Now that the Autumnal Equinox has arrived, it is a good time to look back on this year in the Lives of Trees. For Eastern North America, this has been a great year to be a tree. Temperatures were mild to moderate for most of the growing season, soil moisture was adequate to above average, rainfall was well spaced. Although I have only been looking carefully at trees for a fraction of the lifetime of the average tree, I don’t remember a better growing season.
What have you seen this summer? Have you noticed young leaves on trees in your neighborhood in mid to late summer? Here in Kentucky, even though autumn is upon us, some trees still bear those very young tender leaves.
Have a look at these trees, and scroll down for more details
What we are seeing in these pictures is late-season growth. You may think that trees grow all summer long, but that is almost never the case. Trees are extremely risk-averse. Young leaves are vulnerable to frost, drought, insects and diseases that do not much bother mature leaves. Most trees in eastern North America open their buds in the spring, produce a quick flush of growth and then quickly stop. In a good year, a bud may form in May or June, the tree will rest for a while and then growth will resume. This creates a second flush of growth, as you can see in the young leaves in the pictures.
In a rare and exceptional year, you may see 3 flushes of growth. This is the first year that I have ever seen a third flush of growth on trees throughout the region. There are some slow-growing trees, such as bur oak, for which it is rare to see a second flush, let alone a third.
In the next part, I’ll explain some of the interesting details of this growth pattern.