Click on a month to learn more about common Bay Area gardening chores.
With all the hustle and bustle of the holiday season, it is easy to put aside garden tasks for another time. We need to rest when we can, too, just as our garden plants do each winter. But December is an excellent time to prevent future problems in the landscape. With just a little bit of effort now, we can have bigger harvests and healthier plants next summer.
Bare root planting
December is an excellent time to install bare root plants in California and other warmer regions. Any of these bare root plants can be planted in December:
Occasional rains will help keep compost piles moist, but remember to turn your compost pile to incorporate the oxygen needed by helpful microorganisms. You may need to cover your compost pile during heavy rains to prevent losing all those valuable nutrients
You can protect your crops by using the USDA Hardiness Map to determine your planting zone and learning when to expect frost to occur. I’m in Zone 9b, which means my first and last frost dates are November 15 and March 15. For plants that may be damaged by frost, you can protect them by draping sheets, tarps, or other light fabric over and around them using poles and string. Do not allow the fabric to touch the plants. Umbrellas and old fashioned (not LED) Christmas lights can also provide some protection. Potted plants can be brought indoors or closer to protective structures. And be sure to water frost sensitive plants. Damp soil holds more heat than dry soil. Also, mulch can stabilize below ground temperatures. If frost damage does occur, resist the urge to clip away the damaged bits - they create a barrier against further frost damage. If it looks really hideous, leave it covered
Garden bed care
As many annuals end their lifecycle, be sure to remove them from the garden bed by cutting them off at soil level. This allows valuable soil microorganisms the time they need to migrate to another plant and the roots will add nutrients to the soil as they decompose. Adding aboveground plant debris to the compost pile not only creates nutrient-rich compost, but it interrupts the lifecycle of many garden pests and diseases. If plant materials are already diseased, they should be thrown in the trash.
Holiday plant care
Poinsettias, Christmas trees, Christmas cactus, amaryllis, and many other holiday plants find their way into our homes in December. Most of these plants prefer cooler temperatures and higher humidity than our homes can provide. Keeping plants away from heater vents and misting them occasionally will help. Also, avoid overwatering.
Winter irrigation is largely dependent on the weather. December is a good time to turn off the sprinklers and monitor the soil with a moisture meter. Cooler temperatures mean slower growth but some water is still needed. Also, if an area becomes saturated with water, avoid walking on it. This prevents soil compaction.
If a tree branch is torn by heavy winds, you can help it heal by cutting the wound to make it a flat surface, close to the trunk, but not cutting into the branch collar. You do not need to paint the wound. Instead, allow the tree to protect itself. It will grow a callus over the area. You may, later on, need to provide the callus with sunburn protection. These other tips will also help your trees stay healthy this winter:
With just a little care now, you can be sure your garden will get through winter for a better spring to come.
Happy holidays, fellow gardeners!
Potential for frost
Sudden rain and shorter days
Just as natural cycles cause plants, animals, and insects to draw closer to home, move around or grow less, and to retain resources, we can copy those behaviors to the benefit of our garden and landscape. While there is still time to plant spring blooming bulbs, winter crops mentioned in the October notes, and cover crops, November is an excellent time to clean up and prepare for the holidays and colder weather.
Fall clean up
If you haven’t already, this is a good time to discard any plants that are not thriving. Annuals and other garden plants that have completed their life cycle are best removed by cutting at ground level, rather than pulling. Pulling plants up by the roots disrupts microbe populations, which interferes with soil health. Also, by cutting plants off at root level, you may get a surprise next spring when that annual turns out to be more tenacious than you thought!
Before the rains get started, this is a good time to look through stacks of materials to see what needs cleaning, repairing, sharpening, or discarding. Plant saucers and pots should always be scrubbed clean and then soaked in a household cleaner, such as Lysol, for ten minutes to prevent the spread of disease. They should also be stored upside down or on their edge to prevent water collection and mosquito breeding. I used the staves from a half barrel that fell apart to create a simple storage system for planter saucers. I just drilled screws in from above. It makes them easy to see and they do not collect water. Garden tools should be cleaned, sharpened, and oiled before damp weather sets in.
As trees drop their leaves, think before you rake. Fallen leaves make excellent compost or mulch but they will interfere with your lawn, if you still have one. Leaves should be removed from lawns and concrete (due to staining), but there is no reason that I know of for removing leaves from anywhere else. From my point of view, fallen leaves are plant foods and soil amendments that have been around a lot longer than us. The only exception might be leaves that are exposed to a lot of car exhaust. You might not want to add those amendments to your soil. Also, really thick layers of leaves, more than a couple of inches, can interfere with soil respiration. If you have that many leaves, it is a good idea to chip them, or chop them with your lawnmower to speed decomposition up a little bit.
