Tomato plants are very sensitive (a bit like some of us!) and any changes that happen suddenly or conditions that become unfavourable can stress them – and we all know what stress is like!

Positive Stress
This includes when roots reach the sides of a pot and realise that they only have so much room to grow. This has the effect of forcing them on to flowering and maturity. As long as they are potted up and don’t become root-bound, they won’t mind too much.

The technique of keeping plants in small pots to make them flower sooner, is called “forcing”. If over-applied will stunt growth and plants will produce a poor crop.

In contrast, a seed sown directly into the soil will have an unlimited area for its roots and will usually take longer to reach the fruiting stage – if it lives that long!

Negative Stress
There are many causes of this kind of stress, including:

  • Over-watering
  • Over-feeding
  • Being moved outdoors overnight before being hardened-off
  • Affected by diseases

Signs of Stress
Leaves that curl at the tips or turn away from the the sun are signals that something is wrong.

tomato curling leaves

This photo shows severe curling at the tip of a tall variety – the plant is either very stressed or suffering from a virus such as curlytop.

The cause of wilting leaves may just be a lack of water – but could be something more serious like a fungal infection that stops-up a plant’s plumbing.

Leaf roll – when leaves roll inwards at the edges is very common and some varieties will do this by default. This is nothing to worry about.

However, if leaves curl upwards at the edges, that is a sign of stress.

Leaf discolouration is usually due to nutrient deficiency. It is very common to see a purple tinge on the underside of leaves which indicates that temperatures are a bit low and it is therefore more difficult for plants to absorb nutrients.

It’s best not to feed at roots when treating plants for stress but give a foliar spray (misting) with a tonic of some kind.

Shade from direct sunlight and keep warm, dry and out of the wind.

After a few days – if the plant is still in a pot, pot on to bigger home and add perlite to the mix. This will help the roots by adding air to the soil.

Nutrients and tonics such as SP Plant Invigorator and Liquid Seaweed Extract help boost their general health.

There are a number of stress relievers and plant boosters (organic too) in the hydroponic product range that can be applied to soil-grown plants.

So even tomato plants can suffer from stress and their leaves will let you know when they need help!

9 Responses

  1. Bill
    | Reply

    I’m over 60 and never tried growing tomatoes. Recently I took in a foster child, 6 yo girl. She loves tomatoes and anything to do outside, so we bought several tomatoe plants at our local garden center. The plants did very well and grew fast. It’s been 4 months and while they grew very tall, over 7’, they still have yet to produce any fruit. My uneducated guess is they have/had bugs which ate many leaves, treated leaves with a spray, and secondly they are very stressed.

    We live in SW florida and it’s very hot and wet. I made the mistake of moving the plants under the roof overhang to keep them out of the rain and found the pots full of rain water one morning. So they were again moved. Ever since the plants have lost most of the foliage and are mostly empty vines.

    Is there something I can do to save over stressed tomatoes? I hate to start over but that might be the best decision. Any advice is appreciated.

    • Nick
      | Reply

      Hi Bill, if you have plenty of flowers on your plants then you should get tomatoes growing soon.
      Some varieties take a while to set their flowers which become the tomatoes. Lower leaves often get eaten by bugs and damaged, so this shouldn’t have much effect on the plants.
      Just to be on the safe side, I would grow a couple of extra plants too!

  2. allan
    | Reply


  3. allan
    | Reply

    i remember when i was young my grandfather growing alot if his toms like the way nick says the stem being buried but if i can mind it was in his glass house which was rather large from what i can mind 20 odd years ago he had high yields from this way but did also show alot as well
    iv just llost quite a few tomatoe plants of different varieties my wife was putting them in the polly tunnel in the morning and then bringing them back in as it went dark at the weekend she forgot about them next morning they didnt look to great iv managed to bring a few back to life but lost about five i was trying to harden off for planting out soon obviously not ready yet
    any advice greatfully received will the plants that have re-vived will these be ok for going into flower or am i better starting again
    thanks al

    • Nick
      | Reply

      Hi Al,
      They will probably revive – you’ll know within a week or two by the fresh new growth. Keep them as dry as possible and under-water rather than over-water.
      I would sow a few extra seeds just in case!

  4. Dave
    | Reply

    My Red Balconis are still in two inch pots. They are not growing but most of them appear healthy. Would you think I could leave these varieties in two inch pots until planting out?

    • Nick
      | Reply

      Hi Dave,
      They won’t be healthy for long in 2 inch pots – best to pot them on into 3.5 inch unless you can plant them in their final position in the next week or two. In the UK it’s the end of May to be sure there is no more frost.

      • Dave
        | Reply

        Thanks Nick, I’ve bunged them into larger pots and put them into a cloche where other seedlings have been for twenty days. They haven’t grown either but they have survived.

        I have an idea. In the wild , cordon tomatoes must run along the ground rooting themselves as they grow. They never get side shooted, but they must put down roots from the stems and leaves. I know that the fine hairs on the stem and leaves will become roots if they touch the ground, so I’m thinking of pinning a plant down like a strawberry runner. Is this a good idea? Will the plant develop a good root system and therefore a good yield of tomatoes? Will the tomatoes rot on the ground?

        • Nick
          | Reply

          Hi Dave,
          It’s an interesting idea … however, I think that the wild varieties would be of the bush type.
          If we run a cordon along the ground, I think, as you suggest, that the tomatoes would rot and get eaten by slugs and snails etc. There is a technique called “trenching” where the stem is buried beneath the soil to create more roots and give a plant more vigour – used when trying to grow a record breaker!

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