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How to Grow Tomatoes Indoor with Lights?

When it comes to growing tomatoes indoor with lights, two questions pop up in everyone’s minds. There is a ‘why’ and there is ‘how’. Let’s answer the why part first.


Growing tomatoes indoor comes with various advantages. First, this technique allows you to enjoy fresh, juicy and home-made tomatoes all year long without having to worry about the outside temperature, even when cold weather has rendered your outside garden useless.

Second, since tomatoes during their growth period requires direct exposure to sunlight for six to more hours every day, growing them indoors, under suitable lights, prevents you from having to worry about cloudy outdoors.

Thirdly, you will enjoy the same set of delicious, pulpy and vibrant tomatoes from your indoor setting that you’re used to buying from your local shop. And on top of everything else, you’ll end up saving money that you’d otherwise have forked out on tomatoes.

How to Grow Tomatoes Indoor With Lights?

Plants on a tray indoors

Now you’re fully satisfied with the why part, let us turn our sights to the how part. As in how to grow tomatoes indoor with lights. And this is where we come in. In this article, we’ve prepared a comprehensive guide for all those tomato aficionados who want to enjoy homegrown tomatoes all year long.

In the paragraphs that follow, we’ll provide you with key insights using which you’d be able to grow tomatoes indoors with lights. We’ll also point out mistakes that you must avoid committing to make the most of our technique.

Here’s a step-by-step guide to grow tomatoes indoors with lights:

1) Choose the right tomato seed

chopped tomatoes on a cutting board

There are two types of tomato seeds available in the market: Determinate and Indeterminate. Choosing any one of these two seeds can go a long way in your pursuit of getting optimal yield. This decision will also affect the size of your tomato plant which can be vital if you have a limited indoor space.

Here’s how you can choose between determinate and indeterminate tomato seeds:

Determinate Tomato Seeds

Determinates are the ones which, once they reach a certain specific height, stop growing any further. They ripen early as compared to their indeterminate counterparts and produce all their yield at once. It means that if you’re limited on space, it might be a good idea to go with determinate seeds.

However, if you’re interested in a regular supply of fresh tomatoes, you should keep in mind that determinate tomato seeds produce very little, if any, new batches of fruit after the first batch. They will stop growing after producing their first yield, which is why they are also referred as ‘bush’

Indeterminate Tomato Seeds

Indeterminate tomato seeds keep on growing, and producing, throughout the growing season. These tomato seeds ripen all the time which might make it a suitable purchase for all those tomato growers who want to enjoy a steady supply of fresh tomatoes.

Having said that, they often grow into large bushes, so you must prune them on a frequent basis. The indeterminate tomato seeds will also need to be caged or staked to assist their large structures or otherwise, they tend to sprawl on the ground.


2) Choosing the Right Location

a tomato plant outdoors

Location plays a huge role in the growth of tomatoes. A tomato plants germinates best under warm and humid conditions, and it requires plenty of light. You should choose a soil that is highly porous, slightly acidic and offers good drainage. 

Another thing which one needs to keep in mind while growing tomato indoors is the right headspace. Your tomato plants will grow in length, especially if it is of the indeterminate type, and than there are the lights which one needs to hang on top of them.

Therefore, it is beneficial to choose a suitable growing location for tomatoes with a decent headspace above your crop. Both these factors ensure that your tomato plant avoids stunted growth and comes up with the best possible outcome.

3) Choosing the Right LED lights

Boxes of grow light bulbs

LED lights are beneficial for homegrown tomatoes in more ways than one. They don’t much produce much heat which saves the plant from heat damage. They are also height adjustable so your fruit, plant or leaves won’t get damaged by coming in direct contact with the panel.

Similarly, a full spectrum LED light, whose intensity can be lowered or increased, provides just the right amount of light depending on the stage of your plant growth. This is important because when a tomato plant is highly sensitive, you just can’t harvest and forget with this fruit crop.

Another factor which comes handy with LED lights is the fact that they can be used all year long. You don’t have to wait for a proper amount of sunlight for the growth of tomato plants with these lights and as a result, they tend to increase the overall tomato yield.

