Tomato stems sometimes develop “warts” or “bumps” on the stems close to ground level. Though this looks abnormal, the condition is natural and not harmful. These bumps can eventually give rise to roots (called adventitious roots) if conditions are favorable. This is actually the mechanism the plant uses to form roots when tall, leggy plants are planted in a trench. Some varieties tend to be more prone to this condition than others and stress such as that produced by waterlogged soils also makes a “warty” stem more likely. Growth regulator type herbicides such as 2,4-D can also induce this state. So if you see a warty stem, don’t be concerned. The bumps will not harm the plant in the least. (Ward Upham)
