Botany Blog Plants of the Northeastern U.S.

This image is of a Compass Plant (Silphium laciniatum) growing in a prairie restoration in northeastern IL.

One of my favorite books is the Sand County Almanac by Aldo Leopold. It was required reading for a course that I took at community college. This was one of those rare times when, rather than finding it a chore to read an assigned text, I thoroughly enjoyed the book and even read the chapters that were not required for the course. I have read it again several times since. At the time I did not know many of the plants described in Leopold’s essays, but I found the descriptions colorful non-the-less. Having since lived in the Midwest and studied botany there for many years, I can now appreciate the book even more. I would like to share here an excerpt from that book about Silphiums, which are robust, deep-rooted perennials often found in prairies and easy to grow in a sunny garden. Leopold wrote:

“Heretofore unreachable by sythe or mower, this yard-square relic of original Wisconsin gives birth, each July, to a man-high stalk of compass plant or cutleaf Silphium, spangled with saucer-sized yellow blooms resembling sunflowers. It is the sole remnant of this plant along this highway, and perhaps the sole remnant in the western half of our county. What a thousand acres of Silphiums looked like when they tickled the bellies of the buffalo is a question never again to be answered, and perhaps not even asked.

This year I found the Silphium in first bloom on 24 July, a week later than usual; during the last six years the average date was 15 July. When I passed the graveyard again on 3 August, the fence had been removed by a road crew, and the Silphium cut. It is easy now to predict the future; for a few years my Silphium will try in vain to rise above the mowing machine, and then it will die. With it will die the prairie epoch.

The Highway Department says that 100,000 cars pass yearly over this route during the three summer months when the Silphium is in bloom. In them must ride at least 100,000 people who have ‘taken’ what is called history, and perhaps 25,000 who have ‘taken’ what is called botany. Yet I doubt whether a dozen have seen the Silphium, and of these hardly one will notice its demise. If I were to tell a preacher of the adjoining church that the road crew has been burning history books in his cemetery, under the guise of mowing weeds, he would be amazed and uncomprehending. How could a weed be a book?

This is one little episode in the funeral of the native flora, which in turn is one episode in the funeral of the floras of the world. Mechanized man, oblivious of floras, is proud of his progress in cleaning up the landscape on which, willy-nilly, he must live out his days. It might be wise to prohibit at once all teaching of real botany and real history, lest some future citizen suffer qualms about the floristic price of his good life.”

While these plants are easy to grow, they have very deep taproots making them nearly impossible to transplant. The best way to grow them is by directly sowing the seeds. It usually takes two or three years for them to reach sufficient size to bloom, and several more to reach their full potential. Besides Compass Plant, other species include Prairie Dock (Silphium terebinthinaceum), Rosin Weed (Silphium integrifolium), and Cup Plant (Silphium perfoliatum).

It is fall now and the leaves are just beginning to change. On a recent visit to a local research station I snapped this picture of a softball-sized, spiny fruit of what was likely a hybrid between Chinese Chestnut (Castanea mollissima) and American Chestnut (Castanea dentata). I think it was a hybrid as the leaves did not appear downy underneath (as is typical of Chinese Chestnut) but the spines of the fruit are rather thick (they would be thinner in American Chestnut). If one could go back in time, a little over 100 years ago one would find the forests of the northeast were dominated by the American Chestnut. The smooth, brown seeds found inside these spiny capsules were an important winter food source for early settlers and also for wildlife. Today it is rare to find one of these trees and even rarer to find one that bares fruit.

It took only 50 years following the introduction of Chestnut Blight (Cryphonectria parasitica) to decimate the American Chestnut throughout its range. Virtually all trees were killed back to the ground and only a few survivors exists today as “living stumps”. Occasionally a tree may be found that has obtained sufficient size in order to produce fruit. Trees have been planted outside the native range and are important sources of seed for ongoing research to develop resistance to the disease.

There are two main techniques that researchers are currently using to develop blight-resistant American Chestnut. One is the development of hybrids with Chinese Chestnut, which ironically was the host which carried the blight to North America in the first place. Hybrids are then back-crossed with American Chestnut in an effort to reduce the percentage of Chinese Chestnut traits while maintaining blight resistance. The other technique being utilized is genetic engineering; researchers attempt to add specific genes to provide blight resistance to pure American Chestnut.