Monthly Archives: September 2010

Resurrecting the American Chestnut Tree

american chestnutOnce upon a time, when most of the eastern US was covered with a thick canopy of trees, the dominant tree species was the American Chestnut (Castanea dentata). Loaded with sweet and nutritious nuts, chestnut was an important “mast” tree, feeding and sheltering many forms of wildlife. In the early 20th century, a fungal blight imported on Chinese chestnut trees tore its way through our native chestnuts, virtually obliterating the species from our landscape in just a few decades. Since then, oak and hickory have replaced chestnut as the dominant tree species in many areas of the northeast, but there is hope for the return of the American chestnut to our landscapes. Healthy American chestnuts are occasionally found still growing in various parts of the country, unaffected by the deadly blight, proof that with enough genetic diversity in a species, often a few individuals can withstand whatever nature throws at them.

This is where science, technology, horticulture and medicine have all come together to resurrect the magnificent American chestnut species. Through a lengthy process of controlled pollination, genes from the blight-resistant Chinese chestnut are crossed and back-crossed into the American chestnut gene pool, which over the span of many generations develops a greater resistance to the blight. Those offspring that show the most resistance are then cross-pollinated with pollen from blight-free American specimums. The healthiest of all are inoculated with the blight, and nuts from these chestnuts are being planted in various areas across the country for further selection for regional adapability.

How can you help this project? If you own woodlands, or just like to walk in the woods, you can contribute to the American chestnut restoration program by looking for mature, surviving American chestnuts to add to the pool of blight-resistant genetic material. If you see what you believe may be a healthy American chestnut, contact The American Tree Foundation for details of how to collect and send a leaf and twig sample for analysis. The resulting nuts will then be planted in chestnut orchards to continue the breeding and selection program. To date, over 500 “mother trees” have been found along the eastern seaboard, and regional groups are hoping to find more.

To identify an American chestnut , look closely at the leaves. They are unmistakeably long and toothed (see below), but look a lot like the foliage of other trees such as American beechchestnut oak, as well as Chinese, Japanese and European chestnut. One feature that sets them apart is that American chestnut leaves are not hairy, whereas other similar tree species have hairy leaves.

chestnut foliage

Even if you can’t find mature blight-free American chestnuts on your travels, you may well spot the living remains of blight-affected chestnut trees that collapsed many decades ago. Chestnuts affected with blight can take a long time to die, and living stems will continue to sprout from old root systems, growing to about 10-15′ high before being attacked by the blight. If you find a stem with living leaves alongside dead stems rising from the same root base (see above), you have found an old American chestnut dying from blight. You might even be lucky enough to find the remains of the long-fallen trunks. The lightweight but hard wood of chestnuts was highly prized by settlers for its rot-resistance, and fence posts, telephone poles, coffins, furniture and even pianos were some of the products that fueled a thriving chestnut logging industry over the centuries.

The good news for wildlife gardeners is that in time, we will be able to buy seedlings of American chestnuts to restore this majestic tree back into our landscapes. As Sudden Oak Death (another imported pathogen) threatens our native oaks, the re-introduction of the American chestnut could eventually fill gaps left by other declining trees, pre-empting the incursion of invasive species and insuring the health of our forests and woodlands into the future.

Photo credits:

Historical photo of American chestnut tree, W. Virginia, 1924, courtesy of the Forest History Society, Durham, N.C. 

Photo of blight-infected American chestnut at Broadmeadow Brook Audubon Sanctuary in Worcester, MA. by Ellen Sousa.