Evergreen trees, like pines and conifers, do not lose their foliage in the winter. Deciduous trees, on the other hand, DO shed their leaves, only to regrow them in the spring. And although this is the expected order of Mother Nature, there are circumstances in which a deciduous tree might retain its dead leaves throughout the course of the winter. In these cases, the leaves will turn brown and die as the season changes, but they will not drop unless they are dislodged by a heavy force (i.e. wind, storms, felling, etc.).
If you have noticed that your deciduous tree has not shed its dead leaves, do not worry. In many cases, this occurrence is not fatal for trees. It can, however, be damaging to its branches and limbs overtime. Continue reading to learn what this leaf retention effect is, which trees are commonly affected, and what you can do to help prevent it from happening to your landscaping trees.
Leaf Retention in Deciduous Trees
When a deciduous tree fails to shed their dead leaves once the season turns into winter, it is likely due to the occurrence known as marcescence. Leaf marcescence generally affects young or newly planted trees, but it can also affect a wide range of trees (and plants) in various stages of growth and condition. For young trees, the occurrence often goes away as they mature. There are many theories on what causes marcescence in trees, but none have yet to be empirically proven. The most accepted theories in the industry are: 1) marcescence is caused by the premature closing of the abscission layer, or 2) the interruption or delay of abscission layer development.
Trees have an internal vascular system that distributes water and nutrients up through the tree and to the leaves. In the fall, the veins within this internal vascular system gradually becomes narrower, and eventually, the veins close up entirely after the abscission layer forms inside them. Once the abscission layer has formed, the tree can shed its dead leaves for the winter.
With this understanding, you can see how the two above-mentioned theories could be true. If an outside influence causes a tree’s abscission layer to prematurely close, delay development, not finish development, or not develop at all, it could cause leaf marcescence. Examples of such influences may include wildlife interference, pest infestations, construction damages, drought, early freezes, and more.
Types of Plants and Trees Affected:
🍂 Oak Trees (Quercus)
🍂 Hornbeam Trees (Carpinus)
🍂 Frailejone Trees (Espeletia)
🍂 Beech Trees (Fagus)
🍂 Witch Hazel Trees (Hamamelis)