Tips for Growing Tomatoes Indoors

9 Must-Know Tips for Growing Tomatoes Indoors

Skip the dull grocery store tomatoes this winter. Instead, grow your own indoor crop of salad-sized tomatoes. Tomato plants grow best outdoors, but with some special care they can grow, flower, and fruit indoors as well. A blend of art and science, growing a crop of indoor tomatoes is a labor of love. Don't expect to harvest enough to store, but expect tasty little tomatoes to add flavor to great salads, side dishes, and favorite appetizers. These 10 must-know tips for growing tomatoes indoors will help you enjoy some delicious gems that are especially welcome in the off-season.

1. Strong, bright light is essential

A collection of grow lights in the sun's place when growing indoor tomatoes. Indoor sunlight, especially in winter, is strong enough to provide the fuel a tomato plant needs to grow and produce fruit. Even bright sunlight in a south-facing window is less than what a tomato plant needs to thrive.

A simple set of grow lights or shop lights, available at garden and home centers, can be suspended a few inches above the plants to encourage vigorous growth. Place lights within 6 inches of the top of the plants. The intensity of light from the light source decreases rapidly, and light is directed away from the plant. Seedlings and young tomato plants need 18 to 22 hours of supplemental light per day when growing indoors. Plants with color and ripening fruits do not need much light and can be moved to a south-facing window.

2. Choose smaller, smaller varieties

The best tomatoes to grow indoors are varieties labeled "yard" or "bush." Specially selected as small, compact plants, these varieties thrive within the confines of a container. Traditional varieties, such as 'Celebrity' and many other heirlooms, are too large to grow successfully indoors. Expect to find patio or bush tomato varieties that produce cherry, grape, Roma, and small slicer-type fruits. Great varieties for growing indoors in containers include 'Patio Choice Yellow,' 'Tumbler,' 'Push Early Girl,' and 'Atlas.'

"Kitchen minis" are small tabletop-sized plants available at home centers and some grocery stores. These small plants are sold with fruits. Place them in a bright, sunny window and the fruit will ripen in a few weeks.

3. Provide heat for seed initiation

Accelerate indoor tomato crop germination by providing heat under seed-starting trays. Place the seed trays over a gentle heat source such as a heating mat, a radiator on low heat, or the top of the refrigerator. A few degrees of heat will start germination in a day or two. The seeds will germinate quickly and you will soon reap the fruits.

4. Transplant into a larger pot

When a tomato seedling is 6 inches tall and has several sets of leaves, transplant it into a large container filled with fresh potting mix. The container should be at least 14 inches wide. The best containers for tomato plants are at least 20 inches deep. The bigger the container, the more the roots will spread. And make sure the container has drainage holes in the bottom. Place the pot on a saucer or plate to catch excess water that drains from the drainage holes.

5. Find a constant hot spot

Tomatoes grow best indoors when temperatures are between 70 and 80 degrees Fahrenheit. Cold drafts from an open door or window can shock heat-loving tomato plants. Find a growing place protected from cold drafts. Also, note the hot air blowing from the furnace vents. Tomatoes grow best at temperatures between 70 and 80°F.

6. Keep plants moist, but not soggy

Indoor tomatoes require more regular watering than garden plants. Check the water requirement daily by touching the soil. If the soil is wet, don't water it and check again the next day. If the soil is dry, water the plant until the drainage holes are clear. Use a pot saucer or large plate to catch excess water. Empty the saucer or tray within 30 minutes of watering.

7. Fertilize properly

Tomatoes grown indoors with regular fertilization are the best fruit. Mix slow-release pelleted plant food into the potting mix at planting time and add the pellets at intervals recommended on the package. Or fertilize edible plants weekly with a water-soluble fertilizer solution. Frequent watering of container-grown tomatoes removes valuable nutrients from the potting soil; Replenish nutrients by fertilizing regularly.

8. Aid in pollination

Indoor plants need your help to ensure pollination. Tomatoes are self-pollinating, meaning they don't need pollen from another plant to set fruit. As the plants begin to bloom, gently shake them daily to mimic how the wind moves the plants growing outdoors. Gentle shaking will stimulate pollination and fruiting. An oscillating fan can produce similar results.

9. Replace plants as needed

Encourage strong, upright stems and branches by turning the plants frequently. Plants lit by overhead grow lights don't need rotation, but a tomato plant growing in a sunny window will benefit from a quarter turn every week. When not turned, plants bend toward the light.