 6.5. Here, in the Bay Area, we tend to have more alkaline soil, so acidification may help your tree thrive. Of course, you won’t know what your soil is without a test from a reputable lab. Just sayin’…


How to plant a peach tree

Bare root trees are best planted in January and February. Your peach sapling should be planted right away, or soaked in water for 6 to 12 hours before planting. If you have a bare root tree, gently spread the roots out to see how much space they can use and dig a hole that will accommodate them. This is also a good time to clip off any dead, diseased, or damaged roots. Be sure to rough up the edges of your planting hole. If you don’t, the smooth clay left by your shovel can create a tough barrier for young roots. Containerized and balled trees should be given a hole slightly larger and the same depth as the container or root ball. It is very important that the soil level remains the same. Add soil around the roots and gently tamp it down. This removes air pockets that can dry roots out before they ever get a chance to grow. Mulch around your new tree and water it in well. Peach trees can also be started from twig cuttings called scions.


Peach tree care

Peaches are self-pollinating, which means that another tree is not needed to produce a crop. If you have room for more than one tree, be sure to space them 12 by 16 to 18 by 18 feet apart. Peaches perform best when trained with what’s called the “Y” system. The “Y” system features two scaffolding (main) branches, heading in opposite directions, creating a “Y” shape. You can picture it as a two-dimensional open center system, which also works with peaches. These tree training systems leave the trees open in the center, allowing lots of air and sunlight to reach the fruiting wood. Peaches can also be espaliered.


​Feeding and watering peaches

Peach trees use a lot of nitrogen. You can use blood meal, ammonium sulfate, or commercial 10-10-10 fertilizer to feed your peach tree. Nitrogen deficiencies in peach appear as red areas on the leaves. Peaches are shallow-rooted, so they are susceptible to water stress during the summer. Too much stress can lead to a condition called bitter fruit that can mean the end of the useful production of your tree, so irrigate accordingly. Near the end of fruit development, deficit irrigation can be used to improve taste and sweetness.


While you certainly want to avoid girdling your peach tree with the weedwacker, doing it on purpose, called cincturing, or scaffold girdling, can increase production and fruit quality. You just have to be really careful that you don’t kill your tree in the process.


Peach pests and diseases

Peaches are susceptible to these bacterial diseases: crown gall, bacterial blight, citrus blast, and bacterial spot. Fungal diseases include stem blight, peach leaf curl, shot hole disease, and brown rot. Armyworms, peach twig borers, earwigs, eugenia psyllid, Japanese beetles, mealybugs, San Jose scale, green fruit beetles, Mediterranean fruit flies, armored scale, eriophyid mites, katydids, and birds are the biggest pests. Luckily, beneficial insects, such as braconid wasps, mealybug destroyers, and tachinid flies love to eat peach twig borers!


Pheromone traps can be used to monitor many of these pests and sticky barriers will prevent many pests from ever reaching tender buds, shoots, and fruit. Bordeaux mixture, fixed copper, and dormant oil can be used to prevent or treat some bacterial diseases, fungal diseases, and pest infestations. Kaolin clay can also be used to prevent some pest damage. Since fruiting occurs from pollination by honey bees, flies, and other pollinators, avoid using broad spectrum pesticides. 


When to harvest peaches

Color and smell are good ripeness indicators, when it comes to peaches. Yellow skin, which may or may not have a red tinge, and that amazing sweet summer aroma of ripe peaches are reason enough to give one a try. Taste, ultimately, is the only true indicator of ripeness, but who can complain about conducting that test? If the fruit comes away from the stem easily, it is ripe.

Persian limes with brown bottoms have stylar end rot.


Also known as stylar end breakdown, stylar end rot primarily affects Bearss, Tahitian, and other Persian lime species but can occur in other lime and lemon varieties. Stylar end rot found on guava is a fungal disease.


Stylar end rot is a physiological disease caused by too much heat. Even though limes, lemons, and other citrus have thick, waxy skins to protect themselves from the sun’s heat and drought conditions, sometimes that protection isn’t enough.


Symptoms of stylar end rot

The stylar end of a fruit is the part with the dried-up petals. It is opposite the stem end. Stylar end rot starts as a small, grayish sunken area that slowly becomes firm and leathery. Some fungal diseases exhibit similar symptoms:

• Alternaria rot—fruit looks ripe when it isn’t; inside is rotted
• Anthracnose—soft, sunken brown areas with visible white fungal growth
• Brown rot—starts as stinky tan or olive brown lesions anywhere on the fruit
• Blue (green) mold—also known as clear rot; anywhere on the fruit

Affected areas can spread to cover 1/4 to 1/2 of the fruit. Bacteria and fungi often infect these compromised areas. The tissues inside break down and turn brown or pink. Diseased fruit can go in the compost pile, but only if it is free of other fungi and bacteria. Otherwise, toss it in the trash.


Preventing stylar end rot

You can’t. Stylar end rot occurs when vulnerable citrus fruits experience an accumulated 18 hours of temperatures over 105°F. Think of it as reverse chill hours. Pick the fruit earlier, after particularly hot summers, and hope for cooler weather next year.​