Sooty mold fungus
Remember those aphids, mealybugs, whitefly and scale bugs that tormented your garden all summer? Well, they left behind copious amounts of honeydew that create the perfect growth medium for mold. Sooty mold is common in San Jose, California, and is easy to recognize as black smudges on leaves and fruit. While the mold can be washed off food and eaten safely, it can be devastating to host plants. The mold actually blocks sunlight from entering the leaves, slowing or even halting photosynthesis. Ants carry the disease, so slowing ant traffic can be a big help. The easiest way to block ants is to wrap tape around the trunks of trees and apply sticky barriers to the tape. Also, trim branches away from buildings, fences and other plants, and use ant bait. While you are at it, November is also the perfect time to caulk your home against winter invaders.
Fires can be devastating. Dried brush, dead weeds, and stacked firewood can speed a fire closer to your home than anyone wants. Well-watered plants are less likely to catch fire. It is all too easy to think it won’t happen to you, but it can. Change the batteries in your smoke detector, have your chimney and/or furnace inspected, and look at your landscape with an eye for fire safe gardening.
Cooler temperatures may reduce the number of pests in your garden and landscape, but imported cabbageworms, brown marmorated stink bugs, and Harlequin bugs will be doing their very best to wreck your cole crops. Cabbages, cauliflower, and broccoli leaves should be checked frequently for imported cabbageworm butterfly eggs (tiny clear-ish white flecks on the underside of leaves), small (and some not-so small!) green cabbageworms, and clusters of drum-shaped Harlequin bug eggs. These eggs can simply be extermigated (brushed off) and the hatched larva will generally be unable to find their way back to the host plant. You can also use row covers, once you are absolutely certain that you have removed all the eggs. [Check every few days anyway, just in case.]
It may be difficult to imagine frost in California, but Santa Clara Valley's first frost date is November 15th. Frost dates are statistical averages over time. They are not written in stone. I can tell you, speaking from experience, it is far easier and more comfortable for you to prepare your plants' frost protection against winter sunscald and frost cracks before it is needed. Old bedsheets, row covers, and even umbrellas can provide all the protection that's needed, just be sure to make it so that the fabric does not actually touch the plant.
You can stabilize soil temperatures, reduce weeds, and slowly add nutrients to your soil with mulch. You can buy different sizes, colors, and materials, or you can contact local tree trimming companies for free mulch. Wherever it comes from, be sure that it is disease-free and that it won't float away when the rains comes.
Orange-red leaves fall
Torn from brittle stems, take flight
Soon for winter sleep
October is the perfect time to prepare for a lovely spring. This is the season for removing weeds, dead plants, and pest habitats. It is also the time to plant winter crops. Best of all, October is the perfect time to install your very own herb garden! Cooler temperatures and (hopefully) rain provide conditions needed for thriving winter vegetables, spring blossoms, and ongoing herbal culinary treats.
Bring out your dead!
Tomatoes, peppers, squash, and many other garden fruits and vegetables are now at or near the end of their productive lifecycle. While tomatoes are technically a perennial, most tomato plants are treated as annuals. Rather than pulling spent plants from the ground and destroying soil microbes, it is far better for soil health to cut the plant stems and stalks off at ground level. This allows roots to die off slowly, in the ground, providing soil microbes with the time they need to adjust. Next, inspect that plant debris closely for signs of diseases, such as bacterial spot. Infected plant material and mummies should be disposed of in the trash. Healthy plant material makes an excellent addition to the compost pile. Chop thick stalks into smaller pieces to improve your compost pile’s natural processes when adding last summer’s plant material to the pile.
Fall flower care
This is also the time to continue weeding and deadheading flowers. Removing blossoms properly allows flowering to continue for as long as temperatures allow. The only exception is roses. To encourage your rose bushes to enter a much-needed dormancy, it is better to start removing only the flower petals and leaving the rose hips attached to the stem. Be sure to dispose of seeded weeds, rather than adding them to your compost pile. If you are raising chickens, weeds with seeds make excellent forage.
Ensure the plants closest to your home are those that hold moisture. Succulents are a an example. Also, clear dead plant material and other burnables away from your home and other structures. Simply living in the suburbs is no guarantee against fire loss. Be sure to use fire safe gardening methods.
Prepare winter beds and protect the soil
Collect fallen leaves from under fruit and nut trees, rose bushes, rhododendrons, camellias, and azaleas to prevent the spread of pests and disease. Add them to your compost pile as long as they are pest and disease free, otherwise toss them in the trash. Pine, juniper, and oak do not need leaf litter removed. Add a thick layer of mulch or aged compost on top of all your planting beds. This will help prevent erosion and add nutrients to the soil for next year. Planting legumes, such as cowpeas or fava beans, can also add nitrogen to the soil, as long as they are not allowed to go to seed. Bare earth should be covered with a thick layer of wood chips, which you can get for free from local tree trimmers. Wood chips prevent erosion, add nutrients, and slightly acidify the soil. They look nice, too!
