What is a swallow-wort? Here are some definitions.
Noun
Any of several species of plants the parts of which resemble a swallow's tail:
Vincetoxicum hirundinaria
Any of several vines of the genus Cynanchum, especially black swallow-wort (Vincetoxicum nigrum, also Cynanchum nigrum) or white swallowwort (Cynanchum vincetoxicum).