Growing Tomatoes in Hot weather

Tomato plants love warm weather but only some like it hot!

Here are some of the symptoms that show on varieties that prefer more moderate temperatures.

  • Leaf roll and leaves turning away from the sun.
  • Top leaves cupped and smaller than usual.
  • Tip of plants wilting.
  • Sun scald, greenback and blotchy ripening on fruit.
  • Flowers may fail to pollinate owing to dry air conditions resulting in blossom drop.

Measures to take…..

Increase Air Circulation
De-leaf lower branches to reduce water requirements and improve air circulation

Keep Roots Cool
When the ground surface, such as patio slabs, gets hot pour water on it to lower the temperature and increase the air humidity to help flowers set.

Garden Pearl Tomato
Garden Pearl – off to a good start with plenty of flowers setting fruit.

Large black pots in direct sunlight can get very hot and the roots inside dry out fast. Plant may also become stressed – usually displayed in curled leaves. Stick white plastic or even paper to the front of the pots to reflect the heat/light.

Garden Fleece
Shade cloth such as garden fleece can be hung between the sun and the plants to make the direct sunlight more diffused.

Coolglass can be applied to greenhouse glass – it’s similar to the old windolene cream that stopped people looking through a window.

Foliar Spraying Helps
It’s best not to spray with water in direct sunlight but in the morning and evening when it’s cooler, a foliar spray will be alright. This would be a good time to add some calcium to the water in the form of Chempak calcium or even milk – mix 50/50 with water and expect your greenhouse to smell like a dairy!

It’s best not to over feed in hot weather – plants need plenty of water rather than a heavy meal.

Light, Heat and Hot Varieties
I once saved a few seeds from a market bought tomato when on holiday in Malta.

The seeds germinated and the plants grew well back here in the UK, but I had more foliage than expected and very few flowers. This shows that varieties that are used to growing in hot local conditions need both light and heat to flower and set successfully.

A few of those seeds would do well in this hot weather we’re having!

Water Access
The Quadgrow Planter with its own reservoir and the Autopot System with its automatic watering valve are ideal in hot weather.

When plants have constant access to water they won’t become stressed and tomato split is much less likely as soil is never allowed to become too dry.

Flower Pollen and Flower Set
Tomato flower pollen is very fine and when the air is the right humidity – not too dry and not too wet, flowers should set with a little help.

tomato flower

In order to encourage pollen to enter the stigma, travel down the pistil and into the ovary at the bottom, it’s important to send it air-borne within the anther cone – where the pollen is made.

Bees produce vibrations from their wings that moves pollen from the anther into the stigma, but as already mentioned, the pollen has to be in the right state – not too moist or dry – to be affective.

Also, the length of the stigma varies within the anther cone and some varieties find it more difficult to set than others. On some varieties the stigma sticks out the top of the anther cone.

In high temperatures I would suggest that mid to late morning is a good time to shake, tap vibrate or use an artist’s watercolour brush to gently move the pollen around inside the anther cone.

More about tomato flower set.

I hope your tomato plants are coping in this hot weather!