Spring bulbs & winter crops
Nothing says spring like brightly colored bulbs emerging from the barren muck of winter. Now is the time to shop for those spring bulbs and put them in the refrigerator (not the freezer) for 6-8 weeks. Use a paper or mesh bag to allow the bulbs to breath. You will want to keep them away from apples, which emit ethylene gas and will cause the bulbs to sprout too early. If you already have bulbs or perennial flowers, this is a good time to dig them up and divide them to allow for better growth in the spring. In San Jose, California, autumn is the perfect time to winter crops from these plant families:
• Allium - white, yellow and red onions, leeks, shallots, scallions and garlic
• Apiaceae - caraway, carrots, celery, fennel, lovage and parsley
• Brassicaceae - Bok choy, broccoli, Brussels sprouts, cabbage, cauliflower, radish, arugula, collards, kale, turnips, rutabagas, and kohlrabi
• Amaranthaceae - spinach, beets, and chard
• Asteraceae (the daisy family) - artichokes, lettuce [Surprised you, didn’t I?]
You can set the stage for a lovely spring by scattering native wildflower seeds in autumn. Here, in San Jose, our winter rains provide the moisture needed for these seeds to germinate and grow. As winter winds down and temperatures begin to rise, your wildflowers will put on a spectacular show of color. This is also a good time for installing shrubs and trees.
Create your very own herb garden!
You can create an herb garden in your yard, on a balcony, or even inside your home. The following herbs and spices can be planted now to provide years of delicious meals and lovely displays, wherever they are grown:
When spring comes around, you can add basil, anise, borage, oregano, lemongrass, marjoram, and sage to your herb garden for a tasteful gardening experience!
Which plants are you putting in this October?
Cooling, shorter days
Succulent harvest abounds
Prepare now for cold
Harvesting the fruits of all that labor and preparing for winter keep the September gardener busy. Deadheading, clearing away debris, and composting spent annuals all help to prevent future problems with pests and diseases.
Many apple varieties are ready for harvest (assuming the birds have left any uneaten). Other apple varieties will need some colder weather to sweeten. If you notice small brown, corky areas under the skin, it is called bitter pit. Bitter pit, like blossom end rot in tomatoes, is caused by a calcium deficiency early in the spring. In this case, however, the condition can be treated on future crops by spraying the leaves with calcium nitrate just after bloom and again one or two months later. Use one tablespoon per gallon of water.
Carrots prefer loose soil, but shorter varieties perform well enough in our heavy clay. The addition of compost can help aerate the soil and provide valuable nutrients. Carrots should be planted no more than 1/2” deep and plants should be thinned to 3” apart, to avoid forking and twisting. Water regularly but allow some drying to prevent cracking. Successive plantings provides an ongoing harvest. Carrots can be planted between landscape perennials for productive use of space.
Areas of the garden that will be left bare over the winter are better planted with cover crops. Cover crops help maintain important soil microorganisms that will, in turn, support your spring and summer crops next year. Fava beans are an excellent choice in the Bay Area.
If rose leaves are exhibiting neat round or oval holes in them, it is probably the beneficial leaf cutter bee and should be ignored. The sections of leaf are used to line brood cells, which are also filled with nectar and pollen.
Squash and cucumber plants are susceptible to a disease carried by aphids and cucumber beetles. Mosaic virus causes leaves to become mottled and stunts plant growth. Fruit may become white. Diseased plants should be removed and put in the trash. Do not add to the compost pile.
As nights become cooler, it is common for powdery mildew to strike. Affected leaves should be removed and thrown in the trash, and overhead watering should be avoided.
Gnawed fruit, empty snail shells, and tiny black pellets are all signs of roof rats. These pests can infiltrate your attic, crawl space, garage, storage shed, and trees. Rat traps are an excellent way to remove resident rats. Keeping pet and livestock food sealed up and harvesting crops as soon as possible will help make your yard less desirable to the local rat population. Since rats can carry serious diseases and damage electrical wiring, it is worth the effort to get rid of rats.
If leaf stippling and tiny webs are seen, spider mites are probably the reason. Spider mites prefer dusty conditions, so spraying infested plants with the hose can help. Using broad spectrum pesticides is not recommended because they will kill the spider mites’ natural predators. Heavy spider mite infestations can be treated with insecticidal soap or horticultural oil.
Any yellow flowers produced by your tomatoes now will not have time to mature before temperatures cause fruit to turn mealy before maturing. Instead, remove those flowers to encourage plants to put all their energy into any fruit that is already on the vine.
September is the time to plant many winter crops, including artichoke, arugula, beets, bok choy, cabbage, carrots, cauliflower, chard, cilantro, collards, dill, fennel, kale, leeks, parsnips, peas, radishes, rutabagas, spinach, and turnips.
Enjoy the fruits of your labor!
Foggy mornings pale
Seared from sight by blazing sun
Nectarine juice drips
Aside from watering, August may seem like the perfect time to take a break form the heat, but there are still plenty of things going on in your garden!
