Many people plant tomato seedlings purchased from a nursery directly into the garden. By growing your tomatoes from seed, started indoors, you know more about the plant and can guarantee that your tomatoes have been organically grown (something you can't always be sure of with nursery grown plants). Starting tomato plants from seeds is less expensive than purchasing seedlings and it is easy to do.
Plant tomato seeds indoors in individual 3-inch pots, eight to 10 weeks before your last spring frost date. Use a nitrogen- and humus-rich growth medium, containing equal parts peat moss and sterile compost (sterile compost can be purchased or made at home by baking at 180 degrees for 30 minutes). Sow two or three seeds per pot.
Water with compost tea or fish emulsion. Make compost tea by placing one quart of compost in a cloth bag and steeping in a gallon of water for several days. Stir or aerate to activate beneficial microorganisms that help plants take in nutrients.
Clip all but the strongest in each pot when seedlings have developed four to six leaves. It may be difficult to remove healthy seedlings, but the ones left to survive will benefit from having plenty of space to grow.
Place seedlings in a sunny windowsill or where they will receive bright light. Tomatoes thrive in full sun in the garden and seedlings love it, too. Turn pots in windowsill each day to avoid leggy plants.
Harden off before transplanting in the garden. Hardening off is a process to acclimatize seedlings that have been indoors to get them accustomed to outside conditions before placing them in the garden. This is accomplished by setting plants out on a patio or other protected outdoor area for a few hours each day, for about a week prior to planting.
Plant seedlings 4 feet apart in the garden two weeks after the last spring frost in soil warmed to 60 degrees Fahrenheit. Black or clear plastic can be used to draw heat and warm soil in colder areas. Fill holes with 4 inches of compost before setting in seedlings to give them a good, healthy start.