Some homeowners and commercial growers have reported fruit trees and other spring flowering trees and shrubs blooming and leafing out this fall instead of at the normal time in spring. Stresses such as drought or conversely too much water can cause growth to stop and start, confuse woody perennials and trigger out of sync bloom.
Dr. Barb Fair, Extension Horticulture Specialist and Assistant Professor at NC State University, believes the current unexpected blooming is likely a stress response related to the hurricane.
“Late winter and spring flowering trees and shrubs begin to develop new flower buds for the following year after they finish flowering and during the summer when they are in full leaf. There is a complex relationship between flowering response, plant hormones and plant chemistry. Day length and temperature play an important role in when plants flower in general, and when seasons change plants respond by altering their internal chemistry and hormone levels. This is normal, but when storms come through and change the conditions directly around the plant, it can trigger an unusual response such as plants blooming out of season. The storm can lead to stress which leads to a change in the plant’s hormone levels and chemistry. Thus, plants bloom at strange times and may even produce leaves where others were lost.”
It is rather complicated and no one factor seems to explain it. As with most issues with plants, it is usually a suite of factors that play into a plant’s response to stress. In some fruit trees, flower buds are formed in mid-summer for next year’s crop. All buds start out as leaf buds but some convert to fruit buds, a process called floral initiation. This process is irreversible since flower buds cannot revert back to leaf buds. The timing of floral initiation differs for the various types of fruit and varies a little from year to year, depending on the conditions. Normally, the initial development of the flowers within the buds is completed before the tree enters dormancy in late fall. This can be brought on by drought or the short days and cool temperatures of fall. Later, internal factors limit growth even when conditions are good for growth.
It is unlikely the trees will bloom again in the spring. They may have a few blossoms left over after this flush, but blooming will be much diminished, if at all. There should be no problem when it comes to developing new leaf buds and leafing out in the spring/early summer, but they are using some of those pre-formed leaf buds as well now, and so you might see some regrowth, late leaf flushing, or reduced leaves at the beginning of the season. If the trees are otherwise healthy, there should be no long-term effect on the production of new leaves. Callery pear is one of the toughest plants in the landscape and should be fine despite the hurricane’s effects.
Minda Daughtry is Horticulture Agent with North Carolina Cooperative Extension in Lee County.