While ants do help aerate the soil, they can also damage crops and spread disease. Fruit trees can be protected with sticky barriers. Boric acid bait traps can be an effective control method, just be sure the baits are placed where children and pets cannot reach them.
Now is the time to be on the lookout for codling moth larva. From the outside, an apple will have a small, scabby spot. If you cut (or bite) into the apple, you will see that this spot leads to a trail that heads toward the core. You can interrupt the codling moth lifecycle by collecting and removing any fallen fruit that would provide an overwintering haven. Unaffected apples can also be protected by bagging them or dusting them with kaolin clay.
Unlike other trees, which are pruned when they are dormant, apricot trees are best pruned in summer. This is because apricot trees are susceptible to a fungus called Eutypa dieback, which can infect trees if rain reaches fresh pruning cuts.
This is the time of year when Japanese beetles, dried fruit beetles, and June beetles are the easiest to see (and eliminate). Japanese beetles will skeletonize many plants. These pests tend to cling to their favorite foods and are easy to knock into cans of soapy water. [When I lived in Virginia, I used to pay the neighborhood children a nickel for every June bug they eliminated - it was very effective and the kids had fun and earned some money!] June bugs are clumsy fliers and easy to slap down with a net. Most beetles can be fed to chickens. Dried fruit beetles and June bugs do not bite or sting and dogs can be trained to chase and kill them before they lay eggs in the soil. These eggs will later hatch and the larval grubs will devour lawn, ornamental, and other plant roots.
Just as in April and June, oranges and other mature citrus trees should be fed one-half pound of nitrogen in August. Blood meal is an excellent source of nitrogen, without all the fillers. Ammonium sulfate is another good source of nitrogen.
This is the time of year when all that hard work and patience really pay off. Keep plants healthy and enjoy the fruits of your labor by harvesting frequently. This reduces the number of places where pests and diseases can hide. This also prevents many plants from going to seed and ending fruit production. When harvesting tree fruit, be sure to keep a look out for mummified fruit. Remove mummies and dispose of them in the trash, not the compost pile.
This drought tolerant shrub is a great way to attract pollinators. After it has bloomed, cut lavender plants back, close to the ground. This will prevent plants from becoming too leggy and it stimulates more flower development.
If you have a lawn and it has not turned completely brown, allow it to grow longer than you would in cooler months. Taller grass protects and shades the soil and helps retain moisture. You can even let it go to seed and save money on lawn seed in the autumn! Be on the lookout for masked chafers and southern chinch bugs.
This has been a particularly bad year for mites in my garden. Mite infestations often look like nothing more than light webbing around leaves and stems. This webbing is followed by leaf stippling, chlorosis, and leaf drop. Water-stressed plants are more susceptible, as are dusty plants. Mites are related to spiders. Adults have eight legs, but the young only have six. Spraying pesticides often backfires because mite predators, such as lacewings and pirate bugs, are killed. Often, you can use a soft-bristled brush to dislodge these pests.
Moles and voles
Underground ridges in your lawn often mean you have moles. Moles eat insects and worms, but their tunneling can damage roots and redirect irrigation water away from your plants. Voles will devour root systems. In both cases, trapping is your best control method.
By August, most rain barrels have run dry, making this the perfect time to clean out any debris in the remaining grey water, along with any mosquito larvae. West Nile Virus, Zika Virus, and many other diseases are transmitted by mosquitoes, so it is important to regularly eliminate any standing water. Mosquito dunks should be added to any standing water every 30 days.
Hot weather means trees need more water. Trees planted in a lawn that is being watered regularly will still need a deep watering 2 or 3 times during the summer, or more, depending on the weather. Solitary mature fruit and nut trees will need a deep watering every 3 - 4 weeks, while younger trees will need to be watered every 2 weeks. Ideally, there is an irrigation ring around each tree at the drip line.
August is an excellent time to start seeds for California's winter crops. Spinach, beets, lettuce, arugula, broccoli, Brussels sprouts, cabbage, cilantro, bush beans, fava beans, leeks, radishes, and peas can all be started in small containers for transplanting after summer crops are done. This gives you a head start on the cooler growing season, just be sure to keep the soil moist. A thin layer of vermiculite can help retain moisture in those pots.
Remember that your plants are not the only things that need extra hydration and sun protection in summer! You do, too! Be sure to drink lots of water, slather on the sunscreen, and wear that hat!
Greens bolt and wither
Searing heat and glare above
Seek shade and cool water
July can get too hot to spend much time outside. Early morning and late evening make working in the garden far more comfortable, but leave most of the heavy work to the plants as they produce leaves, stems, and fruit in response to all that sunlight. The best things you can do for your garden in July is irrigate properly and monitor plants for pests and diseases.
