Normal Leaf drop
Usually, older leaves throughout the plant turn yellow to straw colored, then drop. The plants may look as if in decline but will fill up with new green leaves as new growth continues. The change in coloration is always the clue!
A gradual color change progression is normal in natural leaf shedding
Several common landscape trees and shrubs have physical or physiological traits that resemble a disorder but in fact they are fine ! Leaf shedding (senescence) and leaf retention (marcescens) many times cause confusion because we don’t see them as common or they are seemingly out of season.
Natural leaf shedding is often mistaken for a disorder in evergreens. Depending on the species, evergreen leaves live for one to several years, shed at different seasons, and shed influenced by environmental factors. Arborvitae in spring and summer. Magnolia usually in summer, and Pines and Cedars in fall.
Arborvitae drop their older leaves in Spring and Summer
Pines drop their needles in the fall
Fall leaf retention in deciduous trees is normal only for some oak species and occasionally beech. These are considered evolutionary adaptations that actually benefit the trees. Take a look under an oak tree covered in retained leaves – what you see is lots of bird poop on the ground – fertilizer! Birds tend to congregate in Oak trees that have densely retained their leaves.
There are also botanists that believe the leaf retention is to deter browsing animals to eat small twigs and branches if these are covered in dead leaves. Some think the retention is due to poor soil conditions. I myself like the bird poop theory !
Beech tree will many times retain its foliage
Marcescens on any other species is considered an abiotic disorder (abnormal) and is usually water deficient related. Sometimes also caused by sudden freezes or a disease that suddenly kills off a branch.
Taxus suffering from fungal root rot looses the ability to uptake water and dries out!
An extreme and quick water loss (it dried out!) will cause the same look on any tree or shrub during the growing season. In essence, the leaf died and got stuck on the branch before the natural process of leaf dropping occurred. The natural process of leaf dropping never had a chance to start !
Late spring freeze damage new growth which remains stuck on the branch
If your leaves are dropping out of season – Call Plant Specialists TODAY !
Our Plant Health Care Team can check them out for you !
Don’t delay – the sooner the better !
GREENING NEW YORK FOR OVER 51 YEARS !
Article written by our Staff Horticulturist, Peter B Morris, BSc, MSc, MBA
All photographs used with permission @SHUTTERSTOCK