What to do in your garden in April
• Bedding plants. Replace fading cool-season annualswith heat lovers such as celosia, dahlias, marigolds, petunias,salvia, verbena, and vinca. Try starting cosmos, sunflower, andzinnia from seed, even if you're a novice gardener. They're allsuper-easy, make good cut flowers, and attract the beneficialinsects you want in the garden.
• Rose companions. Planting perennials in your rosebeds adds complementary textures, forms, and colors, and providesinterest when roses are not in bloom. According to Wen Wang,rosarian at Descanso Gardens in Flintridge, good choices includecatmint, cranesbill, feverfew, French lavender, lamb's ear, Shastadaisies, snow-in-summer, and veronica. We also like bearded iris,scented geraniums, and 'Indigo Spires' salvia.
• Roses. Container-grown roses are in full bloom andin plentiful supply at nurseries this month. Three outstandingnewcomers ― all floribundas ― are worth seeking out:'Julia Child', a delicious butter yellow; smoky purple,clove-scented 'Ebb Tide'; and 'Tuscan Sun', a deep apricotblend.
• Vegetables. Coastal gardeners (in Sunset climate zones 21-24) can continue to plantquick-maturing, cool-season crops, including chard, leaf lettuces,radishes, and spinach. Inland (zones 18-21), switch to warm-seasoncrops such as beans, corn, cucumber, eggplant, melons, peppers,summer and winter squash, and tomatoes. In the high desert (zone11), wait a few more weeks; frost is still a possibility.
• Divide cymbidiums. If pots are too packed withbulbs, some brown and leafless, it's time to repot. Knock the rootmass out of the pot and separate it into clumps by hand or withpruning shears. Keep at least three healthy bulbs with foliage;repot those in fresh potting medium designed for orchids.
• Fertilize. Feed trees, shrubs, groundcover,perennials, and other permanent plants. Try using a fertilizercontaining iron on all plants, not just the chlorotic ones. That's Steve andDonna Brigham's practice at Buena Creek Gardens nursery in SanMarcos. They use Best Super Iron (9-9-9 with 11 percent iron) tolower pH and brighten flower colors. Apply at half strength andwater well after application.
PESTS AND DISEASES
• Combat powdery mildew. Warm days and cool nights areideal conditions for powdery mildew. Prevent this fungus by hosingoff foliage in the morning several times a week to wash off spores.To treat it, spray foliage with a baking-soda formula, such as 1tablespoon baking soda plus 1 tablespoon canola oil to a gallon ofwater.
• Manage aphids. Keep the aphid population in controlby stripping the pests from plants by hand. Wear thin disposablerubber gloves. Or dislodge the pests from plant foliage with astrong blast of water from a hose.
• Manage snails. Search for snails on strappy-leafedplants such as agapanthus and daylilies, then hand-harvest anddispose. Or trap by allowing them to collect on the underside of aslightly elevated board.