Monitoring for pests and diseases
You know what they say about an ounce of prevention. Well, here are a few helpful July ideas that work to prevent problems in the garden before they have a chance to get started:
It’s all too easy to forget about the trees in your landscape, but scorching summer heat and an extended drought can be devastating. Trees are a big investment of time and space, so be sure to include them in your watering plan. The only exception is California live oaks - they are accustomed to hot, dry summers and watering them only makes them susceptible to disease.
There is no fixed magic formula for watering plants in the garden. There are simply too many variables, such as plant variety and age, soil structure, feeding practices, sun and wind exposure, overall plant health and life stage - you get the idea. The best way to assure that your garden plants are getting the water they need is to learn as much as you can about the specific varieties and their water needs. This information will help you to provide them with the growing conditions they need. Be sure to water tomatoes, peppers, eggplant, and squash consistently, to avoid blossom end rot.
During summer, container plants may need a drink practically every day. Just be sure to avoid overwatering - a drowning plant looks an awful lot like a plant that’s dying of thirst. An inexpensive moisture meter ($10-15) can help prevent irrigation errors. Also, be sure to get those containers up off the concrete. Even the smallest air space underneath can significantly reduce temperatures for potted plants.
If you still have a lawn, be sure to raise the blade on your mower. Taller grass shades the ground, reducing water loss and stabilizing soil temperatures. By the end of July, your lawn will probably be brown, and that’s okay. Keep watering it. The root system will stay alive, and green shoots will come back in the fall after temperatures go down. [I use water from my washing machine with no negative results and my lawn stays green far longer.]
Basil and other heat lovers
It is finally warm enough for crops such as basil, melons, eggplant, and peppers to really thrive. These are some of my favorite plants. You can train melons up a trellis or ladder, and you can never have too much basil. If you have more than you can use fresh, simply whip up a batch of pesto and throw it in the freezer. Come January, you’ll be glad you did!
Mulch and top dressings
Summer is an excellent time to mulch unused garden areas. As it breaks down, the organic material will improve soil structure and add valuable plant nutrients. This is particularly helpful if you have compacted soil. Until it does break down, mulch stabilizes soil temperatures, reduces weed competition, and helps soil retain water. In the same way, top dressing the plants in your garden or foodscape with aged compost is a trouble-free way to add nutrients to growing plants without applying chemical fertilizers.
Fire safe gardening
Summer fires can be devastating, but you can slow the spread of fire with fire safe gardening. Rural areas of California and other states are required, by law, to maintain a defensible space around homes. You can use the same ideas to protect your home and family:
And leave the fireworks to the pros.
As you lounge in the shade with an iced tea, remember that July is an excellent time to consider what cool season crops can be added in fall!
Longer days of sun
Burst forth fruits and leaves
June is a busy month in the garden. Rising temperatures and strong growth increase the need for irrigation. Sowbugs and other pests seem to be everywhere. Fruits, flowers, and mulch are the name of the game when it comes to June garden chores.
Bees are everywhere you look, collecting pollen and nectar for their families (and pollinating nearly all of our garden crops). If you see a swarm, don’t panic. Swarming bees are surprisingly docile. Their bellies are full of honey and they are simply looking for a new home. Contact your local Bee Guild or Master Gardeners for information on swarm collection. Under no circumstances should honey bee swarms be sprayed with insecticides.
*Contrary to popular belief, eggshells are too hard to properly breakdown in the soil on their own in a reasonable period of time. Eggshells do not dissolve in water and must be ground very finely to have an impact on the soil. If you suspect insufficient calcium, send out a sample for a soil test.
QUARANTINE WARNING: MOST OF SANTA CLARA COUNTY IS UNDER QUARANTINE FOR CITRUS, DUE TO THE ASIAN CITRUS PSYLLID. CHECK THIS MAP TO SEE IF YOU ARE AFFECTED.
June usually provides an abundance of fruit. If damaged fruit is seen, take a closer look. If the fruit looks chewed on, it’s probably rats or squirrels. Personally, I use Bobbex-R to deter these destructive, disease-carrying pests. My dogs enjoy helping out, too! I also use traps to kill rats. It’s a bit disgusting, but it works.
Fruit drop and fruit thinning
Don't be concerned if your fruit trees suddenly drop a majority of their blossoms or immature fruits. This normal behavior, called June drop or blossom drop, prevents trees from producing more fruit than they can support. To help your trees create the highest quality and best sized fruit, this is the time to thin fruits.
If you haven’t already, June is a good time to check irrigation systems for leaks. Drip systems should be flushed and emitters checked for clogs. This is also a good time to test to see where, exactly, sprinklers are spraying and where they are not. There’s no sense in wasting precious water in urban drool and the spray should never hit tree trunks.
