Top 5 Tips for Growing Tomatoes Indoors (From a Tomato Expert)

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It turns out, you don’t need a backyard garden or hot and sunny climate to grow yummy tomatoes. To find out tips on growing tomatoes indoors, we turned to the tomato expert. Craig LeHoullier (better known as the Johnny Appleseed of Tomatoes for having and sharing around 5,000 tomato seed varieties) is a gardener, educator and author of “Epic Tomatoes: How to Select and Grow the Best Varieties of all Time.” He gave us the inside scoop. If you’re lucky and diligent, you can grow and eat tomatoes 12 months a year!

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Tip 1: Choose the Best Tomato Variety to Grow Indoors

First off, it is possible to grow tomatoes indoors! But you need to understand what tomato plants need to bear fruit and not just spindly vines. Choosing the right tomato is the key to success. For instance, Cherokee Purple tomatoes can grow up to 15 feet tall. That’s not going to be a happy indoor plant. To succeed with indoor tomatoes, you need short and compact tomato varieties.

LeHoullier recommends dwarf tomatoes, and starting from seed. LeHoullier says, “Micro dwarf tomatoes grow about six inches to a foot tall. You can put a seed and a little stake in a pot, and it will produce tasty little cherry tomatoes as long as it gets an adequate amount of light, food and water.”

Micro dwarf tomatoes are an ideal seed variety for growing tomatoes indoors, but you may have to search to find them. The Red Robin micro dwarf tomato is sold online, and produces a surprising number of fruits for its 12-inch stature. The secret to a micro dwarf tomato is the small size of the fruit, and the plant itself stays short—ideal for growing in a window and in a small pot. LeHoullier explains that micro dwarf tomatoes can be yellow, orange, purple or green or red. Fun!

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Tip 2: Pick your Pot and Place for Growing Indoor Tomatoes

For indoor tomato success, you need sun and heat which is best provided indoors with southern-facing windows. Tomatoes need the photosynthesis to develop flavor and flowers that turn to fruit. If the conditions are too cool, the tomato plant will grow slowly and get leggy without producing many tomatoes. You could invest in some LED grow lights if you live in exceptionally cold climate and don’t have southern exposure windows.

For potting indoor tomatoes, LeHoullier states that any pot will work, but it must have a drainage hole at the bottom and a saucer underneath to catch the water. He says, “You can use terra cotta containers, but they leach water through the sides. Don’t use pots that break down over time; your plant will fall apart on the windowsill.”

Psst—learn what happened when our editor tried an AeroGarden to grow herbs indoors.

Tip 3: Choose Good Quality Potting Soil and Overwater Indoor Tomatoes

When it comes down to planting tomato seeds, you need good quality and sterile potting mix. Something like MiracleGro indoor potting mix starts off sterile, so you’re not introducing possible diseases into the plant. Just like with any houseplant, you can get different pests in your indoor tomatoes. Watch for aphids and whitefly especially with indoor tomatoes.

For feeding indoor tomato plants, LeHoullier recommends a half strength all-purpose fertilizer at about a quarter cup per plant per week. Regular feeding will keep the plants producing flowers, which means producing tomatoes.

How about watering indoor tomatoes? According to LeHoullier, “Always overwater a little bit. The pot should have drainage at the bottom. You can’t really overwater but tomatoes are unhappy if they’re underwatered.”

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Tip 4: Rotate the Indoor Tomatoes

Tomato plants tend to bend towards the light, which is a problem when growing tomatoes indoors. To prevent leggy, bent plants, turn them 90 degrees every day to help them grow as upright as possible. LeHoullier recommends adding a 10-inch plant stake to the vine, especially once it starts to bear fruit. The heaviness of the tomatoes can make the vine fall.

If you do have outdoor space, even as small as a fire escape or patio, putting the plants outdoors in the warmer months can help keep them strong through the fall when you bring them back indoors. “When it’s starting to get to frost, you can bring them in and keep them going indoors,” LeHoullier explains.

Tip 5: Eat your Indoor Tomatoes!

With a little bit of luck and healthy plants, you can enjoy indoor tomatoes all year-round. After a tomato plant produces flowers, you should have fruit in about three weeks. And if it’s not going as fast as you hoped? Don’t worry. LeHoullier has grown over 4,000 types of tomatoes in 40 years and he says, “Don’t take it too seriously. I make mistakes every year!”

Next, check out fast-growing vegetables you can harvest quickly.