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light requirements for tomato plants

Posted by jordanvv z8 WA (My Page) on
Wed, May 11, 05 at 1:00

Hi gardeners,

We live on the 3rd floor of an apartment building and decided to make a little (indoor) window garden - partly as a "science" lesson for our two year old. The building gets good light from the east and the five tubs now have a total of 10 tomato plants about eight inches high.

I'm wondering however if the east facing exposure will be enough light (about 5 or 6 hours/day on days that the sun shines) for the tomato plants to actually produce fruit.

I would consider grow lights, but that would add considerable expense. Maybe the plants will just take longer grow and produce fruit?

Any thoughts?

Thank you for your help,

Follow-Up Postings:

RE: light requirements for tomato plants

Is this on a balcony?

Because the light you get through an average window isn't enough.

But a balcony is a possibility.

Anything less than 8 hours will result in stunting. As an example, I built a greenhouse last year.

The front of the greenhouse faces South. Plants near the South entrance grew slowly because of the shade from the doorframe, etc.

Plants outside, caught in the shade thrown by the greenhouse after six PM, were also stunted compared to identical species just a few feet away.

You could maybe help by setting up reflectors. Cardboard, aluminum foil, behind the plants to boost the light levels.

I don't know for sure that more brightness will compensate for less duration, but give it a shot.

As for artificial light, if you use fluorescents, you'll need to mount the lights behind the plants so you don't shade them.

And boosting the light by overdriving the fluorescents would help a lot.

But the tubes would have to be within a few inches of the foliage.

I've been thinking of makine a "light wall" in my basement to overwinter a few tomato plants, just to stave off Tomato Withdrawl Syndrome.

Overdriven Fluorescents, mounted on the concrete block wall in the back corner, some plants in 7 gallon buckets.

Might work.

RE: light requirements for tomato plants

You'll get tall, spindly plants and possibly a few fruit.

A more fun outcome would involve a genetically small variety (i.e. one of the dwarf cherry tomatoes) and a shop-light fixture to provide supplemental light.

RE: light requirements for tomato plants


I agree with the others. If you've chosen ordinary garden-variety plants, it is unlikely that you will be able to provide the necessary growing condintions in your appartment to produce tomatoes. (IMHO) If you don't mind starting over, get some seeds for dwarf plants, like Red Robin, Tiny Tim, or Micro Tom. You can find sources for these via an Internet search. These varieties can tolerate low-light, but a fluorescent fixture would help. They only grow about a foot tall, and will produce bunches of 1" or so tomatoes.

Good Luck!

RE: light requirements for tomato plants

Howdy jordanvv,

It seems that you have less of a "Science Lesson" and more of a "Science Experiment".

There are five steps for using the Scientific Method:
1) Observation and Description
2) Formulating a Hypothesis
3) Derive a Procedure to Predict Results
4) Test
5) Repeat Steps 1 through 4 until done

The fact is that no one can really answer your questions except you and some time for observation and testing.

I like that there are two plants in the same pot. Both Eric and John Dal have very good suggestions about trying different species of tomatoes. If you try two different species in the same pot, then some of the variables will be controlled and you can see how different species fare under very similar growing conditions.

Since you also have five pots, if they are staggered in distance from the windows, then you will be able to see at what point the light fade becomes difficult to produce fruit.

It makes sense to keep a written record of your observations because it will take time and generally speaking, plants can grow reasonably well under some pretty adverse conditions. Measuring is a good way to keep track of these things.

Artificial light fades fast. You will need quite a bit of it for ten plants. You may consider getting a 250 Watt growlight and shining it on one tub only. This will give you a good comparison with the plants which do not get supplemental lighting.

Lastly, while your two year old may enjoy eating sweet tomatoes, as far as the "Science" part goes, can your child even say, 'hypothesis?" Hmmmm. Maybe dad is indulging his gardening by using his kid. Well, no criticism in this forum--I'm sure it will be copied.

RE: light requirements for tomato plants

Your just going to need more light. Cut the amount of plants and get a decent grow light. You don't need to run any experiments, Tomatoes need a lot of light to produce fruit, 6-8 hours daily of direct sun, more is btter...

Good Luck...

RE: light requirements for tomato plants

im growing eggplant,tomatoes,peppers,cucumbers,squash,strawberries,melons under lights just fine right now. i use a 400 watt metal halide for an 8 squarefoot area. i have 4 of them.

RE: light requirements for tomato plants


I'm trying to grow tomatoes inside too. I don't have a grow light yet. I looked online and they appear expensive. But one site mentioned a lamp, which was a lot cheaper. What is the difference between a grow light and a grow lamp. Any recommendations for a place to get a cheap, but good light source?


RE: light requirements for tomato plants

The vapor-tights are a 150 watt HPS lamp, thats ballast, socket and bulb for 20 bucks. Yep. Cheaper than your average 2 socket 48 inch florescent shop light and a couple of floro tubes to put in it. And let me tell you, a hell of a lot more effective. If you go this rout you'll probably also want to snag one of their 15 inch reflectors to go along with it. Just click on the 'accessories' link underneath the picture. Snag one of those and remove the aluminum and glass shield from around the bulb and you have yourself a killer sub-40$ grow lamp. Good luck and happy growing!

Here is a link that might be useful: Cheap HPS

RE: light requirements for tomato plants

Can I change the HPS bulb (it's a 150 watt, ED17, medium base) with a 150 watt MH that is also 150 watt, ED17 and a medium base?


RE: light requirements for tomato plants

Wordwiz, did you get an answer to your question?
"Can I change the HPS bulb (it's a 150 watt, ED17, medium base) with a 150 watt MH that is also 150 watt, ED17 and a medium base?"

I would sure like the answer too.

RE: light requirements for tomato plants

Not yet! I may end with leggy plants, though there are a lot worse things in life. I bury them to their bottom leaves so I'll have to dig a deeper hole.


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