Growing Tomatoes Indoors: Top Tips for a Bountiful Winter Harvest

Aphids and Spider Mites on Indoor Tomato Plants

Aphids and spider mites will wreak havoc on indoor plants. They are two of the biggest issues that you’ll encounter while trying to grow your tomato plants; you may find yourself struggling to keep them alive. Both insects feed on the tomato plants, with infestations ultimately killing them. Without fluctuating weather patterns, beneficial insects, and other ideal hosts, both insects will be hard to keep at bay.

Try a twice weekly regimen of spraying your plants, and always treat every plant in the room. Be very careful with insecticidal sprays, though; avoid using them indoors. Instead, spray your plants with water, with a drop or two of dish soap added. In nature, the rains are quick to sweep away spider mites, while ladybugs swoop in to gobble up both aphids and spider mites. When growing tomatoes indoors, you simply don’t have this protection.

Lack of Warmth Stunts Growth

Tomatoes are a warm-season crop. Without adequate heat, the plants will not grow well. They will sit in a state of semi-dormancy; they won’t grow, they won’t flower much, and they rarely fruit. However, ideal fruit set is achieved when you reach into the 70’s; if your plants are in an area that frequently dips into the 40’s or 50’s, you should provide supplemental heat.

Pollination Problems Reduce Fruit Set

Outside, you’ll have bees, birds, wasps, and other small insects that’ll pollinate your plants; even the wind! Indoors, you’re going to have to hand pollinate all flowers for the best rate of fruit set. Tomatoes generally don’t require pollination, but it is highly recommended indoors. You can pollinate your tomatoes in two ways:

  • Use a paintbrush to dab each individual flower, disturbing the pollen, or
  • Shake the plant gently but quickly, to mimic the wind and jar the pollen

No Wind Means Weaker Plants

Believe it or not, the wind is a critical component in keeping tomato plants strong and sturdy. Indoors, tomatoes plants have no resistance to compete with. Thus, the plants will overall be more weak. This could result in broken branches under weight, and the plants may be prone to significant damage if they are transplanted outdoors, where the wind might snap them.

Outdoors, the wind pushes and pulls the plants, encouraging a stronger, sturdier, more resilient stem. This plays a part in keeping the plant more upright and rigid under a heavy fruit set.

To fix this problem, place a fan in front of your plants posthaste. Keep it running fairly often. This will help the plants to build strength, reducing the risk of broken branches, falling fruit, and failing plants.

Watch Your Watering Carefully

Indoor conditions, especially during winter, can be conducive to mold growth. Fungal infections will run rampant if the soil is kept too moist. Allow the soil to dry out between waterings, which helps to reduce the risk of disease. If you see mold growing, then your plants are likely too wet. If your home has very low humidity during winter, it’s also possible for the soil to dry out quickly. Stick your finger 1″ into the soil; if dry, proceed with watering.

Stopping Fungal Tomato Infections in Their Tracks

One of the best ways to fight fungal infections is with a fungicide. I don’t recommend spraying anything indoors, so be sure to spray plants on a sunny, warm winter day. You can also:

  • Expose pots to sunlight (most fungi don’t enjoy sunlight)
  • Keep pots on the dry side
  • Use a diluted hydrogen peroxide spray to eliminate fungus
  • Isolate infected plants to prevent the spread of disease

Some varieties are more resistant to diseases than others, so if you have previously lost an indoor garden to a particular disease, I encourage you to opt for varieties that have resistance to those diseases.

Fungal spores can remain dormant for years, and they may hide out in carpeting, upholstery, drapes, or any other porous surface until they are stirred up again.

Which Tomato Varieties Are Best for Growing Inside?

For indoor tomato plants, I highly recommend micro tomato plants and cherry tomato plants. The last thing you want is a beefsteak tomato plant growing in your family room; with vines up to 12′, you’ll quickly lose most of your living space, likely with no tomatoes to show for it. You can find our tomato seed buying guide here, for a massive list of different uses/conditions and the varieties most suited for those situations.

Micro tomato plants only reach 6″ to 24″ tall. This makes them easy to grow on a window sill, counter, or table, and it’s even easier to keep supplemental light on a smaller plant. They’ll produce a small amount of tomatoes for snacking, salads, or even cooking, if you grow several plants.

Micro Tom Tomato Plant

Reaching 6″ to 8″ tall, this is the tiniest tomato plant that you can get! This is the most ideal option for a counter top tomato plant, which can easily and comfortably sit in a window sill. It produces small, 1 ounce fruits, which are perfect for salads and snacking.

Minibel Tomato Plant

These plants are supposed to reach roughly 12″ in height, but some report growth up to 24″ in height. This is a highly productive micro plant that produces cherry to plum sized fruit; while it’s advertised as requiring no support, it seems that production is heavy enough to warrant support. If you have an overachiever on your hands, I’d recommend supporting the plant.

Red Robin Tomato Plant

Expect these tiny troopers to reach 8″ to 18″ in size! They perform quite well indoors, and if taken care of properly, will provide you with tomatoes for several years. They produce cherry sized tomatoes, but are not sweet tomatoes. This plant will require some light support as it begins to pump out lots of tiny red tomatoes.

Tiny Tim Tomato Plant

With 3/4″ to 1″ sized cherry tomatoes, this little 12″ tall plant is also an excellent option for growing inside. Maturity is marked as 45 days, which is an incredibly short period of time for a tomato plant. Again, staking may be quite helpful in keeping this little plant upright, so that it doesn’t fall beneath the weight of its own fruit.

Pinocchio Micro Dwarf Tomato Plant

Pinocchio is the only yellow micro variety that I’ve listed here; with yellow tomatoes being the sweeter class, this is the perfect option for those who prefer a sweet snacking tomato. This plant will reach heights of 7″ to 12″, while also being indeterminate. This means that you could root the suckers that it sends out, producing even more tomato plants!

Rosy Finch Micro Tomato Plant

This plant produces beautiful, rosy fruits. They will reach roughly 10″ in height, and perform quite well in containers that are 1 gallon in size (or smaller, if you provide adequate nutrients!) They have a mild flavor, and are somewhat sweet. Fruits are not overly seedy, either.