Mem. Torrey Bot. Club 2: 28. 1890.
Stems usually ascending to erect, occasionally somewhat viny, 0.6-1 m, glabrous. Leaves all simple, blade often 1-pinnate on distal and middle leaves on vigorous plants 4-13 × 2-9.5 cm; leaflets 2-6 plus additional tendril-like terminal leaflet, ovate, unlobed, 1.5-6 × 1-4.5 cm, not prominently reticulate; surfaces abaxially glabrous and glaucous. Inflorescences terminal and axillary, flowers solitary. Flowers ovoid to broadly urn-shaped; sepals purple or reddish purple, whitish toward tips, ovatelanceolate, 1.2-2.5 cm, margins not expanded, thick, not crispate, tomentose, tips acute, spreading, abaxially glabrous. Achenes: bodies puberulent; beak 2.5-3.5 cm, plumose. 2n = 16.
Phenology: Flowering spring–early summer.
Habitat: Calcareous, dry woods, glades, rock outcrops
Elevation: 200-600 m
Of conservation concern.
Clematis addisonii is known only from Botetourt, Montgomery, Roanoke, and Rockbridge counties in western Virginia. Reports of this infrequent species from other southeastern states have been based on misidentified specimens (W. M. Dennis 1976).
"thick" is not a number.