Growing Hydroponic Indoor Tomatoes

Fresh tomatoes are far superior to the schlock you get at a grocery store. They taste sweet and fill your senses with a deep flavor that only comes from picking the fruit after it fully ripens on the vine. Problem is that when you grow outdoors, you’re going to get roughly 6 billion tomatoes from August to October and then nothing. We can fix that by growing indoor tomatoes.

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Easy, hydroponic, indoor tomatoes

You can certainly grow those large, succulent, heirloom varieties indoor, but it takes commitment, space, and fairly large grow lights to get a useful harvest. Greenhouses do this all the time and get fantastic results. However, it’s a better to start with something small. Like, really small.

What you need

  • Seeds or a starter plant – I’ve been using this Tiny Tim variety which makes tasty tomatoes and hearty plants at that. It seems to be a little prone to root rot, so stay on top of that. I use Hydroguard to protect against it, but keeping things clean and occasional use of hydrogen peroxide would probably be sufficient. You can check out our Seed Starting article if you need a refresher on how to start a plant from seed.
  • A place to grow – you need about a 1’x1′ area and 2′ of height. Reflective walls are all nice and good, but not necessary.
  • A grow light of about 15-30W (LED), or a sunny windows sill.
  • Something to grow in – I’m going to go with a Kratky setup for this. The best containers I’ve found for this are 2qt paint mixing buckets with lids. You can use pretty much any half gallon on more container as long as it can be cleaned easily.
  • Something to hold your plants – You can get some 1-inch rock wool squares, which are self contained, but you’ll be lifting the lid to peek in under the plant from for inspecting the roots. I tend to use 3″ net cups and peat pucks. They come out easily and the net cups are re-usable.
  • Fertilizer Masterblend is the gold standard, designed for tomatoes, and cheap. So, if you plan to grow a bunch (and this fertilizer is a great all-purpose one), go right ahead and buy some. That said, if you want to try this and don’t necessarily want to purchase 2500 grams of fertilizer on a recipe that needs about 5g/gallon, we can find other options. One pound of Veg+Bloom is not terribly expensive and is the one I started with on my grows.

Growing your hydroponic indoor tomatoes

Let’s start this grow!

Prepare your container.

  • Black out the sides so light can’t get in, but leave a visible section so you know how much liquid is inside. I’ve used black duct tape, paint, or gluing on aluminum foil.
  • Cut a hole for your net cup in the lid and test that it fits correctly.
  • Again, black out the remainder of the lid so not too much light can get in the reservoir.
  • Put it all together and add enough water to go about 1/8″ above the bottom of the net cup. Mark that level on the side of the container.
  • If you have seedling, rinse the roots of dirt and add it to the net cup. Fill it with support material like expanded clay balls or perlite. If you have seeds, expand your peat puck by putting it in the now-wet net cup. Once it’s expanded, add 2 seeds about 1/4″ down in the peat. Keep it watered to the mark on your container until the plant has 4 leaves. At this point, cull the weaker seedling, if there is one.
  • Get the plant settled by fertilizing with a quarter strength fertilizer and a rooting solution (GH RapidStart or Super Thrive). Rooting hormone is not completely necessary, but does speed up the grow.
  • After the roots are long enough to reach down into the reservoir a few inches, change out the nutrient solution with one that is at full strength. Fill this to a level that leaves about 2 inches of breathing room for the tops of the roots. mark that level on the container.
  • Get a 1qt bottle and fill it with half-strength nutrient solution. This is your refill solution and tells you when it’s time to change out the nutrients. Keep refilling the reservoir to that mark you made 2″ below the net cup with this solution. Once the refill bottle is empty, Make your next refill a complete cleaning of the reservoir and a full refill of full strength nutrient solution.
Indoor tomatoes setup in 2.5 quart paint bucket.
My setup for indoor tomatoes. Aluminum foil blocks light and also the government mind control rays.

From this point on, grow your tomatoes steadily by continually refilling the container to the mark and cleaning out after you’ve refilled a quart’s worth.

Tips for better tomatoes

  • Ventilation helps the plant grow. Putting the plant in a place with air flow or using a small fan will be sufficient.
  • Keep your tomato clusters to about 4 tomatoes. Any more and they will mature at vastly different rates and lead to small fruits.
  • Yellowing lower leaves tell you that the plant needs more nitrogen. This is a good time to add a touch of the household plant fertilizer to rejuvenate it.
  • Pluck the “suckers”, or fruitless secondary branches. The main stem will have branches where leaves come out, and those will have branches that either bear fruits, or just spread out. We don’t want the spread, so cut those off. WikiHow has a good article on tomato pruning that illustrates the basic pretty well.
  • Prune the lower branches to only fruit-bearing ones. There isn’t enough light down there to justify the plant growing out leaves.
  • Harvest as close to when you want to consume as possible. Tomatoes lose flavor fast.
  • Let the ripe tomatoes sit on the plant for a week after it turns fully red. This develops flavor.

That’s it. Sure, it’s some work, but you will be rewarded with a steady supply of tomatoes as long as you keep the plant up.

2 years ago