The no-rain weather continues in Caddo parish. And it's been hot the past few days, too. Around the arboretum, a couple trees are dropping leaves, several trees are turning colors, and a good many trees are dropping fruits, mostly acorns.
Our tree of the week is in a class of its own; its fruits are very interesting. This is 'Dunstan', a hybrid between the American chestnut (Castanea dentata) and the Chinese chestnut (Castanea mollissima). Until the 20th century, the American chestnut was a bedrock species in the uplands of Eastern America. A disease was introduced into the native tree populations, and subsequently the American chestnut went the way of the buffalo; minor populations survive but nothing like the past glory remains.
Ed Leuck acquired Dunstan from Sherwood Akin nursery in Sibley, Louisiana, and it was planted in January 1996, at the bottom of a hill near the stream. In 2005, it was damaged by a falling mockernut hickory (Carya tomentosa), which broke its top. Today it's in good health, growing in a shady spot near the Fitness Center.
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| Dunstan is pictured in the center. The on-site native sweet gum (Liquidambar styraciflua) is on the far left. Sweetbay magnolias (Magnolia virginiana) and a basswood (Tilia caroliniana) are in the background. This is a very shady spot. |
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| Behind Dunstan, on the opposite side of the stream, the arboretum's floodplain is located. A red maple (Acer rubrum) is pictured on the far left and an overcup oak (Quercus lyrata) is pictured on the far right of the photo. |
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| The narrow leaves pictured above are characteristic of Castanea dentata, rather than C. mollissima. |
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| In the leaf litter, we can find the fruits. They must be falling from way up top because none could be spotted on the lower branches. |
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| The husk of the fruit is extremely spiny, and it hurts! Thick gloves are recommended. |
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| The wider leaf pictured above resembles the leaves of Castanea mollissima. The delicately serrated leaf margins of Dunstan also resemble the leaves of C. mollissima, rather than the more coarsely toothed leaves of C. dentata. |
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| The underside of the leaf is fuzzy, a characteristic of C. mollissima. The husk of the fruit pictured above is split: get a pair of gloves and pull it apart. |
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| The large prickly husk concealed three small nuts. The interior of the husk is velvety. |
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| Light-grey furrowed bark of a 20-something-year-old tree |
Click here for more images of the arboretum's American chestnut hybrid.
For more information about the American and Chinese chestnuts and their Dunstan, please see the following links:
University of Marlyand Extension
Chestnut Hill Nursery and Orchards - creator of Dunstan
Virginia Tech Dendrology - Castanea dentata
Virginia Tech Dendrology - Castanea mollissima
