Tomato plants have curled leaves and bumps on stems

by Diane
(Laurence Harbor, NJ USA)

Q. Can you tell me what to do to remedy my tomato plant's curling leaves and white bumps on its stem? It has been very hot and dry here and this plant has been watered daily, otherwise it droops and withers. It is planted alone in a large garden pot with good soil and is on an outside deck. It has several tomatoes on it, but I fear they will not make it.

A. You've got three issues going on. At least two of them can be related: bumps on stems and leaf curling.

1. Bumps on stems. The bumps on the stem are likely root initials. They are the earliest stage of development of a tomato’s roots.

Most of the time, bumps are not harmful to tomato plants and are considered normal. Root initials emerge on a tomato stem as a result of stress – most often when there’s a limit or blockage in the stem. Bottom line: the blockage is caused by over-watering, poor drainage, humidity, disease, or root damage.

When root initials make contact the soil, they will grow. Mound compost or top soil around root initials on the lower part of the plant. They will develop into full-blown roots, strengthening the plant’s root system.

Learn more about root initials.

2. Curling leaves
Root initials on your plant's stem combined with curled leaves at the tops and the branch ends can indicate exposure to an herbicide.

Herbicide effects mimic the plant hormone auxin and can also cause abnormal stem growth and leaf distortion.

If your tomato patch is near your yard or a neighbor’s, perhaps a weed-and-feed product, weed control, or other herbicide was applied and drifted. Mist often affects tomato plants.

The good news is that tomato plants can withstand a herbicide injury and often outgrow it when exposure stops. So if you (or a neighbor) have been spraying with Round Up either nearby or when there's a breeze - and stop - the curling should stop soon.

3. The heat and containers
Even though you're watering faithfully, tomatoes can easily get stressed in containers. In hot weather, set folding chairs over plants in midday. Or move containers to the shade during the hottest hours of the day.

Good Luck and Happy Gardening!
Your friends at Tomato Dirt