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Growing Tomatoes Indoors: Year-Round Fruit

Growing tomatoes indoors may seem like an impossible feat for this heat-loving fruit, but indoor tomato plants are easy to grow. Provide the right setting for your plant, and you’ll have tomatoes indoors all year long. Then enjoy the fruit of your labor every day. 

Growing indoor tomatoes takes the same skills as outdoor tomato plants, but there’s the benefit of elemental control. There are few pests to deal with indoors, and very few environmental conditions that ruin your crop. There are even dwarf tomato varieties that don’t get out of control, as both dwarf indeterminate tomato plants and determinates exist. 

Some people don’t have the space for outdoor growing, which makes growing indoor tomatoes a much better option. People of varying mobilities and abilities can enjoy watching their plants grow and fruit all season long, even in winter.  If you’d like to learn how to produce tomatoes in your house, read on! It’s not hard to accomplish. 

Cherry tomatoes produce well indoors, even in winter. Dwarf varieties like Tiny Tim are excellent because they grow no more than two feet tall. Dwarf tomatoes grow from summer to winter indoors. You can save the seed inside the fruit to grow again next year. Check out the different types of tomatoes suited for indoor growing in any major seed catalog. Alternately, collect cherry tomato seed from the fruit themselves for later germination. 

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Methods For Growing Tomatoes Indoors

Growing tomatoes indoors
Growing tomatoes indoors can provide you with winter produce. Source: Colin-47

There are multiple ways to grow tomatoes indoors. Perhaps you have window space where cherry tomatoes get adequate sunlight. Since tomatoes love UV rays, this is an excellent way to grow them. An indoor window keeps your plants out of the cold and provides tomatoes with the hours of direct light they need per day. 

Note that in a window there won’t be bees to pollinate your plant. Depending on the method of tomato care, your setup may take up a lot of space. You may also need to supplement with a grow light. As long as there is enough direct light, you’ll have a great harvest to draw from. 

It helps to grow tomatoes indoors under a T5 fluorescent grow light if direct sunlight from a sunny window isn’t an option. Remember, grow lights may slightly increase utility bills. Still, they may be the best option for some who have no other way of growing indoors. 

Grow tents are another excellent option for growing inside. They accommodate a large plant if you prefer to maintain a regular-sized determinate tomato plant. They also provide precise controls for light and humidity, which makes achieving optimal conditions possible. They can also take up a lot of energy and space, though. So consider this before you purchase a grow tent. 

Hydroponic setups are great for tomatoes you grow indoors, too. Because they grow in a water-based nutrient solution, they’ll be juicy and delicious. Advances in home-growing technology have made it so there are plenty of hydroponic options to choose from in many different sizes and formats. You can have a setup that takes up a kitchen counter or a baker’s rack. You could also grow tomatoes in a hydroponic tower. 

The only downfall to growing regular or cherry tomatoes hydroponically is higher energy costs. This method also takes a lot of management skills that some may be too busy to tackle. But keep it up and you’ll have winter tomatoes for sauces that stew all day.  

Caring For Indoor Tomatoes

Baby tomato plants
Once germinated, separate or thin your tomato sprouts, keeping the strongest. Source: Ramsay2

Whatever method you choose, there are basic requirements needed to grow fruit that is viable, juicy, and delicious. Maintain those and you’ll have tomatoes year-round. 

Lighting & Temperature

Tomatoes are a full sun plant and need at least 6 to 8 hours of direct sunlight per day. A south-facing window in the northern hemisphere or one that faces north in the southern hemisphere is great for these light stipulations. If your windows are next to obstructions that block out light, try one of the other methods listed here. 

T5 grow lights supplement sunlight in a window with obstructions throughout the day. Provide your window plant with one of these to mimic additional sun exposure. A hydroponic setup might come with lights, but if you’re developing your own system for growing tomatoes indoors, use one of these. 

The ideal climate for a tomato plant is in the 70 to 85-degree range. So keep tomato plants away from vents that could alter the temperature too much. A cold stream of AC could stunt the growth you’ve worked for. Dry conditions from a heat vent damages plants too. If there is no escaping your HVAC system, close the nearest vent or use a grow tent to keep the temperature and humidity stable. 

Consistently rotate your tomato plants to help them establish healthy roots and grow evenly. Outdoors, tomato plants get the full spectrum of sunlight, so you need to simulate that indoors by rotating the planter. 

Water & Humidity

In hydroponics, water will always be available to your indoor tomatoes as needed. Change the solution at least once per week to keep things fresh and bacteria-free.  

Container-grown tomato plants need at least one inch of water per week and good drainage. Different pots and growing mediums have different water retention capabilities. Maintain consistently even moisture for best results.

Some pots come with a draining tray to set your plant in. It’s generally best to empty out the tray when it fills with water to prevent waterlogging your growing media.

Growing Medium & Container

If you grow tomatoes indoors in soil, make sure the blend you’ve chosen is rich, loose, and well-draining. A soilless potting mix works well for tomato growing. Coir starter pellets or a mix of vermiculite, sand, and coir will do the trick. Remember though that a soilless medium will require fertilizing as it lacks most nutrients. In hydroponic systems, clay balls are an excellent growing medium. They aren’t great for the other methods listed here though. 

