Q: I planted tomatoes in a raised garden. I have dried grass clippings on top of the black biodegradable weed guard that covers the soil. I am using a 5 gallon bucket attached to a soaker hose for irrigation and fill it up 2 times a day, once in the morning and once in the afternoon. The leaves on the plants are curling. Am I watering too much or not enough?
A: Over- or under-watering is not the problem, it’s herbicide damage.
The grass clippings came from a lawn that was treated with broadleaf weed killer. Fumes from the clippings or irrigation water transporting chemicals to the tomato root zone are the proximate cause of damage.
Other causes of the same damage include spraying weedkiller nearby on a hot or windy day or using manure that came from an animal that grazed in a treated pasture.
Tomatoes are extremely sensitive to herbicides. The cupping, strapping and rolling of leaves and stems is exactly diagnostic for weed killer damage.
Just for curiosity, let a couple of the vines continue growing and see what happens. It’s possible that they will “grow through” the damage and produce fruit. I am not qualified to say whether the fruit is safe to eat but it would be interesting to see what happens.
see also Tomato Leaf Rolling