I've started growing a tomato plant a month ago and it is still pretty small. Around 7 cm high.

I grow it with a small fluorescent light ( T8 model ) in my basement.

Why is it growing so slow?

  • Is it the inadequate temperature?
  • Too much / not enough light
  • Inadequate water amount
  • Too small/big pot size
  • 2
    More info required. You haven't said what temperature you're keeping it at, whether you grew it from seed, what size pot its currently in, what type of growing medium you've used.
    – Bamboo
    Commented Nov 26, 2012 at 15:23
  • 2
    Also whether you're using HO T8 lights, how many, and how close they are to the plant, whether you're turning them off for 8 hours a day.
    – Bamboo
    Commented Nov 26, 2012 at 15:28
  • temperature is around 20 C. from seeds pot size is app 7 cm in diameter and 15 cm high. Regular T8 from homedepot, 2 tubes they are 50 cm above the plant I used to turn them off 6hrs a day, but know they are always on because I thought they would grow faster
    – Conrad C
    Commented Nov 26, 2012 at 16:00

1 Answer 1


Regular T8 is probably not giving enough light, the High Output version is usually used for tomatoes, and that version is referred to as HO T8 Growlight fluorescent tube rather than just T8 tube. If ordinary fluorescents are used, these are more usually T12, and are much better at growing leafy crops such as lettuce than fruiting ones like tomatoes.

Tomatoes need a minimum of 8 hours darkness per day, between 8-10 hours is optimum, so the lack of that, coupled with the use of standard T8 lights, might be the reason. Note also that plants grown where air is wafting around them (not blasting) grow stronger, with thicker stems, than plants in an area where air movement is virtually nil most of the time, due to a process named thigmomorphogenesis (just in case you want to look it up).

The optimum distance between the plant and the light should be between 11 - 51 cm, but better results are achieved with the lower measurement (4 inches, or 11 cm), so moving the light closer would be a good idea.

On the pot size, once it starts growing properly, it should be in a pot that's an 8/9 inch tomato pot, so around 23cm, for good cropping, with the usual high potash feeding regime.

  • What do you think is more responsible for this slow growth? The lack of darkness or of light? Can I counter this lack by adding custom LEDs? If so, what wevelenghts would I need?
    – Conrad C
    Commented Nov 28, 2012 at 1:43
  • I've also planted 8 seeds and only 1 grew out, which I find wierd, why do you think this happened?
    – Conrad C
    Commented Nov 28, 2012 at 1:45
  • Ordinary LEDs aren't going to help - you need to use, as I already said, 'grow lights', not just any old light source. The lack of growth will be caused by a combination of things, as mentioned in the answer. As for seed germination, given I don't know how old the seeds were or how you grew them, that's a tough one to answer, but sometimes, seeds just don't germinate.
    – Bamboo
    Commented Nov 28, 2012 at 12:57

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