What to do in your garden in April
Annuals. Replace fading cool-season annuals with heatlovers. Zinnia Profusion is a favorite with Sunset's Garden staff because of its six months of bloom.Besides Cherry, Orange, and White, this year Profusion is availablein Apricot and Fire (scarlet-orange). Other popular choices includeageratum, coleus, dahlias, marigolds, nicotiana, and phlox.
Container-grown roses. Buying roses in bloom is moreexpensive than bare-root, but it allows you to judge flower color,form, and fragrance. Nurseries are well-stocked withcontainer-grown plants this month.
Dahlias and gladiolus. Coastal ( Sunset climate zones 22-24), inland (zones 18-21), andlow-desert (zone 13) gardeners can plant dahlias now. In the highdesert (zone 11), begin planting gladiolus. Want more choices thanyour nursery offers? Try www.easytogrowbulbs.com,a new mail-order source that specializes in bulbs for warmclimates.
Vegetables. Coastal gardeners (zones 21-24) can continue toplant quick-maturing, cool-season crops like chard, leaf lettuces,and spinach. Inland (zones 18-21), switch to warm-season crops likebeans, corn, cucumbers, eggplant, melons, peppers, pumpkins,squash, and tomatoes. In the high desert (zone 11), frost is stilla possibility; wait a few more weeks. If you're looking for a seedsource for Thai, Japanese, or other unusual eggplant, try BakerCreek Heirloom Seeds (www.rareseeds.com or417/924-8917). It sells more than 30 eggplant varieties.
Fertilize. Feed trees, shrubs, groundcovers, perennials,turf grasses, and other permanent ornamentals (as well ashouseplants) that didn't get fertilizer last month.
Prune euphorbias. To keep E. characias and other commonly grown euphorbias fromgetting leggy, cut them back hard after their chartreuse bloomsfade, suggests garden guru Mary McBride of Mary's Garden nursery inVista. Plants will generate fresh foliage.
Treat for iron deficiency. If camellias, citrus, hibiscus,and other plants exhibit yellowing leaves with green veins at thistime of year, it's a sign of iron deficiency. Feed plants with afertilizer containing chelated iron.
Pests and Diseases
Powdery mildew. A common problem on rose foliage and othersusceptible plants in spring, especially along the coast, thisfungal disease can be difficult to manage. Control it by sprayingleaves with a baking-soda formula: Add 1 tablespoon baking soda and1 tablespoon canola oil to 1 gallon of water.
Rose pests. Rose slugs ― those caterpillar-like insectlarvae that chomp and tatter rose leaves ― have been a hugeproblem in recent years, especially for coastal gardeners. Organicinsecticidal sprays have little effect. Chemical pesticides likeSevin work, but they kill beneficial insects too. A new option isSpinosad, a pesticide derived from a soil bacterium. Rose slugsingest it, which causes them to stop eating, then starve. Spinosad,the active ingredient in Monterey Garden Insect Spray (availablefrom www.montereylawngarden.comor 559/499-2100), does not harm most beneficial insects.