April is another busy month for gardeners; usually a month characterized by ups and downs in temperature. Keep watch for frosts; protect cold frames with mats if frosts are imminent, and admit air daily as weather permits. Finish pruning fruit trees if not done, plant grapes; fertilize and prune blackberries. Check your fruit trees and roses for pests as soon as they bud and leaf out and set out apple pest traps two weeks before bud break. Weed and amend all your beds now while it is cool and moist.
Finish planting fruit trees, shrubs, roses, and perennials. This month is a good time to direct sow (where they are to flower)seeds of several flowers: sweet alyssum, cornflowers, carnations, pinks, poppies, stocks, rose campion, Lychnis, columbines, valerian, honesty, foxglove, snapdragons, mignonette, larkspur, kiss-me-by-the-garden-gate and four-o’clocks. Perennials still may be divided if weather has not become too warm. Violets can be divided after blooming and cuttings taken of pansies. Make cuttings of chrysanthemums, gauras, Helianthus, lupines, Lychnis, Liatris, knautias, saponarias, scutellarias and veronicas. Dahlias and tigridias may be started inside in cold climates and planted out later after frosts are over, or planted outside if the soil temperature is above 60 degrees F.
Several vegetables can be direct sown if weather permits and it is not too cold: beets, arugula, carrots, caraway, celery, chervil, chives, cilantro, dill, fennel, collards, mache, fava beans, cress, kale, Jerusalem artichokes, kohlrabi, leeks, lettuce, mustard greens, rhubarb, turnip greens, onions, pasley, parsnips, peas, potatoes, radishes, salsify, scallions, spinach and Swiss chard. Sunflowers and tomatillos can be sown two weeks before the last expected frost.
Corn may be sown after April 15th in cool maritime northwest climates, or a week or two later in the inland and mountain areas. Usually corn is sown about 10 days to two weeks before the last frost. Native Americans of the Hidatsa tribe living in the Dakotas planted sunflowers first, then corn, and after frosts followed with beans and finally, squash. Sunflowers were grown by themselves in a field, but corn, beans and squash were grown together; with corn in hills of 6-8 and beans and squash vining through.
Vegetables started last month indoors may be planted out this month: the brassicas, parsley, Asian greens, rhubarb and tomatoes; once frosts are over.
Prune established roses before bud break and seal the cuts with water-based glue or wood glue. This prevents drilling wasps from injuring the canes. Fertilize organically with Epsom salts, manure or compost, bone meal or rock phosphate, alfalfa meal and seaweed or wood ashes.
A few things maybe grafted now: grapes, hollies, pears, maples, pines and clematis. Layers can be made of Cotoneaster, Cotinus, Hydrangea, Lavandula, Lonicera and Parthenocissus.