Occasionally I’ll run across something on the web that I’d like to pass on, whether it be an important issue, or just a fun fact. In this case, it’s just a fun fact I found from the U of M Yard and Garden News. There are some deciduous trees that hold their leaves in the winter and don’t drop them until the next spring.Two of my favorites are the Northern pin oak and the Blue beech. I’ve always wondered if there was a word for that keeping-their-leaves-over-the-winter-thing and yes, there is. Read on.

By the way, I recommend that you plant the Northern pin oak and not the Eastern pin oak. Pin oaks (and all oaks in the Red oak genus) are very sensitive to low iron levels in the soil (which shows up as a yellowing of the leaves, a condition known as iron chlorosis) , but the northern pin oak has proved to be more tolerant. In either case always plant a pin oak in a slightly acid soil with good drainage.

What’s Up With That?! Weird Stuff and Fun Facts from the Gardening World
By Nancy Rose

Deciduous trees are supposed to drop their leaves in autumn, right? So why are there still lots of brown leaves clinging tenaciously to certain trees in our neighborhoods and natural areas? In a word: marcescence.

Deciduous trees that hold onto their leaves through the winter are described as marcescent (mahr-CESS-ent). Some tree species are more likely to show marcescense than others. In this region, oak species (Quercus) including pin oak, red oak, and white oak are the most noticeably marcescent trees. American hornbeam, also known as blue beech (Carpinus caroliniana), and ironwood, aka American hophornbeam (Ostrya virginiana) also tend to hold leaves. Other trees such as sugar maple are occasionally marcescent.

In autumn, the leaves of most deciduous trees develop an abscission layer where the petiole (leaf stalk) meets the branch. This allows the leaves to fall off without leaving an open wound on the stem. Dry leaves stay on marcescent trees because the leaves didn’t develop the normal abscission layer in autumn.

Marcescence is often a juvenile trait and may disappear as the tree matures. It also may not affect the entire tree; sometimes leaves persist only on scattered branches. Marcescence is typically based on a tree’s genetics, but sometimes weather plays a part. In years with early freezes tree leaves may be killed before developing an abscission layer, resulting in persistent brown leaves on many trees that aren’t usually marcescent. –Nancy Rose

Thanks, Nancy!