Hi Tree Friends,
Well these past few weeks has added to the crazy weather stories of 2019.
I have been asked ‘Where did fall go?’ … Well the answer is … Don’t blink, it just went past.
The other questions are ‘Why are the trees holding leaves, and is this a problem?’… That answer is below…
‘Why are the trees holding leaves, and is this a problem?’
Marcescence, the term used to describe leaf retention, or trees holding leaves. In a ‘normal’ fall; this is common with oak, American beech, Witch Hazel, Hornbeam, and Hophornbeam trees.
In a ‘normal’ fall season deciduous trees and conifer trees prepare to shed their leafy summer coats/leaves, the cells at the interface between the twig and the end of the leaf stem release enzymes and form an abscission layer that “unglues” the leaf/needle. This separates the leaf/needle from the vascular bundles, allowing it to fall free. All trees shed leaves/needles every fall. Conifers generally retain their needles for more than one year, and drop/shed approximately 1/3 of the needles.
What we are seeing is early cold weather or frosts may interrupt the abscission process or “kill” leaves quickly. In these cases, the occurrence of marcescent leaves may increase.
Marcescent leaves are often more common with smaller trees or more apparent on lower branches of larger trees. In the case of smaller trees, which in forest conditions would be growing beneath taller trees, the reduced sunlight might slow the abscission process. By doing this, the understory tree leaves and the leaves on lower branches of larger trees would also have the opportunity to continue or even increase their photosynthetic process as upper leaves fall. Then, perhaps, leaves lower in the canopy are “caught” with cold temperatures and their leaves hang on.
The cold temperatures did not release the leaves or stopped the abscission process. Then the wet snow started to fall, held onto the braches and leaves; compounding the weight; and resulted in many broke limbs.
The record cold temperatures this week should not pose long term damage to the trees. We might see a little tip dieback on a few trees with smaller weak buds. Hopefully more leaves will drop, as we have been seeing more broke limbs at the ends of the branches.
This has been another ‘record week’ of excitement for our GreenTeam friends. The municipalities need the same trucks to plow, salt and pick up leaves…. All at the same time. The landscapers have not placed the snow stakes, need to plow, and complete the fall clean ups.
Please say thank you to the Municipalities and the landscapers, as their crews need a ‘pat on the back.’
-M.D. Skeet, Commercial Arborist Representative at Bartlett Tree Experts