Chestnut Planting Reaches Critical Stage

Jeanne Siviski

     In just five years, the Maine Chapter of the American Chestnut Foundation (ME-TACF) predicts they will be producing potentially blight-resistant chestnut seed.   Reintroduction of the American chestnut to the Maine and eastern U.S. forest ecosystems is an enormous undertaking. In Maine, the northernmost limit of the American chestnut’s historical range, a big concern is cold-hardiness. Field testing will be needed to find the best methods for introduction.  The focus of field tests conducted by Prof. Brian Roth at the Ladd Forest, a Maine Woodland Owners land trust site in Vienna, will be trade-offs between cold hardiness and disease resistance.

     Roth is a ME-TACF board member and associate director of the Cooperative Forestry Research Unit at the University of Maine. He said he was enthused when Maine Woodland Owners Deputy Executive Director, Bill Williams, showed him the Ladd Forest site because it is on a hillside with well-drained Hollis soil that had recently been partially harvested.

    Seventy foot pine, and a smattering of beech, maple and oak, offer protective shelterwood that will hopefully moderate cold damage from low winter temperatures.  Forest canopies can have a thermal effect, with temperatures a fewer degrees warmer and lighter winds.

     The experimental planting, which is being replicated on land of the New England Forestry Foundation in Knox, contains sources from warm and cold temperature zones with all available combinations of cold tolerance and blight resistance.  The research area covers approximately one acre, with small replicated “blocks” of 36 trees within each source, planted as seed on eight foot spacing.  Individual planting spots are marked with small flags, colorcoded by block, forming a quilt of blue, lime green, yellow, orange, white and red on the hillside. Within each of these blocks, there are four to six sources of seeds from individual mother trees.  One of the seed sources is from China. “Chinese chestnuts will be our benchmark,” Roth said, in terms of blight resistance. Having co-evolved with the disease over thousands of years, Chinese chestnuts have good resistance.

      Chestnut seeds from northeastern and southestern parts of the United States are included in the mix. “We think the ones from the south will grow more rapidly and start earlier in the season,”  Roth said. However, since they are not adapted to cold Maine winters, Roth feels they may be susceptible to cold injury and shoot die-back. Southern sources of American chestnuts may tend to devote more energy to competing with other species in their environment, while more northern American chestnuts concentrate resources on protecting tissues from freezing.

     Kendra Gurney, New England regional science coordinator for TACF, said that Roth’s tests would provide data about “how we can spread things around before we have to worry about where they came from.” In terms of cold hardiness, they’re not as concerned with what happens year-to-year, as they are with extreme events, such as last February’s record cold.

     “In an experiment of this size and complexity,” Roth said, “there is always something we learn that we weren’t expecting.” But finding an ideal mix of cold hardiness and blight-resistance is Roth’s ultimate goal.  “It’s a needle in a haystack,” he said. “Somewhere out there is the right combination of genes adapted for Maine’s forests.”