northern gardeners should use grow lights 14 to 18 hours a day
If the plants have been inside a greenhouse, harden them off over a period of two weeks. Begin by leaving plants outside for just a couple of hours a day then gradually increase the length of time they spend outside, avoiding windy days
sunniest spot with at least 7 hours of direct sunshine a day. For tomatoes, sunshine is like water and they’ll soak it up and produce more fruit!
make sure your tomatoes aren’t too crowded so the sunshine can reach their lower leaves. Plant seedlings (small plant) 30 to 48 inches apart, with rows set 48 inches apart.
soil temperature must be consistently over 60 to 65 degrees Fahrenheit. Warm the soil with plastic a couple of weeks before you intend to plant.
plant a little deeper than they come in the pot, all the way up to the top few leaves
add a blanket of mulch! It helps to conserve moisture
After your tomato plants reach about 3 feet tall, remove the oldest leaves from the bottom foot of the stem
pinch and remove some of the suckers that form between the main stalk and the side branches (They won’t bear fruit and will take energy away from the rest of the plant.)
water deeply, 1 to 2 inches of water per week
Some gardeners like to feed their tomatoes compost tea. Soak one part organic compost in one part water, let sit for 24 hours, filter the “tea,” and use to nourish plants.
Companion planting: tomatoes seem to thrive when planted with basil, basil and marigolds act as a natural insect repellent when planted amongst tomatoes, helping to ward off whitefly. Borage (starflower) attracts bees and tiny pest-eating wasps, making it a great companion for tomatoes.