Which trees keep their dried leaves throughout the winter?

Fagus grandifolia

American Beech in winter

A winter walk through a woods in Michigan will reveal deciduous trees holding their dried leaves from last fall. Marcescence is the technical term for plant parts that wither but do not fall off. It can refer to leaves, flowers, or fruit. In deciduous leaves an abscission layer forms at the base of the petiole (leaf stem). In most deciduous leaves the abscission layer hardens on the twig side in the fall, the leaves drop-off, and this layer protects the bud-scar on the twig. In marcescent leaves, the abscission layer does not function until buds break in the spring. Andrew Hipp at The Morton Arboretum explains this in greater detail.

Some species are more marcescent than others. Oaks, Beeches, Hornbeams, and Hop-hornbeams commonly hold their leaves. Younger trees exhibit marcesence more often than mature trees. Stress from drought or disease can cause marcescence in any deciduous species .

The color of the winter leaves is normally distinctive but hard to describe. With a little practice you can learn to identify these trees at a distance. Of course, looking at the shape of the leaf, winter bud, or the bark can confirm your identification.

Fagus grandifolia

American Beech leaves in winter

Marcescent leaves on American Beech (Fagus grandifolia) bleach from tan to a ghostly cream-color during the winter. Looking closely at a twig you will see long buds that confirm the identification.

Ostrya virginiana

Hop-Hornbeam leaves and winter bud

Hop-hornbeam (Ostrya virginiana)  has winter leaves that tend to curl. Once again, with practice the color is distinctive. Blue-beech or Hornbeam (Carpinus caroliniana) is similar to Hop-hornbeam but with lighter brown leaves.

Carpinus caroliniana

Blue-beech winter leaves

Oaks (Quercus spp.), especially the Black Oak group (subg. Erythrobalanus), tend to hold their leaves. Some years ago, when Dr. Warren Wagner was studying Shingle Oak (Quercus imbricaria) we learned to identify the species when we drove by. Shingle Oak leaves are tan or “potato-brown color.” Other oak species have a darker, reddish-brown color. Shingle Oak is Michigan’s only simple-leaved oak. Its leaves look more like bay leaves than what we in the north think a “typical” oak leaf should resemble.

Shingle Oak – L                                                                     Pin Oak – R

It is fun to walk through a winter woodlot and identify the leaf-holding species. In Tenhave Woods, in Royal Oak, you can see where the ridges run through the woods by looking at the location of the Beech trees. Hornbeams ring the low swamp forest. Winter often is the best time to get an overview of an area when you can see farther and having the ability to identify some species from a distance is helpful.

Copyright 2017 by Donald Drife

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Wolf’s Milk Slime Mold

Slime Molds are bizarre life forms that were classified as fungus but are now placed in their own kingdom. At one time, every living thing was placed in either the plant or animal kingdom. Currently, most scientists recognize six kingdoms: Plants, Animals, Protists (slime molds and algae), Fungi, Archaebacteria (bacteria found mainly in thermal vents), and Eubacteria; the remaining bacteria.

Wolf's Milk Slime Mold, (Lycogala epidendrum)

Wolf’s Milk Slime Mold, Cummingston Park, Royal Oak

Slime molds belong in the phylum Myxomycota. John Tyler Bonner writes, “[Myxomycetes are] no more than a bag of amoebae encased in a thin slime sheath, yet they manage to have various behaviors that are equal to those of animals who possess muscles and nerves with ganglia—that is, simple brains.”

The life cycle is complex. An over simplified description of the life cycle is that the spores develop into single cell organisms that then congregate into a fruiting mass producing spores. (If you desire a technical description of the life cycle see the UBC Botanical Garden Website)

Lycogala epidendrum, Wolf's Milk Slime Mold

Lycogala epidendrum, Wolf’s Milk Slime Mold

Wolf’s Milk Slime Mold (Lycogala epidendrum) is also called Toothpaste Slime Mold. It is circumpolar in the northern hemisphere, ranging throughout Michigan. The fruiting bodies congregate on logs (epidendrum means growing on logs), normally in the fall in Michigan. This is a slow moving slime mold taking days to change shape.

The small size of this slime mold makes it easy to overlook but its bright orange color draws your eye. It is easy to mistake this slime mold for a developing fungus of some kind. After a few days this bright orange color becomes chocolate brown and the slime mold disperses spores. Get out and look for it before the days get too cold.

Lycogala epidendrum Wolf's Milk Slime Mold

Wolf’s Milk Slime Mold

Witch-hazel Michigan’s late-bloomer

Hamamelis virginiana, Michigan

Witch-hazel flowers

Witch-hazel (Hamamelis virginiana) is a large shrub or small tree that blooms in the fall in Michigan. It grows in the Lower Peninsula and the western half of the Upper Peninsula. Outside of Michigan, it grows throughout the eastern United States reaching its western limit in Texas and Oklahoma. It is the last of our native woody plants to blossom. The flowers appear in most years after the plant has dropped its leaves. The yellow flowers with their four wiry petals form a pretty sight in the fall woods.

Hamamelis virginiana, Witch-hazel, Michigan

Witch-hazel, Oakland Co., Michigan

Hamamelis virginiana, seedpod,

Witch-hazel, Tenhave Woods, Oakland Co., Michigan.

The seeds ripen about the same time as the plant flowers. The seedpods shoot the seeds ten to fifteen feet. When I was a boy in Middle School, I had a Witch-Hazel branch with seedpods in my bedroom. (Doesn’t every boy go through this stage?) During the night, I heard a strange “Ping.” The seedpods were drying out and shooting their hard BB-sized seeds against my bedroom mirror.

Spiny Witch-hazel Gall

Spiny Witch-hazel Gall

This plant also produces Spiny Witch-hazel Galls. An aphid crawls into a leaf bud and secretes an enzyme. The irritation causes the plant to produce the gall around the aphid. The aphid reproduces within the gall and the gall provides a food source for the young. The life-cycle is more complex than this involving a secondary plant species host and some broods that are solely females. I cut open a gall from my garden, expecting it to be solid, but instead I discovered it was hollow. Several female aphids (the ones with wings) and at least one male were inside.

I love to see these flowers on their bare branches as I walk though the fall woods. Get out into a rich woods and see if you can find these last flowers of the year.

Spiny Witch-hazel Gall

Spiny Witch-hazel Gall with Aphids