How to Grow Tomatoes Indoors (Yes, It's Possible!)

Homegrown tomatoes—no garden necessary.

Few things compare to the taste of a vine-ripened tomato. Sure, you can get one from your local farmer's market or from a generous neighbor that likes to share their bounty. However, if you want to give tomato-growing a try but lack the outdoor space, you are in luck—it's possible to grow tomatoes indoors. Here's how to grow tomatoes indoors, step-by-step.

Why Grow Tomatoes Indoors?

Outdoor space isn't the only reason why some people can't grow tomatoes outside. "In Britain, many people choose to grow their tomatoes in greenhouses, polytunnels, or inside the house because it's warmer and protects the plants from getting blight, a fungal disease," explains Tanya Anderson, author of A Woman's Garden and founder of Lovely Greens. This is also true for many people who live in colder climates with short summers. Depending on the variety, tomatoes can take anywhere from 50 to 80 days from seed to harvest. "Growing a pot or two of cherry tomatoes in the conservatory or enclosed porch is practically a tradition, but they do well placed next to a sunny window too," says Anderson. However, do not expect a big harvest. "I would consider it just for fun, not for any substantial amount of food," says Melissa Will, founder of Empress of Dirt. Nonetheless, Will says growing tomatoes indoors is fun.

Best Tomato Varieties to Grow Indoors

Before you run out and buy pots or soil, you will need to understand the best tomato variety to grow indoors. Some varieties are better suited to containers than others. Moreover, your available space will help determine the variety to choose. Finally, the larger the tomato, the larger the pot you will need to grow them in. A 12 to 18-inch deep pot should be sufficient for most varieties, but refer to the growing information on the plant variety you pick.

If you have limited space, stick to cherry tomatoes or dwarf varieties. "Indeterminate cherry tomatoes, like my favorite Gardener's Delight, are perfect for indoor growing, as well as smaller varieties bred for outdoor containers like Tom Thumb," says Anderson. However, indeterminate varieties need support as they grow. If you are not keen on having tomato cages in the house, Will has a creative hack to keep your vining indoor tomatoes in check. "I have used Command hooks and twine to support mine as it—quite unexpectedly—grew around a large window," she explains. Anderson says that determinate tomatoes are also well-suited to grow in pots because they won't need staking or support due to their bushing growing habit.

How Much Sunlight Indoor Tomatoes Need

Tomatoes need a minimum of six hours of light per day to produce fruit, but eight or more hours of light will have the best results. Unfortunately, the quantity and quality of light are the biggest hurdles in growing tomatoes or any sun-loving plant indoors. For best results, place the potted tomatoes next to a large south-facing window. Rotate the pots often so that the plants grow evenly and do not lean toward the light. If you lack a south-facing window, you will need to supplement with artificial light. Tomatoes that use artificial light will need at least 16 hours of light per day. If you use a combination of artificial and natural light, you will have to observe how your plant behaves and adjust the amount of artificial light it receives accordingly.

The Best Soil and Watering Schedule

"Tomatoes in containers need frequent watering, especially as the plants mature and begin producing fruit," says Anderson. Although potted plants need more water on average, tomatoes do not like 'wet feet,' so good drainage is essential. Ensure the pot you use has a drainage hole and use a planting medium with good drainage. Tomatoes do best in organic-rich, loose soil that's slightly acidic. Most standard all-purpose organic container mixes will suffice.

Ideal Temperature and Humidity

Tomatoes are warm-season plants. Thankfully, most homes have temperatures that range from 65 to 80 degrees Fahrenheit. The plants do well in average humidity too. As long as your potted tomatoes are getting the right amount of light and water, the temperature and humidity in your home should not be an issue. However, keep the plants away from air vents, so it is not exposed to hot or cold drafts.

Feeding and Pollinating Indoor Tomato Plants

"Feed the plants as you would were they growing outdoors," says Anderson. Tomatoes are heavy feeders and need fertilizer, unless your potting mix already has time-release fertilizer or other nutrients. You typically fertilize at planting time, then again when the plants start to set fruit, and then every couple weeks until the end of the harvest period.

One of the downsides of growing tomatoes indoors is limited to no access to pollinators. "You may also need to hand-pollinate flowers to get fruit unless the plants are growing someplace that's open at least part of the time for insects to find their way in," says Anderson. Hand pollination is the manual transfer of pollen from the stamen (male part of the flower) to the pistil (female part). Without pollination, there will be no fruit.

Maintenance and Pests

Indoor tomato plants require the same maintenance tasks as outdoor plants. Check weekly for suckers, the small shoots that sprout out from where the stem and the branch of a tomato plant meet, and tie up vining stems as needed. Inspect regularly for pests. Your indoor tomato plants may not be susceptible to common outdoor pests like hornworms or whiteflies, but like many indoor plants, you will most likely deal with fungus gnats. Although these pests are annoying, they are harmless. "You can stop these annoying little flies by mulching the top of the potting mix with an inch of horticultural grit," suggests Anderson, "It stops the adult flies from laying eggs and the newly hatched flies from being able to get out." However, do inspect often for other indoor pests like spider mites, mealybugs, etc., and treat them with a natural insecticide.

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