Mulching is one of the best things you can do in the garden, especially in June. Mulching stabilizes soil temperatures, reduces weeds, and helps the soil retain moisture. Aged compost, placed on top of the soil, is mulch. Tree trimmings make excellent mulch and they can be acquired for free from tree trimming companies! As mulch breaks down, it adds valuable nutrients to the soil and improves soil structure. Just make sure that mulch is kept away from tree trunks and that it isn’t too thick. Generally speaking, a layer of 3 inches is just right. Too much mulch can interfere with gas exchanges.
If you haven't started already, June is an excellent time to plant those heat-loving cucumbers, peppers, squashes, tomatoes, eggplants, and melons. Also, you can create an ongoing harvest by succession planting radishes, beans, and other determinant crops.
Be sure to put on your sunscreen, wear a hat, and keep those tools clean and sharp as you enjoy the garden in June!
As busy as bees
We pierce the warming topsoil
With dreams of freshness
May is one of the busiest months in the garden. Temperatures have warmed enough for us to begin planting in earnest. Weeds, pests, and beneficial insects are out in force. And it's gorgeous outside!
Aerate the soil
Our San Francisco Bay Area soil is heavy clay. This means it can hold on to lots of water and nutrients, but it can be difficult for roots, earthworms, and soil microorganisms. You can hire a professional aerator to come in with their heavy equipment to punch plugs out of your soil. While the machine creates its own soil compaction, the plugs really do make a big difference in soil health. Or, you can do what I do, which is to contact your local tree trimmer and ask for a load of tree trimmings. It won’t be the pretty bagged variety, but it will contain chipped twigs, leaves, stems and branches that can be spread on top of the soil as a mulch that will profoundly improve your soil structure. In 2012, when we bought our home, the soil was more like concrete. Now, thanks to mulches of tree trimmings, my soil is rich and black, loose, and filled with earthworms and beneficial microorganisms. For free.
Bees are very active in May. There is simply so much pollen and nectar to collect! Sometimes, a honey bee colony may swarm. If you see a swarm, don’t panic. As in any other time when working around bees, remain calm, move gently, and give them their space. Contact your local Bee Guild or Master Gardeners to have swarms removed.
Bulbs and other flowers
If flowering bulbs were looking crowded during the recent bloom time, delay digging them up to separate until after all the foliage is completely dry. Bulbs pull important nutrients from these leaves to help start up again next spring. Bulbs that are dug up and separated can be replanted in a new location, gifted to friends, or stored in a cool, dry, dark location until fall. If you want fall blooms, plant now.
They are countless varieties of plants that perform well in containers. Do them all a favor in May and get them off that soon-to-be hot concrete patio. Creating even the smallest space under container plants can reduce the roasting effect, which means they will need less water. Speaking of water, warmer temperatures mean container plants will start drying out more quickly. Water as needed.
Many flowers are in full bloom in May. To encourage plants to continue creating blooms, remove spent flowers as soon as they are seen. This also reduces habitat for many pests and diseases. Pinch back borage, petunias, and fuchsias to prevent plants from becoming top heavy.
May is the time fireblight shows itself in the Bay Area. Fireblight is a bacterial disease that makes plants look as though they had been damaged by fire. It attacks apples, pear and quince, most often, but can also infect ornamentals, such as toyon and pyracantha. Very often, the growing tip folds over into a shepherd’s crook shape. Fireblight can kill a mature tree, so complete removal of any diseased tissue is critical. Sanitize pruners with a household cleaner, such as Lysol, between each cut to prevent reinfection. The final cut should be 8-12 inches below the diseased area.
May should be the time when fruit trees are covered with immature fruits. Thin those fruits now or regret it later. Too much fruit in one place means none of them taste as good as they might have. It also creates habitat for pests and disease. Apples should be thinned to no more than 3 fruits to a cluster, or one fruit for every 6 inches of branch. Apricots and other stone fruits need 4-6” between fruits for optimal growth, flavor, and sweetness. Also, be sure to check apples for codling moth damage.
If you still have a lawn, be sure to water it as early in the morning as possible. That way, the water isn’t lost to evaporation and the grass has time to dry out during the day, reducing the chance of fungal diseases. For the most part, I use water from my washing machine to water my lawn and it has been working very well. Check the lawn for weeds such as spurge, burclover, and whatever happens to invade your neighborhood. When mowing, set the blade height as high as you are comfortable with in summer. Taller grass shades the soil. This reduces evaporation and it makes the soil more comfortable for valuable earthworms and microbes.
Mulch and compost
Compost and mulch are two of the best things to add to any landscape. They add valuable nutrients to the soil, improve soil structure, and stabilize soil temperature. In our heavy clay soil, mulch prevents the baked concrete look we have come to expect in summer. [An important note about soil additives - while it may sound right to add sand to clay soil, to reduce compaction, it ends up creating concrete. Don’t do it!]
Slugs & snails
Slugs and snails can devastate young May seedlings. Applying non-toxic slug and snail bait lightly around new planting areas can save the crop. While there are more effective baits, those made with iron phosphate are not toxic to pets and wildlife and I have found they work well enough.
