Tales from the Forest: the American Chestnut

ConCradle educator Courtney Long found herself on a very well-loved trail in Pisgah National Forest. Although atypically warm for this late autumn afternoon, the colors remained mesmerizing. She was on the hunt for a very special find that a forest visitor discovered. She was seeking a tree that had once dominated forests of western North Carolina. A tree that once towered 100 feet above the forest floor and could reach widths of 10 feet: The American chestnut, or Castanea dentata. The sheer mass and abundance of these trees until mid-20th century had once allowed finding this species a breezy task. Now identification of these trees requires more attention. Catching her mind drifting into daydreams, Courtney reminded herself to keep a keen eye…

A quick history:

An estimated 4 billion chestnut trees once reigned eastern forests. For many species of wildlife chestnuts were a primary food source. Early settlers relied on the high quality wood, while the chestnuts were a source of income and livestock feed. Other parts of the tree were utilized for medicine and tanning. The American chestnut hosts many pests; including a root rot fungus, gall wasps, weevils, etc. (Note: the invasive Asian chestnut gall wasps were introduced in the 1970’s.) The rapid spread of the chestnut blight was most devastating, killing nearly the entire population. From the first discovery of the chestnut blight in 1904, some say 3.5 billion chestnuts were wiped out by the 1950’s. Today only small stands remain scattered, some with specimens as tall as 80-feet.

chestnuts-species-leaves

From L to R: American chestnut, Chinese hybrid, chestnut oak

Chestnuts today:

Although this Asian fungus kills the tree, it does not affect the root systems. Many American chestnuts found today are young and have sprouted from the root ball. The Cradle of Forestry Heritage Site has an example of this occurrence nearby the schoolhouse. Even though suckers from the root system survive, chestnuts take 7-8 years before maturing to bear fruit. Most suckers are infected with the blight before they reach this maturity. Hope persists for naturally resistant trees in the wild. 

This is why Courtney was tasked with seeking out an American chestnut sighting in Pisgah National Forest. The forest hiker noted a large specimen growing just off the trail and at his feet laid dozens of burs. “Surely people have noticed this. There are burs everwhere,” he insisted. “I wonder if it’s a chinquapin,” Courtney pondered as she recalled the phone conversation. Chinquapins are the cousins of chestnuts and bear similar, although smaller, burs and nuts. Courtney noted a couple of trailside chinquapins as she meandered higher in elevation. 

american-chesnut-leaves

Castanea dentata

Research efforts toward resistant trees:

The Backcross Method-Scientists use a series of backcrosses that maximize American genes and features while gaining resistance to the fungus. This process begins with a 100% American chestnut crossing with a 100% Chinese chestnut in order to obtain the blight resistant gene. These hybrids are continually crossed until a 15/16th American chestnut hybrid with resistance is grown. Seemingly healthy looking American chestnuts found in the wild are actually hybrids with the blight resistant Chinese chestnut. 

OXO Gene– A gene discovered in wheat encodes for an enzyme called oxalate oxidase (OxO). This enzyme is responsible for disease resistance in wheat and similar grasses. When transferred to the genes of American chestnuts, seedlings exhibit a resistance to the blight. 

A catkin, bur and nuts of an American chestnut

A catkin, bur and nuts of an American chestnut found in Pisgah National Forest, NC.

 “Ouch!” she yelped as she threw down the bur. Courtney had found several American chestnuts. Most looked unhealthy, either infected by the blight or powdery mildew on the leaves. Others had produced not just a handful of burs but possibly hundreds. Evidence of this nut as a wildlife favorite was found by the number of burs pried open and the nutrient rich prizes missing. Courtney had attempted to open one and resulted in a few needle pricks on her fingers.

Back in her office she prepped the samples and wrote down pertinent information the American Chestnut Foundation could use in positive identification. Shipped off to Asheville, she waited 5-6 weeks. 

How can you help?:

If you think you find a tree, follow the guidelines on the American Chestnut Foundation website and send in a leaf and twig sample. After testing, ACF informs you whether the tree found is a hybrid or 100%. This process can take a few weeks. If it is a fruit bearing tree, ACF may ask for you to collect chestnuts for them. These could aid in restoration research and efforts. This is a great impromptu activity with kids and teaches them ways they can be good stewards of their public lands.