Gardening Tips for April

By Peyton Ellas

UCCE Master Gardener

Gardening in April is one of life’s great pleasures. The weather is generally pleasant, at least in the mornings, and there are usually still plenty of flowers, vibrant foliage and wildlife activity to add interest. Well designed and managed gardens are a place of rest, therapy and enjoyment at all times. How about celebrating Earth Day on April 22 in a new way? Perhaps by planting a tree, or new pollinator-supporting plants, or by building a compost bin, or getting out the paint and brushes or pencils and appreciating the originality in our gardens? 

PLANTING: We can plant just about anything in April, especially in the early part of the month. Bulbs to plant now include gladiolus, lily and dahlias. Plant early in the morning or late in the day, especially on a hot or windy day. Make sure your irrigation system is ready to go before you plant. If your garden is in mid to high elevation foothills and low mountains, you can plant as soon as the snow melts. 

In the edible garden, plant summer annuals like tomatoes, peppers, eggplant, summer and winter squash (wait until May for pumpkins), beans, corn, cucumber, melon and okra. You can also still plant radishes, greens and onions but be prepared to harvest baby greens and green onions; they will grow and flower seemingly overnight in the lengthening days and warm temperatures. This year I am going to try red hibiscus (H. sabdariffa) again, something I grew several years ago. We harvest the flowers, remove the seed pod and dry them for delicious home-grown herbal tea. Like everything in the okra family, I’ll have to watch the ants and aphids, but it will be worth the extra attention. 

MAINTAINING: Just as our plants are growing quickly (even Manzanita has a growth spurt in April), so too our amazing and adaptable insect pests are flourishing in the warm days and cool nights of spring. Monitor for aphids on all edible plants and many ornamentals, especially on roses. Other insects to watch for include slugs and snails, whitefly, and earwigs. Don’t immediately reach for a broad-spectrum insecticide; they kill beneficial insects right along with the pests. Use our Master Gardener website or ask us for suggestions using the IPM method. Exclusion with row cover cloth may mean an initial investment, but less than you would spend on insecticides over the life of the fabric, and it is efficient. My method also involves ruthless culling if an individual plant is covered in aphids. I have pet sheep, so nothing goes to waste! You can put aphid plants in the green waste bin with a lid, but not in the compost unless you can be sure it will get 160°F. April is also the month to monitor powdery mildew in grapes, fire blight on apple, pear, Photinia and other susceptible species, and codling moth worm on apple, pear and quince. Look to our IPM website for how to manage each of these: ipm.ucanr.edu

Although California native and other Mediterranean-climate plants do not require fertilizer, we do fertilize many exotic plants this month. Use fertilizer labeled for roses on roses of all types. Use fertilizers labeled for acid-loving plants on azaleas, gardenias and rhododendrons after they flower. When spring bulbs finish flowering, snip off old blooms and feed with an all-purpose fertilizer. Do not trim or braid foliage leaves—they are taking up nutrients for next year’s flowers. Trim after they turn yellow. If citrus leaves are puny or showing dark green veins with pale middles, then spray them with a liquid cleated iron/zinc mixture. This works on gardenias, too. Fertilize lawns: generally, it’s best to do two half-strength feedings two months apart, rather than one strong.

Prune winter and spring flowering shrubs when they finish blooming: azaleas, camellias, forsythia, lilacs, ceanothus, native sage and flowering quince are some examples. Prune citrus and avocado if necessary. You can continue to prune deciduous trees if you haven’t yet; it may slow the growth a little but won’t hurt them. Thin stone fruits while the fruit is still tiny, to about six-to-eight inches apart. Mow lawns to three inches tall. Scalping encourages weeds and other pests.

CONSERVING: Top dressing with compost is excellent for all soils and microclimates. A layer of two inches or more of mulch should become standard practice; it does so much to encourage healthy soil and healthy, vigorous plants. Inorganic mulch (rock) won’t break down into organic matter for beneficial microbes, but it still helps regulate soil temperature, protects the soil from erosion, helps reduce weeds and helps reduce evaporation from the soil surface. As the weather warms, push wood mulch (decorative bark and nugget mulch) several inches from the trunk. Leaf litter and twigs are fine to leave alone. 

Perhaps this year we will have a little more time to slow down and rely less on chemical controls and more on mechanical? Hand-pick pest insects or use a steady stream of water to wash soft bodied insects off plants. Tolerate some damage, especially on ornamental plants. Those insects feed our songbirds. Use hand tools to remove weeds or till back into the soil in some areas when possible. I use chemicals, but I do it thoughtfully, using the “least toxic first” IPM method balanced with how much time I reasonably can take for a task. Straw and well composted manures work great as top or side dressing in the edible garden, where it is especially important to always be thinking of future soil health. Consider allowing a place in the garden that is less tidy to give a hiding place for birds and lizards. Be aware of where and what you spray, prune, or cultivate wherever toads, frogs, centipedes, lizards and ladybugs live. Happy April!

Unfortunately, due to the shelter-at-home guidelines, the Master Gardeners have canceled all public events until at least May 10, but our phone lines are still open: (559) 684-3325, Tuesdays and Thursdays between 9:30 and 11:30 a.m.

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