Tomato Leaf Roll and Stress

Many problems aren’t life threatening to a plant although they may result in a reduced crop – tomato leaf roll is one of them.

They say that a tomato grower with poor eyesight sleeps better at night! It’s easy to find worrying looking marks on just about any tomato plant if you look closely enough.

Tomato Leaf Roll

One of the biggest issues at the moment is leaf roll.

Tomato Leaf Roll
Leaf Roll


Tomato Leaf Roll
Leaf Roll

Some varieties roll some of their lower leaves by default, but in high temperatures, leaf roll, leaf cupping and leaf curl are highly likely to occur on most plants – especially those grown in containers and grow bags with limited resources.

By reducing water and heat stress, leaf roll and a number of other issues can be kept under control.

Watering – water stress
The challenge here is to provide water 24/7. The problem is that plants absorb different amounts of water each day, depending on the growing conditions … temperatures, light levels, humidity and air flow all effect the amount of water a plant needs.

The only way we can ensure that water is available whenever a plant needs it, without over watering, is by using an auto watering valve or a reservoir system.

Heat – heat stress
When light and temperature levels are high, plants will do everything they can to protect themselves from running out of moisture and wilting.

This includes diverting moisture from swelling fruit to leaves, which may result in Blossom End Rot.
Not only do plants curl their leaves in a number of ways, but they sometimes turn their leaves away from the sun and face them in another direction!

Tomato Taste
It may seem that when growing tomatoes, we are always battling something – especially the weather!
Too cold, too hot and not enough light to name just a few of the regular challenges we face from season to season.

However, no two seasons are the same and that includes variations in the taste and sweetness of each variety.

The amount of light the leaves receive and absorb has an effect on the taste.
The darker the leaves, the more light they absorb and a good reason to apply magnesium by foliar spraying when light levels are low during long periods of dull weather (magnesium darkens the leaf colour).

If the lower half of a plant’s leaves are tightly curled, it will have an effect on the taste of the tomatoes on the lower trusses because sugar production in the leaves will be reduced.

High temperatures can also reduce the sweetness of the fruit when respiration (which uses leaf sugars) overtakes photosynthesis (makes leaf sugars) and the plant uses more energy than it makes.

Over Watering
Over watering too can reduce the amount of nutrients plants receive which can also effect the taste.

You will also find that the acid content of tomatoes is a little higher in the earlier part of the season.

Miracle Gro

Organic Feeding
Over the past few seasons I’ve been using organic feeds on some of my plants. One make that I’ve found produces good results is “Miracle Gro” Grow Your Own Fruit and Vegetable Concentrated Plant Food – Organic Choice .

It’s a lovely thick dark mixture of chemical free organic nutrients (NPK 3-2-6). Give the container a good shake each time you use it to avoid lumps forming in the bottom. Using in conjunction with liquid seaweed makes a great organic duo of feed and booster.

The way to feed
There are many options for feeding organically but whatever you use, it’s important to feed little and often to encourage and retain good soil microbe activity. Also, the more air/oxygen that can be added to a liquid feed by shaking the better. Pouring one watering can into another (or similar) will add oxygen that will encourage soil activity, root health and rapid growth.

That’s about it for this week – if your plants are struggling with the heat, don’t forget to use shade cloth such as garden fleece, remove unnecessary leaf branches (see pruning) and cover black pots in direct sunlight with white card, paper or plastic to keep the temperature of the roots down.

It’s all go – but it’s good to have a sunny season!





4 Responses

  1. Rob

    Hi Nick, Re: Cherry Tomatoes and BER.

    For the last four years, I have grown Floridity alongside eight other varieties of cherry tom. Each year, I have lost one-third of my crop of Floridity through BER whereas all other varieties have remained clear. I have to conclude Floridity is a variety of cherry tom that is especially prone to BER. Hope this helps someone.

    • Nick

      Hi Rob, plum shaped tomatoes usually have more flesh than round toms at about the same size, and as you say, more prone to BER. I once grew a variety named Yellow Pear where every tomato was affected by BER!

  2. Nick

    Hi Valerie, remove all leaf branches up to the first truss, remove leaf branches at the back of the plants that are in the shade, remove the middle leaf branch where there are three between trusses and trim any leaf branches that are too long and interfering with the plant next door. Reduce any nitrogen feed and increase potassium feed (if possible). Hopefully the tomatoes will start to grow it bit bigger with less leaves.

  3. Valerie

    Good Morning Nick,Your newsletter as usual is very welcome.I am growing my toms in SIPs for the first time,Autopots and Quadgrows.I have followed directions very carefully and seem to have grown a forest of triffids! The stems are thick,the leaves large,flowers and fruit are appearing BUT they are too tall! They have reached the roof of my GHs,one small and shady,one larger and sunny! I am finding impossible to support them,especially in the small GH.Not all have made four trusses.Can I cut the back?
    The watering regime is certainly easier but I seem to have very thirsty plants.I feel that the recommended feeding regime is too high and have cut back but will spray with Epsom Salts.
    Next year I shall have to try shorter varieties.This year it is Gardeners Delight,Moneymaker,Black Cherry and golden Sunrise all grown previously in the normal way.