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

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.


Container plants

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.


Deadheading

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.


Fireblight

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.


Fruit trees

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.


Lawns

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.


Soil test

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.


​Start planting!

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.


Verticillium wilt

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.


Water

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:

• Collect water from the bath or shower as it warms and use it to water plants.
• Collect water from boiling pasta and vegetables and use it to water plants.
• Inspect spigots, hoses, sprinkler and drip irrigation systems for leaks.
• Water early in the morning, and water deeply and less frequently.
• When adding new plants, pick varieties that are suited to the local microclimate.
• Avoid urban drool by setting sprinklers to go through a series of pulses. Start with just a few minutes to allow hydrophobic soil to absorb the water, rather than run off.
• Apply organic mulch or wood chips everywhere.
• Turn off faucets while washing hands, brushing teeth, or shaving.
• Use only the minimal amount of fertilizer. Excess fertilizer forces plants to grow faster than they can maintain without a significant increase in water use. Without a soil test from a reputable lab, you don't know if fertilizers are needed.
• Be aware that the drought brings more wildlife into yards as they search for food and water. You may want to provide a water source, such as a birdbath, but be sure to not create a mosquito breeding ground.

Weeds

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!

Citrus

Citrus pruning should not be started until after March 15th, but now is the time to seriously inspect for mummies. Mummies are those shriveled up, fuzzy gray oranges that house millions of fungal spores. When removing mummies, try to disturb them as little as possible, or cover them with a plastic bag before removing them from the tree. If a citrus tree shows signs of chlorosis (yellowing) on older leaves, it may indicate a nitrogen deficiency. Interveinal (between leaf veins) chlorosis usually means a micronutrient, such as iron or manganese, is needed. Our soil tends to be very low on iron, but you can’t know for sure without a soil test. After the danger of frost has (nearly) completely passed, on March 15th, give citrus trees a good pruning. Just be sure to keep a look out for nests. It’s that time of year!


Compaction

Walking on wet ground causes soil compaction. This is especially true for the Bay Area's heavy clay soil. Rather than walking on wet soil, stay on paths, install stepping stones, or just wait for it to dry. Compacted soil is particularly difficult for young roots to move through, and it can cause drainage problems.


Disease prevention

Winter and spring moisture provide the perfect habitat for many pathogens. You can prevent diseases, such as fireblight on apple, pears, quince, and loquat, with fixed copper sprays. You can also reduce the chance of powdery mildew on grapes by applying sulfur at this time.

Feed young trees

As young trees continue putting out new roots, shoots, and leaves, they will benefit from being fed in March. Check the specific species of tree for more information on how much fertilizer should be provided.


Irrigation

Another common March task is to inspect and repair sprinklers, drip systems, and water collection systems. How do you know if you have an irrigation leak? It can be difficult to spot, especially if it is small. The most common indication is an area that gets and stays wet longer than everywhere else. Sprinklers should be aimed so that they do not hit tree trunks, walkways, driveways, or sidewalks. The former can cause fungal diseases and the latter creates wasteful urban drool. 


Pruning

March is also a good time to prune out dead branches and twigs from fruit and nut trees and ornamental trees and shrubs. It is easier to see the structure of each plant before it is covered with leaves.


Roses

If your roses haven’t already started producing leaves and blooms the way mine have, March is a good time to prune them for better airflow and structure. You can also start feeding roses in March, and you may need to spray for black spot. Black spot is a fungal disease that loves moisture. As dew collects on rose leaves, the fungus reproduces astronomically. You can use neem oil or a fungicide. 


Seeds

March is an excellent time to start planting your summer garden. In the Bay Area, you can still direct sow many cool weather crops, such as beets, broccoli, cabbage, carrots, cauliflower, chard, lettuces, spinach, bok choy, fennel, kale, mustard greens, parsnips, and turnips. And it's not too late to install that asparagus bed! March is an excellent time to add cilantro, dill, and parsley to your garden, but wait for warmer temperatures before planting basil and peppers. Potatoes and radishes can be planted now, and you can start tomatoes and peppers in pots, but only if you can protect them from nighttime cold. Otherwise, wait for April, when soil temperatures rise and the serious planting begins! As you dedicate seeds to a specific location, make sure to read the seed package labels for things like mature size, thinning requirements, and sunlight needs, and be sure to use plant markers!

