Species of the Week: Leatherflower

Species of the Week
Number 5 -- July 3, 2006

This is the fifth species featured in the Species of the Week feature of the Wildwood Web. To see the earlier featured species check the Species of the Week archives.

Leatherflower

Clematis viorna

If you are used to the showy, spreading petals (actually sepals) of the various kinds of cultivated clematis, you will be surprised to find that leatherflower is a member of that genus. So different from the others, is Clematis viorna, and other similar species also called leatherflowers, that they are placed in a special section of the genus, and have been placed in their own genus in the past, the genus Viorna.

Leatherflowers are in the Ranunculaceae, the Buttercup Family, like Species of the Week number 4, Thimbleweed. Leatherflowers, like thimbleweeds and most members of the Buttercup Family, have no petals. Instead the sepals are modified to look like petals. In leatherflowers, the four sepals are tough and leathery, hence the common name, and are a subdued red-purple shade. The sepals are fused towards the base, and curl back at the tips, forming a very elegant urn-shaped flower. The leaves are compound, being composed of three, five or seven leaflets. Only two leaflets are seen in the picture at left, but three can be made out in the picture below. The plant is a vine, and climbs over other plants.

Once fertilized, the flowers develop into fruits, which are also very interesting, as seen in the picture below. The fruit is called an achene by botanists. This is defined as a dry, one-seeded fruit, with the outer wall tightly enclosing the seed. In leatherflowers, and in other clematis species, the achene has a long, hairy tail attached. Many achenes cluster together, with the tails sticking out in a loose spiral. these clusters are very dramatic and quite decorative.

Clematis viorna is found in moist woods and thickets from Pennsylvania to Illinois and Missouri, south to Georgia and Mississippi. In Wildwood it is abundant along Wildwood Drive, perhaps favoring the seeps that occur in the banks under the power lines. The genus Clematis is found worldwide throughout the temperate and subtropical regions. The name Clematis is Greek and refers to some climbing plant, though no one is sure exactly which.

Southwest Virginia is an interesting area for leatherflowers. Besides the common Clematis viorna, look for Addison's leatherflower, Clematis addisonii. This rare species is found only in Botetourt, Montgomery, Roanoke, and Rockbridge counties in Virginia. It likes calcareous dry woods, glades and outcrops. According to the Digital Atlas of the Virginia Flora maintained by the Massey Herbarium at Virginia Tech, it is found only on sites underlain by a particular geological formation, the Elbrook Formation, composed mostly of dolomite, but also containing limestone, shale and siltstone. Perhaps this species has evolved to thrive in soils having a peculiar mineral chemistry found only in the Elbrook Formation. Addison's leatherflower differs from the common species in having many leaves, sometimes all of them, simple, that is, not compound. The leaves that are compound generally lack the last leaflet, but have a tendril instead, like pea plants do. When the leaves are compound, the lowest pair are much larger than the next pair up, unlike in the common species where the sizes are more equal. In addition to this species, two other leatherflowers, C. albicoma and C. viticaulis, are found further north of us, in shale barrens of western Virginia and adjacent West Virginia. Apparently something about the geology of western Virginia favors diversity in leatherflowers!

The common leatherflower will be gracing Wildwood Park for much of the early summer. While not brilliantly colorful, the flowers are shapely and elegant. Still later in the summer, the striking fruit clusters can be seen. Outside of Wildwood, keep an eye out for its rare cousins.

GGC