Why Do Some Trees Keep Their Dead Leaves?How to explain why beech and oak leaves persist

4 March 2026, by Lautenschläger/Ed.

Photo: University of Hamburg / Esfandiari

Many of you have probably seen this before, when walking through a bare deciduous forest in winter, suddenly there’s a tree with brown leaves clinging to it. This botanical phenomenon is called marcescence: Dead plant parts, such as leaves or flowers, do not fall off immediately but remain on the plant all winter. It is particularly evident in beech and oak trees. But why does this occur in some plants only? What’s behind it?

To investigate this, we are collaborating with the Loki Schmidt Garden, the University of Hamburg’s botanical garden, on 2 international projects that are jointly generating a large dataset. One project, headed by the Missouri Botanical Garden in St. Louis, USA, focuses on marcescence in woody plants and involves 18 botanical gardens in Europe, Asia, and North America. A project on marcescence in perennials originated from an initiative at Friedrich Schiller University Jena. This also involves several gardens. A large number of gardens not only improves the statistical reliability of the data but also allows for observing the phenomenon across different climate zones.

Protection against browsing or against frost and snow

Here in Hamburg, we draw on the extensive collection of more than 10,000 plant species at the Loki Schmidt Garden. Depending on the study design, different investigation methods are applied. For one project, for instance, we examined all woody plants in the garden—trees, shrubs, and even climbing plants—in winter to see if they still had any leaves left in January and, if so, how many. To do so, an altitude gradient is defined, meaning we consider at what plant height withered leaves persist. In the second project, we analyzed approximately 50 perennials, meaning hardy, herbaceous plants whose aboveground parts die in winter, and compared these surface parts from August and January.

As the seasons change from fall to winter and the first frosts occur, plants slow down their metabolism and normally shed their leaves. We want to find out why some plants exhibit this phenomenon and others do not. Is this a form of plant adaptation? Does it benefit the plant? Or is it an evolutionary remnant?  Several hypotheses pointing to possible reasons have been put forward: The dried-out, dead parts of the plant may provide protection against browsing or shield it from frost and snow. However, it could also be a deliberate and gradual return of nutrients—in other words, a kind of nutrient reserve that lies dormant in the dry leaves. 

The age of the trees makes a difference

We could establish that this phenomenon is more commonly observed in small, young trees than in old, large trees. Also, it is more likely to occur near the base of the trees than in the treetops. The colder and drier the climate where the plant is located, the more marcescence was observed in the respective species. 

The data from the first project on woody plants has already been analyzed and prepared for an international publication. The remaining data is being analyzed by a master’s student and correlated with factors such as soil values. Soon, we, the participating researchers, will engage in a discussion on this topic.

What I find particularly fascinating is that this phenomenon has even left a mark on some fairy tales. In The Legend of the Oak Leave, for instance, a poor farmhand promises his soul to the devil in exchange for money enabling him to marry his wealthy neighbor’s daughter. The servant stipulated one condition: “You’ll only get my soul when the oak tree we’re sitting under here has lost all its leaves!” But oaks do not shed their withered leaves in winter, and by the time the last brown leaves are falling from the trees in spring, new leaves are sprouting on the branches, so the oak is never bare.