On a visit to the Pacific Northwest, I drove through patchworks of old growth forests and clearcuts. In the harvested areas, foresters have left clumps of mature trees standing for wildlife habitat and seed sources.
On those isolated trees, I noticed clusters of fresh green shoots sprouting directly from the lower trunks — a growth form that doesn’t exist in intact forests.
These are called epicormic shoots: new growth that arises from buds that are hidden beneath the bark.
Now, under normal conditions, trees grow upward and outward from buds located at the branch tips in the crown, where sunlight is most abundant.
But sometimes, the bark can grow over them, creating buds that remain dormant, sometimes for years, even decades. They grow just enough each year to remain under the bark as the trunk slowly increases in diameter.
And, when a disturbance occurs that removes nearby trees — like a clearcut, fire, or windstorm — the trunk is flooded with light. Then those long-dormant buds push outward, forming new shoots and rebuilding foliage.
The ability to make epicormic shoots varies among trees. Many pines can’t grow this way, so severe crown fires can be fatal to them. But Douglas-fir and redwoods can produce these new branches after injury, helping them to survive disturbance.
Epicormic shoots are a quiet reminder that beneath their bark, trees hold tiny insurance policies in an uncertain world.
