It’s a pretty simple process. The gardener needs good seed, soil, water, and sunlight (or some kind of light). Usually within a few days (typically five to 14) germination begins. Depending upon the plant, seeds should be started about four to 11 weeks before the last expected spring frost date (approximately May 1 in the Columbia Basin). One way to estimate when to set seedlings outside is to wait until night and day temperatures stay in the mid-50s. You may need to furnish additional warmth outdoors for warm weather plants until June. As gardeners, getting used to checking the temperature until summer is well upon us is important.
Commercial starting kits can be purchased to start seed at home. Use a good quality seed-starting mix, either homemade or commercial. Seed starting soil is sterile and blended to be porous, so seedlings have both moisture and light. After mixing soil with water in a large container until it is moist, fill containers to about an inch from the top, shaking the seed bed container to settle the soil.
Plant seeds about 1/4-inch deep and about an inch apart. Sift more soil onto the seed and press down firmly while watering with a fine mist. Check the plastic-topped containers daily for moisture but be careful not to over saturate. To avoid “legginess,” most plants need light as soon as they emerge from the soil and temperature from 70 to 80 degrees.
Seedlings are repotted in deeper containers when they are about 3 inches tall and have several sets of true leaves. Larger pots should be filled with pre-moistened potting soil, not the starting soil. Lift the tiny seedlings out of the germinating containers getting as much root as possible and plant a little deeper than in the original container. About once a week, begin feeding the plants with a good liquid fertilizer or fish emulsion diluted to half the normal proportions. Give the seedlings as much light as possible, rotating flats or containers.
By May 1, 50-degree days should be the norm. Before planting outdoors, plants grown in a greenhouse need to be hardened. Place the pots in a protected spot outside for part of several days. Then gradually move them to full sun, starting in the morning and then all day. Transplant in the afternoon or on a hazy day. Plant them at root level, except for tomatoes, which are sturdier if planted deeper. Firm the soil around plant and water well. They will be helped by adding an organic mulch around each plant but not touching the stem. Check the plants daily to make sure that they are consistently moist, but not saturated.
For answers to gardening questions, contact the Master Gardeners at the WSU Grant-Adams Extension office, 754-2011, Ext. 4313 or email your gardening questions to firstname.lastname@example.org. Visit our web page at grant-adams.wsu.edu.