Can I Grow Tomatoes Indoors on the Tower Garden?

When I first started growing on a Tower Garden, I tried growing inside tomatoes that came with the Tower Garden. They were leggy (cue the “Attack of the Killer Tomatoes” music here) and attracted insects. I switched to lettuce and did much better, but never investigated why the tomatoes didn’t do well. When I wanted to try tomatoes indoors again, I asked questions and did some investigation. I discovered that it’s possible to grow tomatoes indoors, but they won’t do near as well as growing outdoors. There are 2 reasons why.

  1. Pollination
  2. Light spectrum

We have to mimic inside what God designed perfectly to grow flowering fruits and vegetables outside.


Bees pollinate your blossoms which produces the fruit and vegetables. Indoors you’ll need to pollinate the blossoms yourself. That trick can be learned – and with the declining bee population, it isn’t a bad skill for outdoor gardeners to know.  How you pollinate will depend on what you want to grow.  Peppers, for example, pollinate within the same flower.  So all you have to do is shake the stalk. Tomatoes pollinate between blossoms so you’ll need a paint brush, etc.  I can’t go into all the differences here and how to pollinate.  That’s what Google is for.  🙂


But the most difficult problem is the light spectrum. For a plant to flower and produce fruit, it needs light in the low end of the spectrum—around 2,700 Kelvin. For a plant to produce nice leaves it needs a light in the high end of the spectrum—around 6,500 Kelvin. So tomatoes, for example, need a 6,500 Kelvin light during the leafy part of growth. Then they need a 2,700 Kelvin spectrum to produce the blossoms and fruit.

Outside, the tomato gets this as the summer progresses. During the heat of the summer, the light is on the higher end of the spectrum helping the plant to produce nice leaves. As the summer progresses and the tomato grows, the light switches to the lower end of the spectrum helping the tomato to produce the blossoms and fruit. (Here’s more than you probably ever want to know about light spectrum.)

The lights that come with the Tower Garden are in the 6,500 Kelvin range. This spectrum of light produces great leafy greens, but won’t help produce the fruit.

Could you switch bulbs mid-way through the growing cycle of a tomato plant? It’s possible, which would make it a great experiment for an upper-level science class.

What about Full Spectrum Bulbs?

Full spectrum lighting does not contain both ends of the color spectrum. Full spectrum lighting is usually the higher end of the spectrum. I’ve seen bulbs marked ‘full spectrum’ that are 6500 Kelvin and some that are 5,000 Kelvin.  Manufacturers don’t even agree what Kelvin full spectrum lighting should be.  The best thing to do is look at the Kelvin rating of the bulb and purchase accordingly.

But They Grew Tomatoes!

You’ll hear that someone has had ‘success’ growing fruit, inside, with the lights that come with the Tower Garden.  They might be growing near a window letting natural light in or some other reason that you can’t duplicate. It’s also possible that their definition of ‘success’ isn’t your definition. They might be very happy getting 5 small strawberries from one plant. Maybe you’ve grown strawberries outdoors and gotten 25 large strawberries from one plant and want that same production indoors.

In order to get the same production inside as outside, you’ll need to create the same environment inside as outside.  The two main factors are light and pollination.  Temperature is also a factor, but that’s a good topic for another article.

So What Do I Do?

Have fun trying to grow indoors or out whatever you want. I have brussels sprouts and egg plant growing in my Tower Garden now.  I don’t know if either will work, but it’ll be fun to try.

Seed Starting Procedure

The Tower Garden comes with directions for starting seeds in daylight. Joe of Level2 Concepts introduced me to a procedure that starts seeds in the dark. I’ve adapted his procedure a bit and have it outlined here.

Most plants like a pH of somewhere between 5.5 and 6.5. Rockwool has a natural pH of around 8.0. To give your seeds the best chance of starting, you’ll need to soak the rockwool in water that’s between 5.5 and 6.0.

  1. Soak rockwool for 30 minutes or more in water with a pH of between 5.5 and 6.0.
  2. Cut the bottom off a 5 gallon ice-cream container or use the bottom of the growing tray that comes in your Tower Garden with the lid removed. (I’ve also used butter containers, etc.) Put masking tape around the outside of the bottom of the ice-cream container and write numbers on the masking tape to coincide with the rockwool cubes. The ice-cream container bottom works well because you can get 10 rockwool cubes around and 4 in the middle. On a piece of paper write down the numbers and the seeds you planted.
  3. Shake excess water from each cube, but do not squeeze the cube. You can also use a salad spinner to shake off the excess water.
  4. Place rockwool cubes into the bottom of the growing tray or other plastic container.
  5. Sprinkle seeds into the hole in the middle of the rockwool. There’s no set rule for how many seeds per rockwool. For arugula, I sprinkle 15 or 20 and don’t thin them. For bibb lettuce, I’ll plant 6 or 8 and only let 1 seedling grow. Generally the smaller the seed the more seeds you should plant. You can always thin the plants with scissors later.
  6. Pour about 1/4 inch of pH adjusted water in the container.

    10 rockwool cubes in the ice-cream bucket bottom

    10 rockwool cubes in the ice-cream bucket bottom

  7. Put black duct tape around the top of the ice-cream bucket and place over the rockwool so the seeds are in the dark. (I’ve also used a box for this.) If your house is cold, you’ll get quicker results if you use a plant starter heat mat. I got mine at Menards, but here’s one on so you get the idea.

    The top of the ice-cream bucket covered with duct tape.

    The top of the ice-cream bucket covered with duct tape.

  8. Every day, replace the water with fresh pH adjusted water.
  9. Check your seeds every 12 hours or so to see if any have sprouted. Most lettuce and herb seeds will germinate in 36-48 hours. Uncover the seedlings and place them in another container on the base of the Tower Garden with the lights turned on. When you see white fuzz near the seeds, you want to uncover them. This is important. If you wait too long, your seedlings will become leggy. Your goal is to have short plants with large leaves.
    Arugula seeds that are ready to go under lights. I break a rule here and plant the arugula on top as well as inside the hole.

    Arugula seeds that are ready to go under lights. I break a rule here and plant the arugula on top as well as inside the hole.

    Good start for seedlings

    Good start for seedlings

    I have a 12″ fixture with a 6500k T-5 bulb that I use for seedlings. This allows me to get the light right close the plants. The closer the seedlings are to the light, the better they’ll grow. I’ve also used a regular desk lamp with a 6500k bulb to get the light as close to the plants as possible.

    Regular desk lamp with a 6500k bulb.

    Regular desk lamp with a 6500k bulb.

  10. Once a seedling is under the light, you need to drain and replace the water every day. To do this, mix up a container (I use an apple juice container) of half pH adjusted water and half water from your Tower Garden. This will give your seedlings a little nutrient solution.
    • Day 1: Replace water with half nutrient strength
    • Day 2: Replace water with only pH adjusted water
    • Day 3: Repeat Day 1
    • Day 4: Repeat Day 2
    • etc.
  11. Continue with the above until you see roots starting to exit the rockwool. Once you see roots on the bottom, it’s time to put the seedlings into the Tower Garden.

I’ve used this procedure successfully for tomatoes, peppers, various lettuces and herbs. Your mileage may vary depending on the crop and your environment.

Adapted from a seed starting procedure by Joe of Level2 Concepts.

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