Tomatoes need a lot of depth to grow. Even dwarf varieties need deep planting. Therefore, your pot should be at least 5 gallons for dwarf tomatoes, and at least 10 gallons for regular varieties. Pots need drainage holes. Self-watering pots aren’t great for tomatoes that are sensitive to overwatering or inconsistent applications of water. Grow bags are good, but they are porous. If you have a way to catch the water that will flow out of the grow bag they’ll work. If not, stick to a large clay or plastic planter. 

Fertilizing

Even though your potting media might be rich with compost, you’ll need to fertilize tomatoes. Tomatoes in the garden and indoors need fertilizer. Apply a tomato-specific slow-release fertilizer to your potting mix or soil-less growing medium at planting time. Supplement every couple of weeks by adding more in a ring around the plant and watering in. Many suppliers sell powdered tomato nutrients for hydroponics that offer the same benefit that soil fertilizers do. For indoor tomatoes in a hydroponic setup, dissolve some powder in water, and add at planting time and then once every two weeks. 

Pruning

Tomato stem
Remove leaves from low on the stem. Source: tom_bullock

As they grow their first flowers, pinch them off to encourage plant growth, keeping flowering for later when the plant has grown enough to handle the weight of fruit. Remove the bottom leaves of your tomato plants as they grow to about six inches tall to prevent splashback from the media onto the plants.

Indeterminate dwarf tomatoes are wilder than determinate plants. As needed, prune branches just above the node to shape your plant. Both determinate and indeterminate tomatoes grow suckers and can benefit from having those removed. If you enjoy growing indoor tomatoes, you may place suckers in prepared soil or potting mix to root them and propagate seedlings. 

Planting

To start your indoor tomatoes from seed use starter trays and a heating mat. Sow your tomato seeds at about 1/8th of an inch deep and cover the pots or trays with plastic wrap to trap in heat and moisture. Use a starting mix of equal parts of vermiculite, perlite, and coir, or alternately use a commercial seed starting mix. The seed itself can support its nutrient needs through germination. Warm the heating mat gently at 60 to 70 degrees, the optimal range for tomato germination. Keep them warm and remove the plastic when the seeds germinate. In one to two weeks, you’ll have a tomato seedling. As it matures, transplant it into a larger pot as needed.

For hydroponics, start seeds in coir pods and keep them warm on a heating mat. In one to two weeks transplant your seedlings into the system with fresh nutrient solution. In both hydroponic and non-hydroponic settings, do not overcrowd tomato seedlings. Even when you grow tomatoes indoors, provide proper spacing. Most tomato plants will take up one 5 gallon planter. If tomatoes get overcrowded, they can’t take in enough light and nutrients to form flowers. This stunts fruit development, too. 

Troubleshooting

Tomato flowers
You will need to pollinate your own tomato flowers indoors. Source: monteregina

When you grow tomatoes indoors, you won’t have as many pests and diseases to deal with compared to outdoor tomatoes. Let’s cover the issues you could face when growing an indoor tomato garden. 

Irregular watering can cause aberrations like split fruit. Just as growing outdoors, when you’re growing indoor tomatoes provide adequate, regular water. Hydroponic tomatoes have less of an issue here due to a consistent supply of water. 

Too much water speeds fungal and mold growth. This can result in root rot, which can kill your plants. In general, overwatering itself can be a problem, too. Avoid overwatering, and provide water only when needed. 

Poor nutrient uptake can happen when you’re growing indoor tomatoes. Water flushes nutrients out of the pot before your plant absorbs them. Keep on a fertilizing schedule throughout the season. When you grow tomatoes indoors regular fertilization is key. This is one of the main components that help your plants produce fruit you’ll harvest even in winter. This can prevent nutrient deficiencies like blossom end rot. 

When you grow tomatoes indoors you don’t have extra help from pollinators who provide a boost to fruit production. Help your plant pollinate itself with a cotton swab after flowers bloom. Touch the tip of the swab on each open flower to collect and spread pollen. This transfers pollen from one flower to another, helping your plant produce more fruit than it would otherwise. You’ll have more to harvest this way. 

Garden tomatoes and indoor tomatoes are sensitive to cold damage. In winter, a window might get too cold and may lack the proper amount of sun needed for healthy green growth. To help your plant through the cold seasons, provide a grow light. With the heat and light from a T5 fluorescent bulb, you’ll have lush green leaves and your plants will produce through the winter season and into summer. If it’s not quite warm enough, placing your plant on a seedling heating mat may help.

Alternatively, too much sun or too many hours of warm weather above 90 degrees causes blossom drop and singing on the green leaves of your tomato plant. Make sure your lights are on for the appropriate amount of time (especially in summer months when it’s hot) and monitor the temperature around the plant you grow indoors. Keep it in the 75 to 85-degree range as much as possible. 

Two pests can travel from outside, especially in the summer, and get into your plants. These are fungus gnats and broad mites. There are a variety of organic pesticides available help to reduce gnat and mite damage from occurring in each pot in your indoor garden. 

Frequently Asked Questions

Tomato seedling
Your seedlings should be transplanted into a pot that can support their root mass. Source: Airflore

Q: Can tomatoes be grown indoors?

A: Absolutely! With the right care and conditions growing indoor tomatoes is not only possible but rewarding. Grow them indoors and have fruit all season long. 

Q: How long can a tomato plant live indoors?

A: Without interference from pests and extreme environmental conditions, you’ll grow tomatoes indoors for over a year.


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