Tomato Trouble

I don’t think there is a gardener alive who hasn’t though “I wonder whats wrong with this plant?”

It could have been to do with a sickly over watered orchid, or a dry cherry tree thats dropped all its fruit.  However, because I’ve got a new polytunnel,  I wanted to concentrate on tomatoes.


I’ve been doing a little research about afflictions that these gorgeous fruit can suffer from (incase you didn’t know, tomatoes are actually a fruit, not a veg).  There are certain ailments that are more common, and some are easier to deal with than others.

One of the commonest problems at this time of the year is temperature.  Not just how warm it can get in the greenhouse or tunnel in the day, but how cold it can get at night too.

If you find that the leaves on your plants are starting to curl, that’s usually down to cold night time temperatures.  Try and keep it around 15 degrees if possible.  If you don’t have a heater you need to think outside the box.  I’ve placed black material in my tunnel to try and soak up some of the heat from the sun.  I also have a pile of bricks to do the same job, they release the heat back during the night.  It’s the same principle as night storage heaters.

If you find that your plants are starting to go a blue/green/purple colour, thats usually down to low growing temperatures too.  This can be at night or during the day.  Try and keep daytime temperatures above 21 degrees.  This may mean not opening the door to your greenhouse fully.  However, remember you still need ventilation, or you will create a whole new set of problems.

When your fruit start to grow, if you experience ‘cat facing’ or deformities, this is another result of cooler temperatures.  This normally happens at the beginning of the season with the plants first tomatoes.  It won’t affect the taste of your fruit, its just annoying and unattractive.



Higher temperatures can also affect your plants and fruit.  Heres what you need to look out for.

If your plants have stretched stems that are yellowish/green and have browning on the leaves (especially the tips), this is a good sign that the temperature is getting too hot.  Try to ventilate more, or spray water on the floor of the tunnel/greenhouse to ‘damp it down’, this will lower the temperature.


Other causes of this condition are too much nitrogen in the plants food and low humidity.

We’ve already discussed the humidity, as damping the area down will increase the humidity.

If you suspect that you are feeding your tomatoes too much nitrogen, stop!  And when the plant starts to produce its first tomatoes, you should be feeding it with potassium enriched food (tomato food).  This will increase the yield of fruit.

Make sure to follow instructions on your chosen fertiliser.  It’s normally acceptable to feed plants every 2 weeks, however follow what the packet says.

If you do feed the plants too much, you’ll probably see that the leaves go very dark green and start to curl, plus the leaves can start to brown.  Simply flush the tomatoes through with lots of water and don’t feed them too much in future.


A less common condition, but still problematic, is magnesium deficiency.  This could be because you’re using a poor compost, or the variety of tomato you are growing needs more magnesium than others.  Plants will usually have yellow mottling on the older leaves and this may turn brown.

The remedy I’ve found for this, was in my grandad’s old garden book.  Simply mix 1/2 oz of epson salts (available at the chemist) in a pint of water and spray the plants twice at fortnightly intervals.  This should start to resolve the problem, at least thats what my grandad says.


Yellow lower leaves that don’t disappear when you feed your plants, can be a result of too little, or too much water.  Dig down by the rootball to see if the plant is water logged or bone dry, then you’ll know how to remedy this problem.


When it comes to picking your fruit, if the tomatoes are split or cracked, it’s due to inconsistent watering.  This is normally when a plant is really dry, then receives lots of water.  The fruit try and suck up as much water as they can, but they can’t grow quick enough to cope, thus, they split and crack.  Make sure to water the plants more consistently, or not as much water all in one go.


When it comes down to it, problems with tomatoes are usually resolved with good watering/feeding and good temperature control.

Finally, please don’t be put off growing tomatoes.  They are easy to grow and really will reward you with lots of tasty fruit.  This is just a short guide to help you fight any problems that may arise.





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