Growing plants from seed is an economical way to get a jump on the gardening season. Homemade greenhouses provide a warm, moist environment that encourages seeds to sprout and gain strength. If your gardening space is limited, be creative and make your own greenhouses from plastic tubs or old pans.
Plant annual flower and vegetable seeds in the containers you'll raise them in. The Royal Horticultural Society's "Essential Gardening Techniques" recommends scattering seeds thinly and evenly over potting compost and covering the seeds with a fine layer of compost.
Mix fungicide into your watering can and water gently. Cover the container with a pane of glass, rigid transparent plastic, a plastic bag or cling wrap. Leave the container in a warm place until seedlings emerge. Use the tops of refrigerators or freezers for warmth or place pots in a warm airing cupboard.
Once seedlings appear, remove the glass and place the pot in a well-lit place. Harden off young plants in a cold frame before setting your pots outside on a full-time basis.
Plant larger quantities of seed in metal, glass or ceramic baking dishes or disposable plastic salad trays. Use cake pans, roasting dishes or cookie sheets with tall sides to hold the soil. Spread a layer of planting compost over the bottom of the dish, roughly one-half-inch thick. Spread seed over the compost at the spacing intervals noted on the seed packet and cover with compost to the recommended depth.
Place in a warm location until seedlings emerge and then move them to a lighted spot. The Natural Resources Conservation Service recommends that once seedlings have developed two true leaves, you should transplant them. Gently tap the side of the container to loosen the compost and use a plant label or dibber to work the seedlings loose. Transplant the seedlings to peat pots and keep them moist and in lighted conditions. When firmly established, harden off young plants before planting.
Peat Pellet Greenhouses
Raising seedlings in peat pellets avoids root disturbance after plants emerge and before you plant them in your garden. Peat pellets are usually purchased in dehydrated form. Add water and allow them to expand to their full volume. Plant seeds as directed on the seed packet directly into the pellet, and place them in a shallow baking dish or plastic salad tray. Cover the tray with plastic wrap or a pane of glass and leave in a warm place until seedlings emerge.
Remove the cover and place the tray in a lighted spot. When seedlings develop two true leaves, plant the peat pellet in a larger peat pot. Keep the pots moist and in a lighted location until your young plants are firmly established. Harden off in a cold frame before planting the entire peat pot in the garden.