Some people say planning one’s own vegetable garden is too much work, but others like the satisfaction of growing their own plants instead of buying vegetable transplants. Once you have developed your plan for this summer’s vegetable garden, the next step is to the make decisions on what vegetable plants to start indoors.
Timing: Gardeners generally tend to start transplants far too early. The resulting plants outgrow the cell pack container, and plants become pot-bound and exhibit tops that are spindly and weak due to crowded competition for light.
Most vegetable transplants, except the cucurbit family (cucumbers, cantaloupes, squash and watermelons), need six to seven weeks from seeding until the plants are ready to set out in the garden. Cucurbits will require only three weeks. It’s not difficult to calculate the proper time to start seeds. For example, if it’s safe to set out tomato plants in about June 1, then tomato seeds should be sown indoors about mid April. Broccoli is a cool-season crop and would be set out in the garden between April 1 and 15, so they would be sown indoors about mid March.
Soil mix: Gardeners often try to sterilize their topsoil to produce vegetable transplants. It’s fun to be a do-it-yourselfer, using only homegrown resources including garden soil, but the commercially prepared “artificial soils” consisting of peat moss, vermiculite, perlite and pine bark are lightweight, free from plant pests and soil-borne diseases, and drain very well. They are far superior in performance compared to garden soil.
Light intensity: Producing homegrown vegetable transplants can result in poor transplants because of poor light. Unless you have a solar room with overhead sunlight or a greenhouse, chances are your windowsill light, except for brief periods on sunny days, is too shady. Indoor gardeners will need fluorescent lights placed about 12 inches above the seedling tray. The lights should be on a timer to provide 16 hours of bright light for each 24-hour period. Dual fluorescent tubes, one cool-white and one warm-white, provide an excellent balance of usable light for photosynthesis. As plants sprout and grow under lights, the tubes should be raised so as not to produce too much heat near the tops of the plants.
Temperature: Fluorescent tubes emit a lot of warmth, so keep plants growing on the cool side to promote stocky versus succulent growth. For best results, turn off or turn down the heat to 55 degrees in the room where your plants are started. A cool basement is an excellent area for starting plants under lights. Temperature requirements for germination are quite different from “growing on” temperatures. A temperature of 80 degrees is good for germination, and 60 degrees is preferable for growing most vegetable transplants to keep them stocky and healthy.
Growing tips: Containers can be covered with plastic, clear glass, plastic wrap or waxed paper until seedlings begin to sprout to keep in warmth and moisture. Another fluorescent tube or a small lamp with a 75-watt incandescent light bulb placed directly under the shelf supporting the flats provides perfect bottom heat. This heat source should be turned off as soon as seeds begin to pop up. If not, seedlings will stretch from too much bottom heat.
When plants are about 4 inches tall, as opposed to plants that are 10 to 12 inches tall, they are an excellent size for the least transplanting shock and for faster regrowth in the garden. When your plants have reached 4 inches in height and are well branched and stocky, they should be “hardened off” by reducing watering frequency and moving plants to an outdoor porch or coldframe for the final week before going into the garden. This will toughen them to the effects of wind and outside temperatures, and to the natural light/dark cycle. If an unexpected frost is forecast, move the plants back indoors under 16 hours of light, but keep the temperature at 55 to 60 degrees if possible.