Saturday, September 3, 2016


I came across this little  tan leaved branch on a trail near Ponkapoag Pond, Blue Hill Reservation.  The dead, dried leaves mark it as an American chestnut (Castanea dentata).  If you walk these trails you will meet them often; always small, they are remnants of the great chestnuts of old. 

Until a century ago, American Chestnut was a major--sometimes dominant--tree of eastern forests, reaching three feet in diameter and a hundred feet in height.  In about 1904 a new fungal disease--probably imported on Asiatic chestnut trees--appeared on American chestnuts in the New York Zoological Park, infecting and killing trees and spreading like wildfire.  Today the tree is all but extinct in its natural range, existing only as stump sprouts that the fungus kills back regularly.

The tree I saw may have died of the severe drought; it is too small to be targeted by the fungus--certainly something killed it in mid-season.  The little thing had sprouted from the base of a somewhat-larger tree (upright near center), likely killed three or four years ago by chestnut blight.

When chestnut trunks reach two or three inches in diameter the fungus enters through cracks in the bark.  The fungus girdles the trunk before creating the orange sporangia on the bark that spread the spores that reproduce it.  The trunk dies but the roots often survive to send up another sprout, however these sprouts almost never become mature enough to flower and set seed.  In a cruel irony, by hanging on these trees maintain the fungus population.  But even if the chestnuts died for good, red oak is able to host the fungus without suffering serious harm; we will likely never be rid of it. 

So these "ghost trees" have existed for a century in a sort of limbo, not completely dead nor entirely alive.  The rotted stump at the base (below) must have been dead about a century: it could not have reached that diameter after the fungus arrived in the area.  Now, after a hundred years of stubbornness, this tree might finally be dead.*  

Efforts to breed resistant trees have been underway for decades; perhaps newer recombinant DNA technology will finally bring the tree back.

  Chestnut blight fungus (Cryphonectria parasitica aka Endothia parasitica) has almost entirely wiped out mature chestnuts from their natural range.  Only stump sprouts remain.

*Or have I just noticed in the photo a new sprout with a couple of long, dark green, saw-toothed chestnut leaves between stump and shoots?


  1. When I was a kid - ,I remember playing with what we called 'horse chestnuts.' Firstvyiu had to get off the prickly green shell to get to the glossy nut. I am guessing these were a different species.

  2. Yup. The two genera(Castanea and Aesculus) are not closely related. When we were kids, we'd extract those beautiful horsechestnuts. put 'em on shoelaces, and whack each other's to see whose would survive, winning the contest. Today I have no idea why!