Cottonwood Trees: The Fan Club

As I was thinking about the cottonwood trees in Eliza Howell Park recently, I recalled the old song, “Don’t Fence me In,” sung by “cowboys” like Gene Autry and Roy Rogers. It includes these lyrics:

     “Let me be by myself in the evenin’ breeze; Listen to the murmur of the cottonwood trees”

I don’t know if the cottonwood leaves actually murmur, but they definitely get my attention at this time of the year.

There are dozens of large Eastern Cottonwoods in the park, many of them quite close to the park road. One that stands alone next to the road is a favorite.

The Baltimore Orioles that spend three months of the year in the park are also fans of the cottonwoods. Of the 44 Baltimore Oriole nests that I have found in the park in the last 8 years, 24 have been in cottonwoods. The others have been scattered among 5 other tree species, with no other species having more than 7.

In 2019 the preference for cottonwoods is even more evident: 8 nests found; 7 in cottonwoods.

Photo by Kevin Murphy

Cottonwoods are dioecious, separate female and male trees. This is the first year I have made note of the sex of the cottonwoods selected by the Baltimore Orioles for nests. 5 of the 7 are female trees. Without additional records, of course, I don’t know if this is typical.

The sex difference is easiest to notice in the spring, when the male trees have reddish flowers (catkins), which appear earlier than female catkins.

The catkins on the female trees are green and the seed capsules are, at the beginning of June, getting ready to split open to release the seeds attached to the “cotton.” The cotton will soon be flying.

The orioles are fans of the hanging branches in which to build and hide their hanging nests. I have become a cottonwood fan partly because of the orioles, but I also simply admire the trees:

– the shaking leaves with the sky as background

– standing tall and leafless in January.

I am proud to be a member of the Eliza Howell Cottonwoods fan club.

 

The Female in Winter: Staghorn Sumac

There are not many seeds or fruits still hanging on in January and February on the trees and shrubs in Eliza Howell Park. They can, however, still be found on staghorn sumac in deep winter.

When I see “her” during my winter walks in the park, I am aware that “he” does not have anything much to show at this time of the year. Staghorn sumac is one of the few plant species that develop female and male flowers on completely different plants (“dioecious”); some plants are male and some are female.

Perhaps the best known dioecious plant is cannabis, an annual. In the case of cannabis, male plants are usually discarded because pollination is unwelcome; the unpollinated flowers of the female pants are considered the best part of the plant for psychoactive effect (according to what I read).

In our Detroit neighborhood, a good example of a dioecious tree is ginkgo, which has been planted as a shade tree along certain streets. In planting ginkgos, the females are not usually as welcome as the males because the female’s abundant fruit falls on sidewalks and produces an unpleasant smell when stepped on.

About the beginning of June in Eliza Howell, the sumac flowers develop on separate shrubs, the female on the left in the photo and the male on the right.

Though they were put together here for easier comparison, I do not usually find the female and male plants in close proximity. Staghorn sumac can grow from seed, of course, but it typically spreads by underground shoots (rhizomes). As a result, a clump of sumac is usually made up of plants all of the same sex; it is not really a clump, in fact, but parts of the same plant.

The quite large clump/plant along the nature trail that I observe most frequently is female, some meters away from the nearest male that I am aware of. Sumac depends upon insects, like bees, for pollination over such distances.

The male flowers do not last long. By late June, they are beginning to fade while the females (again on the left in the photo) are just beginning to turn the red that will persevere for many months.

For the next 6 months, the flowers and seed clusters stand out.

This picture is from the middle of July.

While birds eat the seeds, they seem to do so very late in the winter, after most of the other fruit in the park is gone. This picture was taken in the middle of December.

In many bird species, though not all, males are more colorful and attention-getting than females.

In the case of staghorn sumac, however, my attention is fully on the female for most of the year and only very briefly do I follow the male. She is there, standing proud, in the coldest part of winter.