American Chestnut is a large deciduous tree, not native to Minnesota, that before being decimated by Chestnut Blight, was a well formed tree with a towering crown often reaching 100 feet. The tree shown here is being grown as a landscape specimen and shows some deformity. In their native habitat it is mostly shrubby re-sprouts from the old stumps that are found. Work is being done on creating a blight resistant tree - see notes a page bottom.
The bark is smooth and grayish-brown when the tree is young with the trunk developing flat-ridged fissures as it ages.
Twigs are chestnut to orange brown in color, with lighter lenticels, without hair. Buds are the same color with 2 unequal outer scales that cover several smaller inner scales. Terminal buds are absent, instead lateral buds rise from a leaf scar.
Leaves are alternate on the twig, not lobed, but with margins sharply serrate, each tooth triangular, tapering to an awn that is usually more than 2 mm long. The shape is narrowly obovate, with a wedge shaped base, and tapering to a long narrow pointed tip. The upper surface is smooth but the underside has evenly distributed very small embedded glands.
Flowers: The tree is monoecious, that is with separate male and female flowers. Male flowers occur in slender yellow-green 6 to 8 inch hanging catkins from the leaf axils of last year's growth. The male flower usually has 12 stamens surrounding a pistillode (sterile pistil) that has whitish or yellowish hairs. Female flowers are found near the base of the catkins. They occur in sets of 3 in a cup shaped structure called a cupule. Though small, the sepals are distinct and there are 6 carpels and styles.
Seed: The cupule with its 3 flowers after fertilization develops into a 4-valved spiny structure that completely encloses 3 nuts. At maturity the cupule separates along the valve margins. The spines on the cupule are without hair. The nuts obovate in shape and flattened on one or two sides, about 3/4 inch to 1 inch in size. They are sweet and edible.
Habitat: American Chestnut grows in a mixed deciduous forest environment where there is good moisture, well drained soils; full sun is required for a good shape.
Names: The genus name, Castanea, is from the Greek word kastanaion and refers to a similar tree of Southern Europe. The species, dentata, refers to the prominent leaf teeth. The author names for the plant classification are: First to classify was ‘(Marshall)’ which refers to Humphry Marshall (1722-1801), American Botanist, who published in 1785 - Arboreteum Americanum: The American Grove, an Alphabetical Catalogue of Forest Trees and Shrubs, Natives of the American United States. His work was supplemented by "Borkh" which refers to Moritz Balthasar Borkhausen (1760 - 1806). German naturalist and forester. He published several works on forestry and woody plants and was the taxonomic author of the Alliaceae and Asclepiadaceae families.
Other species: The genus Castanea has three species. C. dentata is the most widespread in range while the other two are restricted to only part of that range and their cupules have only 2 valves not 4. C. ozarkensis has long spines on the fruiting cupule, often over 10 mm and the tree bark can be deeply fissured. C. pumila has cupules where the longest spines are usually less than 10mm and the tree bark is usually not fissured, or only shallowly.
Above: An American Chestnut growing in the Minnesota Landscape Arboretum, grown from seed and planted in 1971. Drawing from Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols.
Below: Leaves taper on each end with coarse teeth on the margins. Each triangular tooth ends in an awn.
Below: 1st photo - the underside of the leaf has minute glands embedded in the surface. 2nd photo - the staminate flowers are contained in a long catkin. Each flower has 12 stamens, visible in the photo.
BELOW: 1st photo - The developing spiny cupule that contained the female flowers at the base of the male catkin. 2nd photo - A mature cupule after in split open.
Below: 1st photo - Newer twig wood shows light colored lenticels. Buds are offset from previous leaf scars. 2nd photo - bark on a large branch beginning to show fissuring. 3rd photo - the trunk of this 50 year old tree showing good deep fissuring.
Notes: American Chestnut was once found in all areas east of the Mississippi River except Minnesota and Arkansas. Chestnut blight, caused by the fungus Cryphonectria parasitica has decimated the population and there may be only a few isolated spots where the blight has not penetrated. There are a number of breeding programs attempting to cross the species with a resistant Asian species but so far results are not encouraging.
Wood & its Uses: American Chestnut has had a number of uses, including construction and furniture.
Here is what Francois Michaux wrote in North American Silva (Ref. #26d): "The wood is strong, elastic, and capable of enduring the succession of dryness and moisture….especially valuable for posts. For shingles this wood is superior to any species of Oak, though it has the same defect of warping. it is not used extensively for staves, and its pores, like those of the Red Oak, are so open that it is proper only for dry wares. The Chestnut is little esteemed for fuel, and is not used in the cities of the United States, like the kindred species in Europe it is filled with air and snaps as it burns. The coal is excellent, and on some of the mountains of Pennsylvania where the Chestnut abounds, the woods in the neighborhood of the forges have been transformed into copes, which are cut every sixteen years for the furnaces."
Francois Michaux's father was Andre Michaux - (1746-1802), French botanist who made many exploring expeditions in the U.S. collecting and cataloging many species. Two important works of his are the Histoire des chênes de l'Amérique septentrionale (1801 - Oaks of North America), and the Flora Boreali-Americana (2 vols., 1803). His son Francois, traveled with him and the father’s notes were later used for the 3-volume North American Sylva, for which Thomas Nuttall provided some supplements.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"