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How To Grow Hydroponic Tomatoes Indoors With Lights (Step By Step)

When a heavy breeze comes through our kitchen windows and ruffles our indoor garden, the room is always instantly filled with the earthy, spicy aroma of tomato.

Yes, you read that right. I’ve successfully been growing hydroponic tomatoes indoors with lights, without a balcony or proper garden bed. It’s surprisingly easy with the right tools. Heck, one of our tomato plants is so tall it’s almost reaching our ceiling (I probably should prune it, but it looks so happy, I just can’t!)

In this post, I’m sharing how to build a tomato hydroponic system in your apartment or home so you can get starting growing tomatoes year-round, even if you don’t have outdoor space. If you are looking to build a larger hydroponic tomato farm, this post will still be relevant as I drop tons of tips on the basics of how to build and use water hydroponic systems! 

We grow tomatoes inside on a small scale. You can apply this tutorial to any scale of tomato garden!

Why We Choose Growing Tomatoes Hydroponically Inside With Lights

My wife Kara and I live in a small apartment in San Francisco without any outdoor space at all. We practice urban homesteading and a big part of our lifestyle is growing herbs and veggies inside our apartment.

I started us off with traditional gardening with soil but found using hydroponics is much easier and more successful for most plants, and especially when you are using grow lights inside a house or greenhouse.

Kara was awesome and built our grow system with lights all by hand after a few runs to Home Depot. We have two levels, the bottom with grow lights and the top we use an AeroGarden Bounty Basic system and that’s what we grow our tomatoes in (more on that below.) You don’t have to use this grow system, though. 

What Is A Hydroponic Grow System?

In short, a hydroponic grow system is garden that doesn’t use soil for plants. It’s all water! This is also known as a deep water culture system, or DW for short. 

Plants need a flow system of water. When you pot them in soil, this flow system happens when you water the plants and the water seeps through the roots and out of the pot.

When it comes to growing plants in water, they can’t just sit in still water otherwise they’ll be prone to root and won’t grow easily, or at all. You need a system that uses a nutrient film technique with a water pump, and that’s where a Hydroponic Grow System comes into play.

Since hydroponic tomato farming doesn’t require waiting for the summer season to grow, it can be done year-round.

Best Hydroponic System For Tomatoes

The best Hydroponic system for tomatoes will totally depend on you, your space and your growth goals. We have a smaller space, so we use small yet a complete grow system since it’s easier. If you have a large greenhouse, you may have room for a nutrient film technique system using pipes so you can grow many, many plants at once. 

  • AeroGrow Basic: This hydroponic tomato system has 9 holes and we can fit up to 2 tomato plants and some herbs in it at once. We love it for small spaces like ours! 
  • Gardyn Home Kit 1.0: If you have a slightly larger home space, opt for this kit instead. You can place it on the floor to allow your tomatoes to reach super tall. There’s also space for other plants here, too! 
  • eSuperegrow: This kit comes with a 60 inche trellis to support your tomato plants! 

right now we are growing a tomato, cucumber and basil in our AeroGrow

How To Grow Tomatoes Hydroponically Step By Step

1. Pick Or Build Your System

First get your system set up and running. If you are using an AeroGrow or something similar, all you need to do in pick a shelf. These systems come with starter grow kits so you don’t need to shop for anything else. 

If you are building your hydroponic tomato system, your supply list will vary based on if you are doing an indoor tray grow system, or doing the nutrient film technique with pipes. No matter what you’ll need:

2. Use A Nutrient Solution In Water

Because the plant growing medium is water, you need to make sure that water is fresh/clean and has the nutrients plants need to grow. This is way less of a hassel than garden tomatoes, which need to be watered everyday in the hot summer, but you still need to care for them twice a month.

  • Once A Month: swap out the water with totally fresh water. If you see any mold growing, clean it asap and rinse well so soap doesn’t linger in the water basin. 
  • Every 2 weeks add 3 droppers of your nutrients to the water. This is how much we add to our AeroGrow which holds 9 plants. If your system has more, adjust accordingly to make sure you are feeding enough.

It really doesn’t matter what nutrient solution you use. We currently use Modern Sprout plant food, but cheaper brands like MiracleGrow are fine. 

3. Best Tomato Seeds To Use

We think growing Cherry Tomatoes are the easiest to do with indoor hydroponics as they are small and tend to grow many fruits in each harvest. This basically optimizes limited indoor space. We haven’t yet tried Roma Tomatoes but since they are a similar size, they are also probably easy to grow inside with lights as well.

