Epicormic sprouts, also known as “suckers” or “water sprouts”, are growth that emerge from dormant buds along the trunk and branches of a tree. Some species of tree produce a large quantity of these sprouts such as a Live oak (Quercus virginiana), wheras others such as a Sycamore (Platanus occidentalis) will produce comparatively very few.
The sprouts may appear for a variety of reasons, mostly on parts of a tree that are newly exposed to sunlight but in urban areas are often a symptom of stress in a tree. Trees that have suffered storm related damage or that have been overly pruned and thinned will grow epicormic sprouts to compensate for the loss of leaf surface.
A commom practice, to “improve” the aesthetics of the tree, is to remove this growth either partially or completely to the tips of the branches, referred to in arboriculture as” lion-tailing”. This causes stress in the tree for many different reasons. The tree grows these sprouts first and foremost when there is a need to increase amounts of photosynthesis, and it does require a lot energy and resources to generate the growth. These sprouts also serve the purpose of protecting bark that is directly exposed to sunlight by providing shade for it. Sun scald is a common cause of decline in trees in Texas. With continuous exposure to the sun the bark will begin to crack, exposing the vascular system and making it vulnerable to entry of pests which will accelerate the decay of the wood, making the branch vulnerable to breakage. Lion-tailed branches also have a very high tendency to break under heavy winds as the sail, or leaves, are all on the tip instead of being spread out along the branch where it can better deal with wind pressure. When an epicormic sprout is well developed it also offers the arborist an option of pruning back to it in case the tip of the brach has died or broken, preserving more of the branch and decreasing the amount of stress and wounding that would happen if the whole stem had to be removed back at the trunk.
It’s worth adding that when epicormic sprouts are removed, it triggers more of them to grow as the tree will need more photosynthetic tissue to compensate for the wounding, thus defeating the purpose of removing them in the first place. The best practice is to remove a small percentage of the weaker ones that are growing in undesirable places such as by major branch unions or over a structure, and allowing the rest to develop and self regulate. Some sprouts will become more dominant, shading out others and eventually turning into tissue that will resemble a branch.