Leaf shedding from tulip poplar

It’s late summer in the Southern Appalachian region (USDA zones 6 and 7). Outdoor temperatures continue to hit 90°F almost daily, and weekly precipitation is low. Over the past 3-4 weeks leaves have been dropping prematurely from landscape trees.

Tulip poplar (Liriodendron tulipifera), river birch (Betula nigra), willow (Salix spp.), sycamore (Platanus x acerifolia), elm (Ulmus spp.), hackberry (Celtis spp.) and redbud (Cercis canadensis) appear the worse offenders.

What these trees have in common, other than yellow fall color, is that growth is continuous from early spring thru late summer. Trees produce new leaves as long as air temperatures and soil moisture are favorable. Such trees abort excess foliage when environmental conditions become stressful.

Another way of stating: these species tend to overachieve, producing more leaves than they can support as environmental conditions turn negative. Under typical hot dry summer weather, they conserve through a dry patch by shedding leaves. The older interior foliage is typically the first to abort. Most summers all seven listed species lose leaves prematurely.

Bottom line: prematurely shedding leaves is very normal for these and some other landscape trees. Deep irrigating of trees reduces leaf loss, but is generally unnecessary. Leaf loss is a natural phenomena and is not detrimental.