Tomatoes are one of the plants that represent summer. The aroma, the bright colours, and the yummy taste all remind us of a sunny summer day. Gardeners often can’t wait to start growing them. Today we want to talk about how to grow tomatoes indoors. Can you, should you, and how to do it.
Can you grow tomatoes indoors?
Tomatoes are a great plant to grow indoors. You will not need any special varieties for indoor growing. All tomatoes can be grown indoors. Since tomatoes are perennials, you can actually grow a tomato tree indoors.
Tomatoes also grow well from cuttings. If you don’t have room for a tree, but want to grow the same great variety continually, just take a cutting to start a new plant whenever the old one outgrows your room.
Tomatoes are pollinated by wind, just checking the plant every few days is enough to achieve the same effect.
We have grown tomatoes indoors for a few years now, and we can assure you it really does work well.
Why grow tomatoes indoors?
Living in a cold, northern climate means we have to endure long, cold winters. With frost possibility in late May, it seems like our winter does last 9 months. We can’t wait for spring. We want to start planting. We want to grow a garden. It might just be one plant, or a whole indoor garden, but it is so fun to have a bit of summer indoors.
Another reason to grow an indoor garden is extreme weather conditions outdoors. For us it is the cool and short summer, for you it might be extreme heat… too much rain… hail… you get the idea. In order to grow tomatoes earlier and enjoy them longer, we grow some of them indoors.
You can grow tomatoes indoors for part of their life, and move the plants out as soon as the weather improves. Note, I’m not talking about seedlings, rather about mature plants grown in a container. This will really give you an early start if desired. Make sure to harden off the plant first by either moving it out for a few hours at a time, or covering it with a Plant Protection Blanket.
You can also bring in a plant in the fall and prolong its life span as much as you desire indoors, just make sure not to take in many bugs as well. Note again that the plant has to be in a container. You can’t transplant a mature plant from outdoors to indoors, it would die.
We grow tomatoes indoors all summer long at big south facing windows. We often call our window room a greenhouse, but technically it is not. Those are just windows we grow plants at. A sun room or a bay window would also work very well.
How to grow tomatoes indoors
Tomatoes are a summer crop and need lots of sunlight in order to grow and produce fruit. If they do not have enough sun hours, the plants will not die but will not produce fruit either. For this reason we do not grow tomatoes during the winter months.
From October 28 till February 14 our daylight is less then 10 hours. Calculate your garden’s “below 10 hour days”. Also often the much needed winter sun is behind neighbouring buildings and trees. Growing year round we can really see how much impact the “below 10 hour days” have.
The best time to start growing indoor tomatoes is right at the edge of the 10 hour day. We would recommend to use grow lights for the seedlings, to give them a healthy start. Read more on how to start tomatoes from seeds.
Just like for the outdoor garden, the seedling will be ready to be planted just before putting forth buds.
Plants are best grown in good organic soil out in the garden. We can’t provide that in our indoor garden, but we can do the best we can.
Personally, from our experience, growing indoors is easiest in hydroponic. It is a clean solution that provides the plants with all needed nutrients. Read more about growing the Kratky hydroponic way, and growing a Tower Garden.
We have also had good experiences growing in soil, however to be honest with you there are more challenges. You will need a good soil mix that provides the plant with all nutrient. We use Mel’s Mix from the Square Foot Garden:
1/3 peat moss
You can find all of these ingredients in a garden center or Home Depot. You will find all the needed info in Mel’s informative book.
Since tomatoes are heavy feeders, you will need to fertilise them. Worm casting is the best, and more and more stores carry it nowadays. Another great natural fertiliser is Bone Meal.
Watering is also very important indoors. At a sunny window plants dry out very quick. Plus, containers do dry out quicker anyways. You will have to make sure to be able to water regularly, in the heat of summer every day.
Tomatoes like it warm. A cooled down indoor room is not the right place for them. Even though the sunny window might have a different temperature than the room itself, make sure to measure the temperature. For growing tomatoes you want to have around 17C (62F) at night and 26C (79F) during the day.
We grow out tomatoes in the grow room at the back of our garage. It gets really warm in there, up to 30C (86F) and the plants love it. We have tried to grow tomatoes in the same room during the winter and found it was not worth it since the temperature there does go below 12C (53F).
However, you can grow tomatoes indoors all winter long, you just have to make sure there is enough light and heat for them.
Grow tomatoes indoors in succession
This end of August taken picture is a great example of succession indoor tomato planting. The first 3 plants are plants that have been started in late winter and grew here all summer, producing lots of fruit. One has a sucker that will be there after the plant is done with the old fruit. I will just cut back the plant and leave the sucker. Note: I do prune suckers, this is an exception because I can have a new plant from the old root. See more about pruning tomatoes here.
The next 3 plants in the picture are young plants that have been started from cuttings in the summer. They have fresh fruit growing. After that there is empty space because some of the spring tomatoes were done and I will use the space for new plants. I will not start new tomato plants at this point (late summer), but I’ll start greens for winter growing.
I have tried starting new plants in the fall to grow tomatoes year round, but the results in our cold climate (Zone 3 in Canada) were not worth it. We grow tomatoes indoors in spring, summer, and fall. In the winter we grow greens.
There you have it, a guide on how to grow tomatoes indoors. It is easy if you can provide good lighting, soil (or hydroponics), and temperatures that tomato plants love. Try it and let us know how it goes. For us it really is worth it. We harvest lots of yummy tomatoes from our indoor garden every year .