The basis of a healthy transplant is a good soil-less potting mix. Using a soil-less mix eliminates disease organisms, pests and weed seeds that may be found in soil. I prefer organic and mix my own. There are a number of seed starting mixes available at local stores including organic mixes. You may want to experiment with various mixes or mix your own.
Basic Organic Seed Starting Mix Recipe
3 parts Sphagnum Peat Moss
1 part Perlite
1 part Vermiculite (optional)
Add per every 8 gallons of mix:
½ cup Bone Meal (Phosphorous)
1 ½ cups Dolomitic Limestone (Raises soil pH and provides calcium and magnesium)
½ cup Blood Meal (Nitrogen)½ cup Kelp Meal (Nitrogen, potassium and minerals)
Mix thoroughly and add enough water to moisten well.
Put seed starting mix in plant cells or 3 inch pots and add seed. As a general rule cover the seed with a layer of mix that is 4 times the width of the seed. Place in a sunny window, a greenhouse, or under florescent lights. Keep evenly moist. Most vegetables will grow quite nicely at temperatures between 70 and 80 degrees with 8 hours or more of sunlight or light from florescent bulbs.
Growing transplants rather than direct seeding can give you a head start on the growing season. Transplants in the garden also have an advantage over the smaller weeds that germinate around them which makes weeding easier. Planting corn at 2 week intervals will give you an extended harvest. Using corn transplants rather than direct seeding makes better use of your garden area. No space is wasted because of poor germination and seed is not lost through plant thinning. I like to grow the following plants to transplant to my garden: Onions, cabbage, lettuce, broccoli, collards, tomatoes, peppers, eggplant, cucumbers, watermelon, cantaloupe, okra, pumpkin, squash and corn.