Watersprouts? Suckers?

The proper name for these small-diameter shoots along the trunk and major limbs of a tree is epicormic growth. We are often asked to prune these off for aesthetic reasons, and we will generally try to convince you otherwise, at least in the short term. Due to the recent drought, we are seeing exceptional quantities of epicormic growth.

Epicormic growth occurs in response to various stressors such as soil compaction, root damage, drought, or dramatic canopy loss from severe weather or over-pruning. Dormant buds in the trunk and limbs are activated by hormonal processes, and the resultant growth is typically rapid and vigorous, but weakly attached to the primary limb. If they are allowed to grow to a large size, epicorms can become hazardous due to this weak branch attachment.

On the other hand, epicorms serve an important function by quickly creating additional photosynthetic capacity and energy to the tree under stress.

We suggest identifying a tree's stressors and determining what can be done to mitigate them before removing epicormic growth. For example, a tree suffering from drought stress and showing a thin upper canopy will often produce abundant epicorms along the lower trunk and limbs. If drought conditions can be mitigated by providing adequate water and nutrients, the upper canopy may be restored. Once it is back to health, removal of epicorms may be reevaluated.