​
Slugs and snails

Our warming temperatures and moisture work together to create the perfect habitat for slugs and snails. These mollusks can devastate seedlings in a single night, so be prepared. I urge you to follow the link to slugs and snails to learn more about the specific ingredients in different bait products. They are not created equally, and some can harm pets. Choose accordingly.


Soil test

If you have not conducted a soil test recently, now is the time. Find out what is in your soil before you start adding plants. This will help avoid nutrient imbalances that can wreak havoc on plant health.


Weeds

Walk through your garden in March and you are sure to see weeds coming up in every location imaginable (and a few unimaginable places!). Your Number One March garden task is weeding. Since some weeds can go to seed in as little as a week, now is the time to cut them off at ground level with a hoe. Wait until later in the season and thousands of seeds will already be sown. Healthy weeds make great additions to the compost pile. Personally, I feed them to my chickens.

​Enjoy the early blossoms!

In many parts of the country, winter snow still holds everything in thrall, but California is a different story altogether. Rains have brought us some much needed moisture (though we really need more!) and longer days are coaxing new shoots to emerge. This is the stuff of February gardens in San Jose. 

Bare Root Trees

There is still time to plant bare root trees. Many of these plants have been sitting in nurseries for a few weeks. Soak them in a bucket of water for several hours after trimming off any damaged bits. Dig a hole that is shallow and wide. There is no need to amend the planting hole. Spread the roots out horizontally for the best growth. Be sure that the crown is a few inches above the ground to avoid crown rot. The crown is where the trunk meets the roots. ​


​Rather than tamping the soil down, mud in your new tree with water. This eliminates any big air pockets that might dry roots out while helping them stay upright. Speaking of supports, only provide tree supports if absolutely necessary and remove them as soon as they are not needed. Water regularly, unless it’s raining. Avoid fertilizing until 6-8” of new growth appears.

Citrus

Harvesting citrus fruit is a common February garden task. Citrus trees tend to produce heavily every other year and February is normally harvest time. If you don’t harvest your oranges, other things will! Squirrels, snails, and rats can make a mess if fruit isn’t harvested. Heavy rains can cause fruit splitting. These fruits attract pests and diseases and should be removed from the tree and composted or discarded. If your tree produces a bumper crop this year, try making orange marmalade! ​​

Dormant sprays

If pests or diseases were a problem on your fruit or nut trees last year, February is a good time to apply dormant and delayed dormant sprays of horticultural oil and/or fixed copper, depending on the tree species and the problem. Horticultural oil will suffocate pests such as aphids, mites, and scale insects before they can cause damage. Fixed copper is used to reduce the likelihood of many fungal and bacterial diseases, including fireblight, peach leaf curl, and bacterial blight. Be sure these treatments are applied before buds begin to open.


Mosquitoes

Rain also creates countless habitats for mosquitoes. Mosquitoes are a vector species that can carry the Zika virus, dengue, yellow fever, West Nile virus and many other nasty conditions. Walk through the garden and look for potential mosquito habitats. They only need about one tablespoon of stagnant water to start reproducing. Adding mosquito dunks to rain barrels, fountains, and birdbaths goes a long way toward eliminating the local mosquito population.


​Peppers and tomatoes

To jumpstart a garden, one February garden chore is to start peppers and tomatoes indoors, in a greenhouse, or under a protective cover. I used my pumpkin ladder draped with shade cloth. Hot peppers, in particular, need a long growing season to develop the best flavors. Seed heating mats, designed for seed starting, can keep pepper seeds warm enough to germinate. As they grow, transplant seedlings into larger pots until it is warm enough to move them outside. If your seedlings get too leggy, in a condition called etiolation, they are not getting enough light.

Weeds

Lawns may look green, but is it the right kind of green? Weeds grow more quickly than many garden plants. Take a look at what it is actually growing in your lawn. This is a great time to pull weeds - before they go to seed and while the ground is moist, making it easier to pull them up by the roots. Plus, the disruption provides loosened soil for the spreading roots of more desirable grass species. Pull weeds from around perennial plants, as well. They will need all the nutrients they can get for spring growth. Pulling weeds now is one of the most productive February garden chores you can do.


Whitewashing

After pruning and spraying your trees and applying a sticky barrier, you should protect them against sunburn damage by painting exposed areas with a mix of one part water and one part white latex paint. Do not use any other type of paint, as many of them can interfere with your trees' ability to breath. Whitewashing reflects the sun's damaging rays away from the bark, helping it to stay intact. Bark is an important protective barrier against many pests and diseases.