With fall approaching (or already upon us?), trees are making their last minute deposits of starch and getting ready to drop their leaves. While the first signs of the impending winter are just starting to paint our hillsides, the trees have quietly been making preparations for the last 3 months. Winter buds, for example, contain the leaves that will sprout this coming spring. These are produced and have been laying dormant since mid-summer in most species.
There are two big advantages to creating buds for next year in mid-summer. The first is that energetically, next year’s growth is already paid for (primarily by starches stored from the previous year) as summer insects emerge and conditions turn hot and dry. Even if the tree loses all of its leaves to hungry caterpillars (as with the oaks this summer), they won’t be any farther behind in preparing for winter. Compare this to fruits and nuts, which ripen in the fall (red oak acorns take 2 years to mature). In any given year, reproduction is essentially a bonus activity. In the wake of a stressful summer, a stressed tree can halt production of fruits. I’ve been on an apple kick and noticed that hard hit apples were nearly barren this year while those that escaped the caterpillars have been incredibly productive.
The second advantage is that in a pinch, the buds from this year can be coopted to produce new leaves in the summer to recover from damage. And this is exactly what happened with our oaks.