Even if you live in an apartment or home that lacks outdoor gardening space, you can grow tomato plants indoors if you have a sunny window. Growing tomatoes indoors can be challenging, but the sweet rewards are well worth the efforts. The key is ensuring the plants have enough of all the vital elements they would need outdoors: light, water, nutrients, and space.
Purchase a determinate tomato variety that only reaches 3-4 feet, rather than indeterminate which continue growing through the season and can reach up to 10 feet tall. Select a hybrid variety that produces smaller fruits, such as cherry or plum tomatoes.
Get a container that is a minimum of 14 to 16 inches deep, and 14 to 16 inches wide. If you have room, use a larger pot. Cramped roots will reduce yields. Be sure your pot has a drip tray.
Transplant your seedlings into your pots using potting soil enriched with compost. Mix a lightweight medium to make your planters easy to move with one part potting soil, one part compost, one part peat moss and one part perlite.
Place a tomato cage into the pot at the time of transplanting to give the plant support as it grows. Add mulch around the base of the plant to help retain moisture.
Set your plants in a window that gets at least 6-8 hours of direct sunlight, or more if possible. Ideally the window should face south or southwest.
Rotate your tomato plant 1/4 turn every day so that each side gets an even amount of light.
Supplement with fluorescent lights a few hours each day if your plant is not getting at least eight hours of direct sunlight.
Water your tomato plant deeply at least twice per week, or whenever necessary. Don't allow the soil to dry out. It should be damp, but not soggy.
Avoid watering the foliage, which can make the plant more susceptible to diseases. Keep the leaves and fruits dry, and just water the soil.
Tap the stems and branches when plants bloom to aid pollination. The vibration will help pollination. Indoor tomatoes require help with pollination because they lack the outdoor agents such as wind and bees.
Fertilize more frequently when growing tomatoes in pots indoors. Use an all purpose water soluble fertilizer or tea made from compost every three weeks.
Harvest tomatoes when they reach the size of maturity, but are still green. Place fruits on a windowsill to finish ripening.