Here are some factors which one needs to keep in mind while selecting the right type of LED lights.

a) Temperature

A typical tomato plant requires exposure to light for 8 or more hours every day. This is very important for efficient fruit production. Otherwise, colder temperatures will lead to stunted plant growth and consequently, a lower yield of tomato fruits.

During the germination phase, it is recommended to keep the temperature between 71 to 75 degrees Fahrenheit. As the plant evolves, the temperature range needs to be increased between 75 to 79 degrees Fahrenheit in its growth stage.

Therefore, you might want to choose a LED light that comes with temperature control for the proper growth of your tomato plants. Otherwise, you may have to buy different LEDs as your tomato plant goes from one growth stage to the other.

b) Length of Illumination

High quality LED lights allow you to control the time duration during which the tomato plant is exposed to illumination. This feature is highly beneficial because otherwise, if the temperature drops below a certain limit, colder temperatures can lead to a stunted plant growth and a lower tomato yield.

For the germination period, a tomato plant needs to be provided with adequate amount of light for 12 hours every day. This should continue for the first 3 to 5 weeks of plant growth. The plant will adsorb carbon dioxide in the remaining period which comes handy during the photosynthesis process.

After the germination period, increase the illumination period for 14 to 16 hours every day. Keep this routine for the next 2 to 3 weeks before lowering the illumination time for 10 hours daily until the ripening period, or when you’re ready to transplant the seeds.

4) Sowing the Seeds

a woman sowing seeds

Once you’ve set up the right set of LED lights, it’s time to sow the tomato seeds. Start with choosing an appropriate set of starter trays filled with a suitable mixture of soil. Plant your seeds at 6 cm from each other and insert them 3 to 4 mm deep in the soil.

This will provide your tomato seeds ample room for growth. Another thing which one needs to keep in mind that regardless of the drainage capacity of your soil, you should never overwater your seeds. You can also cover the seedlings with a foil just to make sure that the moisture and heat is kept inside.

5) Transplanting the Seeds

close up of a growing plant

Once the germination period is over, which usually takes 5 to 10 days in an indoor setting, it’s time to move your seedlings to another pot. Your leaves will be around 3 inches tall at this point with a couple of leaves.

For transplanting, choose a soil as mentioned above and your pot should be big enough to accommodate the growth of your seedlings. A typical pot, ranging from 3.5 to 5 gallons, will do the trick for this purpose.

Add a little bit more soil around the seedlings. This will assist in the development of a strong room system. Use fertilizers after every two weeks during this period and add a light amount of water.

You should also turn the location of your tomato pots just to make sure that the right amount of light is available to all sides of your tomato plant.

6) Staking the Seeds

tomatoes on table next to a pot plant

If you’ve grown tomatoes in the past, you might know that tomatoes cannot hold straight on their own. One needs to stake them for support or otherwise, they will stretch on the ground.

Use wooden posts for staking the tomato plants. Make sure no amount of chemical is used in the production of these posts because chemicals will alter the soil composition. Insert these posts 3 to 6 inches deep in the pots but make sure to do that after the flowering or planting period. Otherwise, you might end up causing damage to the root system.

7) Pollinating the tomatoes

fingers near a pollinating plant

The process of pollination is taken care of by bugs in an outdoor setting. However, since we are growing our tomatoes indoors, we have to take care of it on our own. This will keep our plants healthy and ensure an optimal fruit production.

Start with by holding your plant at the top and shaking it in a gentle manner. You can also shake the plant step during the blossoming period as both these techniques will ensure that pollen is distributed evenly throughout your plant.


8) Pruning the Plants

hand pruning a plant

Pruning ensures a healthy plant growth while discouraging diseases. This step is important especially if you’ve chosen to grow indeterminate seeds that will grow to unpleasant lengths if allowed to grow on their own.

You will realise that your plant is ready for pruning as soon as the leaves under the first flower start turning yellow. Remove those leaves, and other suckers, by turning them back and forth. Suckers, as evident from their name, don’t add much to the overall plant grown and they don’t tend to grow much as level.


Frequently Asked Questions

What is the best grow light for tomatoes?

The Original LED Grow Light Bulb is the best for growing tomatoes. Apart from offering full-light spectrum, it has low energy consumption and emits very little heat. This grow light bulb also comes with a 3-year warranty and is incredibly easy to install, too.