Large tomatoes like Beefsteak, Black Krim, Better Boys, etc will be harder to grow if you are tight on space like we are in our apartment. I would only suggest you tackle this if you are using a nutrient film technique with pipes and a large indoor greenhouse so there’s space for these plants. 

4. How To Plant Your Seeds

Planting tomato seeds hydroponically is super easy and clean. Most kits use a variation of what we call The Cone, but you may have to buy yours separately. A sponge sits at the top of the cone and the cone is rested in a hole at the top of the water basin. The tip of the cone reaches down to the water and the sponge sucks it up. 

No dirt is needed! First, fill your water basin with water and add the nutrient drops, 2-3 droppers full per 9 plants. Then, place your cones and sponges into the holes. Now it’s time to add the seeds.

A good rule of thumb is to always plant 2 seeds per hole in case one doesn’t germinate. Tuck 2 seeds into each sponge/cone and then cover with the clear plastic dome. Once sprouted you can remove the dome. 

5. Light Timers?

Before you walk away, make sure your light timers are working and set up. You need to use red, white and blue lights for tomatoes. 

  • White light mimics sunlight and all plants need it to grow.
  • Red light is for sugar production and flowering.
  • Blue light is good for chlorophyll production. 

All grow lights I’ve seen have an option to turn all 3 light colors on at once. Use this setting. While the seeds are sprouting and growing, keep the lights on for 16 hours each day. Once the plant has reached a good height and maturity, you can be reduced to 14-15 hours on each day. 

6. Pruning & Supporting

Keep in mind that tomato plants grow tall and need a trellis or support system in order to stand up and grow in the right direction (up, not out!) We just string and tie it to our AeroGrow arm, since it stretches 2 feet tall. Depending on your system, you may have to build a trellis for your plants

On top of support, you need to prune your plants to keep them healthy and growing the way you want. I prune off dead leaves and sometimes even cut off new shoots when I want energy to be focused on other branches that have already flowered. 

7. Harvest When Ripe

Last step is harvesting! Reward yourself for all your hard work looking after your plant babies. Pick, eat, enjoy and wait for the next round of fruit to come. 

How Fast Do Hydroponic Tomatoes Grow?

I found Hydroponically grown tomatoes to have a similar life span as plants my family would grow in our traditional outdoor gardening growing up. It takes a while for the tomato seeds to start producing a stalk. Our plants took about 2 months to produce flowers and then another few weeks for the fruit to grow and ripen.

But, since that first harvest, our plant has be regularly producing flowers that turn into fruit. We’ve had 3 harvests since October (I’m writing this in January) I estimate we can get this guy to give us fruit at least 5-8 times per year, if not more.

Hydroponic Tomatoes Problems To Look Out For

Tomatoes need a LOT of water to grow. Our major problems is keeping the water reservoir filled and clean with fresh water while we are traveling. We also run, a lifestyle travel blog and thus sometimes have to be gone traveling for 1-2 weeks at a time, sometimes more. 

When this happens, we get our cat sitter to replace the water in our AeroGrow system and thanks to the automatic timers built-in, the tomatoes and other herbs we plant in the system always survive as long as someone is giving them fresh water. (But that’s not the case for our pot-herbs under grow lights. They need more water and we’ve started harvesting those down right before large trips.)

The second issue we face is with the roots of the plants. Large tomato plants also have HUGE root systems and you may simply run out of space in your basin. That’s what happened to us.

We ran had 2 tomato plants growing but the root systems filled the basin so much, we had to move one tomato plant to a new system, but eventually let it die as we just don’t have the space in our apartment for two massive plants. If we had a greenhouse or a plant room, this wouldn’t have been a problem. Just something to keep in mind! 

Otherwise, these are pretty easy to maintain and grow. 

I hope this helps you build your own indoor tomato growing system! I’ve found so much success in hydro tomatoes that even in the future when we have an outdoor garden, I still plan on doing greenhouse tomatoes in hydroponics so we can have a fresh harvest year-round (on top of outdoor plants in a summer garden.)

But for now, our trusty little apartment tomatoes are going strong. 

If you have tips to add please drop a comment below so everyone can see! Got questions? Comment or DM on Instagram @soulhomesteading and I’ll try and help you out. 

Happy growing! 

T.J. O’Brien

Tuesday 9th of April 2024

How can I top an indeterminate cherry tomato plant to keep it short enough to stay under the grow lights? I have an Ahope hydroponic garden.

Matt Rippin

Monday 25th of December 2023

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