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A lesser known but important purpose of the National Arboretum is to collect and preserve ornamental plant germplasm.
Germ what? That’s a fancy way of saying we find and grow plants that have important or unique genetic traits that are
beneficial to the ornamental nursery industry, much the same way libraries maintain reference collections of important
or historical books. Sometimes, the National Arboretum is one of just a few botanical collections in the world that is
growing a particular woody or herbaceous plant species.
Mexican flowering dogwood (Cornus florida subsp. urbiniana) is one such unique plant. Originally from eastern Mexico,
this dogwood is a subspecies of our native common flowering dogwood (Cornus florida). It is quite rare in the United States,
found in only a few botanical gardens and arboreta, including the National Arboretum (two specimens are located in the
Dogwood Collection).
Mexican flowering dogwood generates a lot of interest from those lucky enough to see it in flower. Its unusual
flowers are quite different from those on the common eastern dogwood. The white, petal-like bracts are narrow,
creased, and joined at the top, which prevents the flowers from opening completely, making small "Chinese lanterns"
at the branch tips. Hardy to USDA Zones 6 – 7, this dogwood
also holds its foliage much longer than the average native dogwood, prolonging its fall color display. In our collection,
it has shown signs of resistance to leaf diseases that commonly affect other forms of eastern dogwood. Structurally, its
form is somewhat taller and narrower than the eastern dogwood’s; the older of the two trees in our
Dogwood Collection, which was acquired in 1992,
is approximately 22 feet tall and 16 feet wide.
Given the Mexican flowering dogwood’s distinctive qualities, it is being considered for a spot along the arboretum’s new
Flowering Tree Walk. Currently, Mexican flowering dogwood is offered in the nursery trade by only a few, mostly mail order
nurseries. Hopefully that will change in the future as more people see this tree’s wonderful floral display and create a demand
for it in the marketplace.
For additional information, see the article written by National Arboretum scientists:
Cornus florida subsp. urbiniana (Rose) Rickett from Mexico: the correct name for "C. florida var. pringlei"
by, Dr. Theodore R. Dudley and Frank S. Santamour, Jr in Phytologia 73(3):169-179 (1992).
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