THE CAUSE OF AERIAL ROOTS ON GREENHOUSE TOMATO PLANTS

Bumps on tomato stems begin as tiny hairs on the stalk of the plant and are not necessarily a cause for concern. When surrounded by soil, these hair bumps quickly develop into roots (rather handy if the plant sprawls along the ground or tumbles from its supports). However, when the hairs grow into above-ground roots (called adventitious roots or stem primordials), it can be a sign of serious plant stress. The roots in this case are, in fact, a signal that a branch-tip hormone known as ‘auxin’ cannot move freely around the plant and is trapped in the stem. The stress, which is the issue, can be caused by several problems, including overwatering and high humidity.