Before you start applying fertilizers and fungicides, collect a soil sample and send it out to a lab. [I use the UMass lab, but there are many to choose from]. The information provided in soil test results is invaluable. More often than not, your soil does not need more of all the nutrients found in a bag of fertilizer. It may only need some, or, in my case, it only needed iron because it held an excess of everything else. Simply adding more fertilizer can create nutrient imbalances that make it difficult for plants to absorb what they need. Get a soil test. It’s worth it.
This is the most welcome news of the season in the Bay Area. Nearly all summer growing plants (tomatoes, cucumbers, melons, squash, beans, corn, and peppers) can be put in the ground in May. If you are using transplants, be sure harden them off gradually or they may lose much of their vigor and productivity. Hardening-off simply means placing them outdoors in a protected location for a few hours. Slowly increase the time over a couple of weeks. Be sure to stake tomato plants now, while they are small. This can be done in tandem with quarantining new plants. And add straw under melon, squash, and strawberry plants to reduce fungal infection.
If verticillium wilt occurred last year, it is important to plant members of the nightshade family (tomatoes, potatoes, peppers and eggplant) someplace else. Verticillium wilt is a fungal disease that shows as yellowing older leaves, at first. Then, as the disease spreads, wilting occurs. Young plants nearly always die. Since the fungal spores can remain in the soil for 10-15 years, crop rotation is the best prevention.
California’s drought is continuing, despite the fair bit of rain we have received so far. The truth is, the Golden State has always been drought-prone and we would be wise to learn to live accordingly. When water restrictions were first implemented, I vowed to take meaningful steps to reduce our water consumption. As a result, we now use only 25% of the water we used to use! Surprisingly, my garden has not suffered and neither have we. These steps can help you conserve water while still caring for the garden:
Just as young garden plants are really kicking it into high gear in May, so are the weeds. Take my word for it, pulling them while they are small, and before the soil is baked, is much easier than later. Weeds take precious water and nutrients from garden plants. In most cases, the sooner they are gone, the better.
So, put on the hat and sunscreen and get out there in that May garden!
April chirps and sings
Splitting shells and seeds and blooms
April is a busy month in California gardens. With scorching summers on a not-too-distant horizon, flowers, weeds, and every other living thing are striding toward sunlight. Cool nights may hold this rampant growth in check for another week or two, but most gardeners have plenty of April garden tasks to keep them occupied.
Before you get too excited about planting, take a few minutes to inspect your property for mosquito breeding grounds. Mosquito larvae can grow in as little as one tablespoon of water. Bird baths, rain barrels, clogged rain gutters, and planter pot saucers can all harbor these pests. Mosquito dunks, also available as granular bits, contain a bacteria, Bacillus thuringiensis israelensis (Bt.i), that is deadly to mosquito larvae but harmless against all other living things. You can also use Bt.i against fungus gnats. Mosquitofish can also be used to reduce mosquito populations.
Plum bud gall mite
As of January 2019, we have a new pest in northern California. Be on the lookout for abnormal growths, or galls, on almond, apricot, plum, pluot, and many other fruit and nut trees. These tiny eriophyid mites are only 1/100th of an inch long. If you have a 20x hand lens, you may be able to see them. They can be a translucent yellow, pink, white, or purple, with two pairs of legs up near the head. You are more likely to see galls on new shoots and fruit spurs that plants produce in response to these invaders. This new pest threatens tens of thousands of fruit and nut trees in California. If you happen to see this new pest on your trees, please contact your County Extension Office right away.
Tree Trunk Painting
If you didn’t whitewash your tree trunks (and exposed branches) in March, there is still time to provide this valuable sun protection. Trunks and branches that get too much sun exposure can be damaged, causing the bark to split and peel. This provides pests and diseases with easy access to your trees’ inner workings. A simple mixture of half water and half white interior latex paint is all you need to protect your trees from sunburn this summer.
This is also a good time to replace last year's sticky barriers. The protection from crawling insects that these simple barriers provide cannot be overstated. Sticky barriers block those crawlers (and slugs and snails) from getting up into your fruit and nut trees. This is especially helpful when it comes to ants, which will protect and farm aphids. Over time, the goo dries, making it ineffective. Also, the tape tends to pull away from the trunk, creating an easy trail for pests. Gently remove the old tape, inspect the trunk, and apply a fresh sticky barrier. Just be sure that you do not use painter's tape to create sticky barriers. The moisture from the goo will cause the tape to disintegrate and damage the tree's bark.
