Tomato leaf roll

also called Physiological leaf roll

Tomato leaves curling upward into tubes on a plant that is otherwise dark green and cropping well. It is benign, it is common, and it needs nothing.

Disorder Disfiguring Doesn't spread

What you'll see

Older, lower leaves rolling upward and inward along the midrib until they form thick leathery tubes.
The rolled leaves staying dark green, firm and healthy, with normal color and no mottling.
The growing tip and the youngest leaves flat and normal — the detail that separates this from a virus.
The plant flowering and fruiting normally throughout.
Rolling worst on vigorous, heavily pruned indeterminate plants after a wet spell or a hard watering.

Why it happens

The plant is storing more carbohydrate in the leaf than it can move out of it, and the leaf thickens and rolls. It happens when the roots take up more than the top can use — after heavy watering, in cool wet weather, on a plant with a small fruit load, or when hard pruning has removed the tissue that would have used the sugars. It is a plumbing problem, not a disease.

Heavy or erratic watering, cool wet weather, transplant root damage, and severe pruning of indeterminate tomatoes. Some cultivars roll every year regardless.

Treating it

Nothing. This is genuinely benign and the plant will crop as well as it would have anyway.
Water more evenly and less heavily if you want to reduce it, and mulch.
Prune and pinch out less severely.
Look at the growing tip before you worry: if the new growth is flat and green, it is this and not a virus.
Rule out herbicide damage, which twists and cups the new growth instead, and curly top virus, which yellows and stunts.

Keeping it away

Water steadily rather than letting the plant dry out and then soaking it.
Mulch to even out soil moisture.
Take side shoots out while small rather than removing large stems.
Improve drainage in a bed that stays wet.
Choose cultivars that do not do it if the look bothers you; it runs strongly in some lines.

Who gets it

Tomatoes above all; potatoes and occasionally peppers do the same thing.