Kansas Wildflowers and Grasses - Black swallow wort

BLACK SWALLOW WORT

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Cynanchum louiseae Kartesz & Gandhi

[=Cynanchum nigrum (L. ) Pers.]

[=Vincetoxicum nigrum (L. ) Moench]

Geary County, Kansas

Perennial

Height: Climbing vine

Family: Asclepiadaceae - Milkweed Family

Flowering Period: May, June, July, August, September

Also Called:

Dog-strangling vine.

Stems:

Few to several, simple or branched, mostly slender, 3 to 6 feet long, soft-hairy in longitudinal lines.

Leaves:

Opposite, widely spreading, narrowly to broadly ovate, 1.2 to 4 inches long, .6 to 2.8 inches wide, short-hairy along veins and margins; tips long-tapering to points; bases rounded to shallowly heart-shaped; stalks 1/10 to 3/5 inch long.

Inflorescences:

Cymes, umbel-like, in leaf axils, 5- to 14-flowered; stalks 1/5 to 3/5 inch long.

Flowers:

1/4 to 1/3 inch across; stalks slender, to 1/4 inch long, short-hairy; calyx lobes 5, narrowly triangular to ovate, green to purplish, sparsely short-hairy; corolla erect or ascending, lobes 5, triangular, dark purple to nearly black, fleshy, inner surface minutely hairy, outer surface glabrous; corona cup-like disc, fleshy, shallowly lobed, dark purple to nearly black.

Fruits:

Pods, single or paired, narrowly spindle-shaped, 1.6 to 2.8 inches long, smooth; seeds many, flattened, ovate, to 1/3 inch long, brown, tufted with long, silky white hairs.

Habitat:

Open disturbed areas, woods, thickets, fence rows, roadsides; moist, sunny places.

Distribution:

East 1/3 of Kansas.

Origin:

Introduced - native of Southern Europe. Occasionally escaped from cultivation.

Comments:

An invasive species that should be eradicated when encountered.

Black swallow wort flowers