Codling moth larvae can devastate apple, plum, pear, and walnut crops. The larvae pierce the fruit and burrow into its core, where it then feeds on the fruit, making it inedible. On apples, look for tiny dimples with a small hole in the center. These holes are usually filled with frass (bug poop). Trees should be monitored every week for signs of infestation. Infested fruit should be removed and discarded, to break the codling moth life cycle. Pheromone traps can be hung in isolated trees, but you need to understand that these traps attract codling moths to the tree. The traps are really a population monitoring device, not a control measure. Fruit can be bagged for protection, but this is a very labor intensive method. Kaolin clay application is an excellent organic control method. Heavy infestations may require the use of pesticides on the moths, before fruit is affected.
As flowers begin blooming, you can increase production by removing spent blooms.This works equally well for roses and artichokes. Take a look at buds further down the stem and clip just above a bud that points in the direction you want the new growth to go. Deadheading can help the plant structurally and it allows for good airflow, as well as stimulate new flower development.
As difficult as it may be for gardeners to thin out fruit and young plants, it really is necessary for the optimal growth of remaining plants. April is the time to thin fruit on fruit trees, such as apricots, peaches, apples, pears, nectarines, and plums. Crowded fruit doesn’t get as big as it could and it encourages fungal diseases. Close-quartered fruit also provides great hiding places for pests. The best fruit grows from strong flower buds in full sunlight. The basic rule of thumb for thinning fruit is to leave one fruit per spur, with fruit 4-6” apart. Apricots, nectarines and peaches are normally thinned when the fruit is 1/2-3/4” in diameter. Nut trees do not need to be thinned. Seedling plants should also be thinned according to seed packet or other reputable information. This allows each plant to reach its full potential and it reduces problems with pests and diseases. Rather than pulling seedlings out by the roots, snip them off at soil level. This reduces disruption to the remaining (delicate) root systems and leaves valuable soil microorganisms in place.
Spring rains bring moisture that can cause many fungal diseases. Anthracnose, brown spot, powdery mildew, sooty mold, and verticillium wilt should all be watched for and treated. Many of these conditions can be avoided with pruning that allows good air flow and irrigation that does not come from overhead. Overhead watering splashes millions of fungal spores onto uninfected plants, spreading the disease (plus, it wastes water through evaporation).
Irrigation & greywater
As temperatures rise, irrigation becomes more important. Containers and raised beds will begin to dry out and need to be checked every day. If the irrigation system wasn’t inspected in March, be sure to do it now. Greywater, from sinks, washing machines, and rain barrels can be used to irrigate ornamentals and lawns. I use water collected from the shower, as it heats up, to water edibles.
To add nutrients, reduce weeds, and to help retain moisture, nothing beats mulch. Wood chips and aged compost both make excellent mulch. You can request free wood chips from local tree trimmers. To stop weeds from growing, the mulch should be 4" to 6” think. I used to recommend a layer of cardboard or newspaper be placed underneath, but then I learned that these materials attract termites and voles. Cardboard also slows gas and water exchanges. Be sure to keep mulch at least 8” away from tree and shrub trunks, to avoid fungal diseases, such as crown rot.
If you have Navel orange trees, the crop will be ripening in April. Oranges left on the tree too long will dry out and become inedible. Instead, harvest the entire crop by the end of the month and you can make my new favorites, Cardamom Orange Marmalade, Orange Cumin Chutney and Spiced Oranges. Once canned, these delicious condiments make lovely gifts. You’ll want to be sure to save plenty for yourself - it’s that good! Valencia oranges will ripen during the summer and they make excellent juice. April is a good time to add nitrogen for orange trees. One-year old trees will need 1/10 of a pound of nitrogen, while mature trees need approximately 1-1/2 pounds. These amounts should be divided into three different feedings in April, June and August. Blood meal is an excellent source of nitrogen, without all the fillers.
QUARANTINE WARNING: MOST OF SANTA CLARA COUNTY IS UNDER QUARANTINE FOR CITRUS, DUE TO THE ASIAN CITRUS PSYLLID. CHECK THIS MAP TO SEE IF YOU ARE AFFECTED. ALSO, BE ON THE LOOKOUT FOR ORIENTAL FRUIT FLIES. IF EITHER PEST IS SEEN, PLEASE CALL THE PEST HOTLINE AT 1-800-491-1899.
Fennel, rhubarb, and asparagus provide many years of food production and April is a good time to plant. Fennel and rhubarb will take up a good amount of space, so be sure to keep mature sizes in mind.
Temperatures have finally reached the point when gardeners can plant most herbs, leafy greens, and other salad ingredients. Lettuce, arugula, spinach, bok choy, basil, parsley, cilantro and radishes can be planted every couple of weeks in succession for a continuous harvest until temperatures get too hot.
Most vegetable crops can be planted in April, in warmer regions. Potatoes, bush and pole beans, corn, cucumber, summer and winter squash, and tomato seeds put in the soil now will begin their journey toward fruitfulness. Be sure to read packet directions for planting depth, spacing, and sun requirements for the best results.
One of the most important April garden tasks is to get rid of those weeds. Since they can go to seed faster than everything else in the garden, removing them out now will save you countless hours of work later on, in the summer.