When Leaves Don’t Leave

by Nancy Rose

February 19, 2016

shingle oak leaves in winter

When Leaves Don’t Leave

American beech leaves in winter

The pale tan leaves of American beech (Fagus grandifolia) often persist all winter on young trees.
Photo by Nancy Rose

Deciduous trees typically lose all of their leaves by late autumn. But a stroll through the Arboretum reveals a scattering of deciduous trees and shrubs that still have leaves (albeit dry and brown) clinging tightly to branches. These plants are exhibiting marcescence, the trait of retaining plant parts after they are dead and dry. Marcescence most often refers to persistent leaves but can also refer to other parts such as flower corollas.

daimyo oak leaves in winter

Marcescent leaves are fairly common on oaks (Quercus), including this daimyo oak (Q. dentata 1590-52-C) on Bussey Hill.
Photo by Nancy Rose

Leaf marcescence is most often seen on juvenile plants and may disappear as the tree matures. It also may not affect the entire tree; sometimes leaves persist only on scattered branches. Unlike a typical deciduous leaf, a marcescent leaf doesn’t develop an abscission zone, an area at the base of the petiole containing a separation layer (thin-walled cells that break readily, allowing leaf drop) and, on the twig side, a protective layer of corky cells. The evolutionary reasons for marcescence are not clear, though theories include defense against herbivory (e.g., browsing by deer), protection of leaf buds from winter desiccation, and as a delayed source of nutrients or moisture-conserving mulch when the leaves finally fall and decompose in the spring.

Some woody plant species are more likely to exhibit marcescense than others. One of the most striking marcescent tree species is American beech (Fagus grandifolia), whose papery, pale tan winter leaves provide an easy identification feature as well as adding a ghostly shimmer in snow-filled woodlands. Many oak (Quercus) species are notably marcescent, and some hornbeams (Carpinus) and hophornbeams [pdf] (Ostrya) also tend to hold their leaves. Some witch-hazels [pdf] (Hamamelis) may retain foliage, which unfortunately can detract from the floral display of these winter-blooming shrubs. And if you visit the Arboretum this winter, note the handsomely marcescent specimens of narrow-leaved spicebush (Lindera angustifolia 740-75) along Bussey Road across from the lilac collection.

–Nancy Rose

13 thoughts on “When Leaves Don’t Leave

  1. Cool thanks for sharing I never gave it much thought but I’m sure someday one of my students will ask why there are still some leaves and now I have an answer.

  2. Excellent post, thanks Nancy. My wife and I were just wondering why the American Beech retain their leaves on a recent walk through the woods.

  3. The Japanese Maple I have in my yard is over 40 years old and this year is the first time that I recall it holding onto its leaves this late into the season. They typically drop in late October after going from their normal purple-ish green to a flaming bright red, then curling up and turning a reddish brown just before they drop. This year however, they are still attached and I was wondering if the tree is OK or if there may be some other reason for this….. Any advice? Thanks.

  4. Hello Jos-
    The unusual leaf retention this autumn on Japanese maples and some other normally non-marcescent deciduous trees can be explained by an unusual combination of weather events. October was abnormally warm, which delayed the process of leaf senescence for some trees. The abscission layer — thin-walled cells that break and allow the leaf stalk to drop off — had not fully developed, and then extremely cold temperatures occurred abruptly in early November. The well-below-freezing conditions froze and killed cells, including those in the not yet developed abscission layer, resulting in the dead, dry leaves staying on branches. The leaves will likely fall off over the winter or when new growth starts in early spring.
    Nancy Rose

  5. I raise japanese maples, tridents, blood red. Typically the leaves leave in Fall. Always bright and vibrant. This year all of my japanese maples retained their leaves. Even the youngest that are put in the basement for the first few winters. Im hoping it is not a signal for a disease. Thoughts?

  6. Even with very high, blustery winds and lots of snow this week, our Japanese Maples are still holding on to their leaves. I was so concerned about losing the trees, never having seen anything like this for the years we have had these trees. After reading the answer by Nancy Rose, I feel much better about their survival. Thank you for this site.

  7. Nearly all the crape myrtles here in New Jersey retained the dead foliage, and most as of mid—February still have a portion still attached. I am just hoping that they were thoroughly acclimated to the cold we had in early January when temperatures near the coast came close to 0f and low single digits.

  8. Another thank you re: the info re: Japanese Maples this fall/winter. I too was concerned about our beloved 40+ year old tree. We still have most of the leaves attached despite too recent heavy snowfalls.

  9. I’m in Baltimore. I took some comfort here hearing the reasons the leaves didn’t fall last winter, but now a very small number of branches (less than 10%) have large (fully grown?) leaves while most branches still have last years dead leaves.

  10. I live in a zone2A and my 10 year old Linden has kept most of the leaves. .so now I have an answer to ‘why’

  11. The concepts of deciduous/evergreen and climate and season all seem to make perfect sense regarding if and when leaves fall.

    What I find curious is why my largest tree (I don’t know what it is but it’s 50 ft high with small leaves) loses its leaves every late fall and regains them in spring, like clockwork, yet this year (it is late December) it is just as green and leafy as it was in July. It makes little sense.

    I am in Arizona where the lows are 40s and the highs are 60s at this time of year. The fall/winter has been normal, possibly a bit cooler than normal. Everything else is the same, other than this lovely tree.

    Can anyone explain why I am seeing such different behavior? For 20 years, this tree always lost its leaves. This year, no loss whatsoever.

  12. Hi Tom, thanks for your question. In Boston, marcescent leaves are more common when a hard freeze comes after an extended fall. The warm weather encourages a late flush of leaves that don’t have time to develop the abscission layers that allow them to separate. In those years, species that normally drop all of their leaves–including certain Asian maple species–may be spotted with an unexpected cover of coppery leaves in the winter. It sounds like your plant is responding to anomalous weather cues as well, but to get more detail about which specific variables are at play, I recommend reaching out to the Arizona Cooperative Extension.

  13. A beautiful American beech, over 100 years old, and the Copper beech, also very old, have still retained their leaves from last year. I keep looking for new foliage, but not yet. I pray they are still healthy.

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