Garden Tips for May

Peyton Ellas is a UCCE Master Gardener and is owner of Quercus Landscape Services and Auntie's Home Grown Farm in Springville.

The story of this month is the brilliance and abundance of flowers, in our gardens and in our wild lands. But have you noticed the foliage also seems especially vigorous and healthy? Along with my plants, native and exotic, birds, reptiles, amphibians, mammals, and insects all make the most out of spring weather. Warming soil combined with warm (not hot) air temperatures means growth and vigor. Take time to notice if you too, being part of the garden balance, feel energetic and supported on these spring days.

Planting: Almost everything can be planted now, especially early in the month. Try to finish planting in the ornamental garden before summer weather arrives. You can plant water-loving plants through summer, but even for them, transplant shock will be lessened if you can plant while we still have cool nights. Bulbs, tubers, and corms to plant are dahlia, gladiolus, and tuberose. Succulents are fine to plant now too, as are avocados, citrus, bougainvillea, and other frost sensitive plants. Summer color can liven up both the ornamental and edible gardens. Species to plant now include zinnia, marigold, petunia, sunflower, cosmos, and impatiens. If a few plants didn’t make it through the winter because of flooding or frost, this is a good month to replace them. Try a new California native! It’s still valid to look for climate-adapted ornamental plants and limit the dependence of your ornamental garden on heavy irrigation during the hot summer months. 

It’s finally time to plant heat-loving vegetables like tomatoes, peppers, basil, eggplant, summer and winter squash and tomatillos. Don’t worry about some shade in your edible garden. Many summer garden vegetables do fine if they get at least six hours of sun a day, which is just about half a day. Heat lovers to plant in the full 14 hours of sun we can expect are winter squash, melon, okra, beans, and corn. Why not try a three-sisters garden of corn, beans, and squash? If you have an established garden, care for your soil by adding straw, compost, and composted manure or, if you must, store-purchased amendment. If your soil is healthy, your plants will need far less pest and disease management, making the garden healthier and less work. 

You may need to protect your vegetables from gophers with root caging. Where I live in the foothills, I need to protect my edibles from all kinds of wildlife with both root and foliage/fruit barriers. But it is worth it when harvesting time comes. And I like having wildlife (many of them are food for raptors and coyotes, which I also like having around) so I do not use poisons but rely on exclusions and tolerating some loss. Which is part of IPM (Integrated Pest Management).

Maintaining: Check your watering system and adjust as the weather warms. Your new transplants will need to be supplied with water on a regular basis through late spring and right into summer. Don’t expect even low-water-use plants to survive on no water during their first year. Deep water stone fruit, apple, pear, and nut trees. You must water your edible garden as much as it needs to keep it healthy.

For established gardens, the top several inches of soil can dry out for almost all plants in the well-mulched garden and in whatever lawn you still have. Many people over water their lawns, especially in late spring. This encourages disease and insect problems. Mature trees and shrubs probably have plenty of ground water reserves this year; let’s observe and see where we can retrain ourselves about our summer watering.

Prune spring-blooming shrubs like camellia, lilac, Ceanothus, and hydrangea as they finish flowering. Pinch back fall-blooming chrysanthemums until July. Deadhead roses (remove old flowers) to encourage repeat blooming. Trim off suckers from the base of roses and from trees, and take out any dead branches now that they’re fully leafed out. If you haven’t already, thin your nut and stone-fruit trees when the fruit are small to improve fruit size and quality. How much will you realistically consume? Thin, and then wait a day or two and then thin some more. Branches may break if they are overloaded with fruit. For young trees less than five years old, allow only a few fruits to grow to maturity so the tree can put more energy in root and shoot growth. Cage young trees with field fence or rabbit wire and sturdy posts to prevent damage from ground squirrels, rabbits and deer in the foothills and mountains.

Continue with weeding. This seems to be a good year (?) for weeds! Two years of abundant rains have given the invasive annual grasses and broadleaf perennials extra vigor and reproduction energy. I am already thinking of changing my weed management system for next year to better control them. I don’t prefer a sterile garden, but the weeds should not be the dominant species.

Compost and/or mulch if you haven’t already. Keep wood mulch at least six inches away from tree trunks. Raise the mowing height to three inches for all types of lawn to shade out weeds and keep roots cooler.

Monitor the edible garden for common warm season insect pests: earwigs, aphids, slugs, snails, and grasshoppers. Blast soft-bodied insects like aphids with a stream of water. Insecticidal soap is a good all-purpose insecticide for many insects, and it doesn’t kill as many beneficial insects as broad-spectrum powders and sprays do. Try to tolerate some damage, to feed garden friends like birds, spiders, lacewings, ladybugs, assassin bugs, lizards and praying mantis. Many native plants, including native milkweed, tolerate aphids, milkweed bugs and monarch caterpillar damage. Hand pick tomato/tobacco worms, hoplia beetles on roses, snails, and slugs. Leave rolled newspaper traps or put a little oil into opaque bottles and leave them laying sideways under garden plants to trap earwigs. The traps need to be put in the waste every morning until the population is diminished. Control scale (they appear as little bumps on stems of citrus, bay, and other plants) with summer horticultural oil. You may need to repeat the application in June. Follow package instructions to avoid harming your plants.

Fertilize your container plants now. Once a year is usually enough for most containers. Once every three years may be all that is needed for California native plants in containers. You may never need to fertilize your succulent and cactus. Fertilize azaleas, camellias, and gardenias with fertilizer labeled for them. Fertilize citrus with fertilizer labeled for them. Citrus in containers needs to be fertilized at least once a month during their blooming and growing season to produce well. Citrus in the ground should be fertilized this month and then not again until next year. Fertilize your warm-season lawn and groundcovers with an all-purpose product to promote vigorous growth and help prevent weeds. If you haven’t already, fertilize your roses. You may find that compost is all you need; don’t feel pressured to add store-purchased fertilizer if your plants are vigorous and healthy. Sometimes we think we “must” do things, but do we need more growth that we will need to prune later? Do we need more fruit that will just end up on the ground or compost bin? Most low-water-use plants are better off without fertilizer to keep them longer-living and more compact.

Conserving: Don’t disturb your bee nesting and bird houses. Observe your trees before having the tree trimmers come to make sure you’re not disturbing an active bird nest. Leave a little radish, mustard and broccoli blooming in the edible garden until seed set to support pollinator insects. Consider adding a new plant for the wildlife. Do you have room for a quail bush (Atriplex lentiformis), mulefat (Baccharis salicifolia) or California fuscia (Epilobium californica)? Do you have room for yarrow, California buckwheat or California native milkweed? Native milkweed has pink and white, not yellow or orange, flowers. Can you dedicate a space in the garden that is less manicured? This will support the greatest diversity and number of native bees, beneficial insects, lizards, toads, and birds. The abundance of healthy life in balance with other lives is what makes a beautiful garden.

Gardeners will be live to answer your questions on Saturday, May 11, 10 a.m. to 2 p.m. at the Luis Nursery Plant Clinic, Caldwell and Mariposa, in Visalia. You can also contact them at 559-684-3325, or visit their web site at

This column is not a news article but the opinion of the writer and does not reflect the views of The Sun-Gazette newspaper.

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