"Why are the leaves on my tomato plant curling?" By Jim Hole

The passion that gardeners have for their tomatoes never ceases to amaze me.
This week we had over 450 people respond to our Hole’s Happenings Reader’s Choice questionnaire, and the most requested question by far was: “Why are my tomato leaves curling up?”
Well, the good news is that tomato leaf curl is not a serious problem…usually.
These are the 3 main reasons why tomato leaves curl:
First, some tomato varieties naturally have a bit of a twisting or curling growth habit. Typically, once the leaves expand, they tend to flatten and develop a more ‘planar’ growth habit.

Secondly – and most commonly – tomato leaves will often cup upwards due to an imbalance between roots and above ground growth. The cupping is referred to as physiological leaf roll, which is just a fancy term for the fact that the tomato roots cannot supply enough water to all of the leaves, stems and fruit. When tomato leaves sense a deficit of water, they respond by cupping upward to reduce exposure to sunlight which therefore reduces moisture loss.

Anytime the roots are not functioning well due to, say, restricted root space like a small pot, or if the roots are damaged, the leaves often roll. Vigorous hanging basket tomatoes are notorious for leaf roll because the ratio of leaves to roots is often large and the roots simply can’t keep up.

The good news with leaf roll is that it doesn’t cause extensive harm to the plant. And if you do your best to provide a good growing environment for your tomato plants, leaf roll can be kept to a minimum. But, keep in mind that rolled leaves won’t unfurl.

The third major cause of leaf roll is much more serious. It results from the misapplication of certain types of herbicides. The rolling of leaves from herbicide damage is different from physiological leaf roll. Herbicide damage is most prominent in the new growing points resulting in severe cupping, distortion and clumping of flowers and shoots. The source of herbicide contamination is often from misapplication of lawn herbicides or contaminated potting and garden soil mixtures. If you have herbicide damage like this the only solution is to get rid of the affected plants and soil and start over.

Every year, I receive dozens of tomato plants displaying herbicide damage. Often the herbicide damage wasn’t caused through misapplication by the owner of the tomatoes. The problem is, all too often, potting mixtures that have been blended with herbicide contaminated manure.

This is why starting with good quality potting soil is essential. Every bag of Jim Hole's Potting Soil and Sea Soil has been tested for quality-assurance.

And remember to feed your tomato plants too!

If you have a hanging basket tomato don’t forget to feed it! Of all the plants in our greenhouses, hanging basket tomatoes are the heaviest feeders. If you want to keep the feeding simple, add some Garden Pro Granular Tomato Food (5-10-15 + 3% Calcium) to each basket. If you prefer the liquid fertilizers, weekly applications of Nature’s Source (10-4-3) and Garden Pro Liquid Tomato Food (9-11-11) are a good choice. Find all your tomato plant needs at Hole's.

- Jim Hole