Why do Some Trees keep Their Leaves with Winter?

By: Paul Kortebein

December 24, 2018

Category: Nature note


Above: Oak trees at Murphy-Hanrehan Park Reserve organize onto your leaves with winter. Picture by Erin Korsmo.

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At the end of fall, many deciduous trees shed their pipeline for the winter season. In fact, words deciduous comes indigenous the Latin indigenous decidere, which method to fall down or off. Over there are, however, a handful of deciduous trees around these parts that have actually a tendency to keep their leaves previous fall. It is an exciting phenomenon the is not completely understood. But before we acquire to that, let’s go v a few of the basics.

Why perform Trees lose Their leaves at All? 

As v most every little thing else in the natural world, tree behavior revolves about the sun. Once trees detect a reduction in the amount of daylight, they start to alleviate the lot of chlorophyll they produce. 

Chlorophyll, the course, is the colours that makes leaves green and also is the major producer of power for almost all plants. Once chlorophyll production stops, the gets broken down and taken back into the tree. This palliation in chlorophyll allows other pigments that have constantly been existing in leaves, however not visible because of the overwhelming amount of chlorophyll, come be seen (like yellows, oranges and reds).

Read more about why leaves change color in a previous blog post.

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Image from the public Library of Science.

To go in addition to this change in color, tree prepare to melted leaves by growing a great of cells in between the sheet stem and also the tree branch known as one abscission layer. This layer stops the transfer of nutrients and water to the leaf and also becomes the main physical factor trees lose their leaves. The abscission layer additionally helps defend this perceptible area that the tree from winter cold and also dryness. 

The main reason for leaf drop on many trees is that, come winter, it it s okay pretty cold and also dry in our component of the world. Quite than expend power to defend these fragile organs, trees burned leaves to maintain resources. 

The main difficulty is that water is essentially unavailable to most plants in the winter (because it’s ice), so over there is no way for them to replenish what they lose. And, as far as i know, over there is no revitalize and replenish lotion accessible for trees. 

But What about Trees the Don’t lose Their leaves in Winter?

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There space a handful of trees in our region that do hold onto your dry, brown pipeline throughout winter. The term because that this is “marcescence.” The abscission great on these trees does no completely kind until spring, which enables them to organize on to their leaves lot longer. 

Marcescence virtually always wake up on sexually immature components of the tree (parts that have actually not yet created flowers). Commonly, trees will certainly exhibit marcescence as soon as young, however lose this characteristic when they obtain older. Most of our oaks space finicky this way. 

It is additionally common for only a portion of a tree to retain leaves; commonly leaves will remain on the branches closest to the ground.

Here space some tree you may see exhibiting this behavior and also where friend can discover them in the Park District:

Swamp white oak: These trees space planted in picnic areas and also parking too many throughout the Park District.

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Hop-hornbeam/Ironwood (Ostrya virginiana): These tree are comparable to Carpinus, but much more common. They can be found in the understory the most forests within the Park District.

Is There any Benefit to keeping Leaves?

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There is no real consensus in the tree research community as to why part tree varieties keep your leaves, but there room a number of theories. The key one is that keeping leaves protects following year’s sprout from browsing deer or the drying winds that winter. 

Ultimately, marcescent trees lose their leaves come springtime as brand-new plant parts push the old leaves off the branches. So, either way you will have to rake pipeline – just not until the spring.