Bumps and growths or adventitious roots on tomato stems
Tomato plants, particularly heirloom varieties, and tomatillos may produce small growths with short, fleshy, bristles. These are adventitious roots or aerial roots that would grow into normal roots if placed in contact with the soil. But in many cases, they can appear higher up on the stem.
The degree to which a gardener will see this is determined by cultivar, weather conditions, and culture.
Adventitious roots are normal bumps and swellings on stems
Small knobs, swellings, or bumps on stems are usually harmless and caused by plant genetics (natural growth) or stressors in the environment. Pepper, tomato, and rosemary plants often exhibit such growths. No action needs to be taken.