Noun
Any of several species of plants whose parts resemble a swallow's tail:
Any of several vines of genus Vincetoxicum (syn. Cynanchum), especially black swallow-wort (Vincetoxicum nigrum, syn. Cynanchum nigrum) or white swallowwort (Vincetoxicum hirundinaria, syn. Cynanchum vincetoxicum)
The greater celandine / tetterwort, Chelidonium majus or Sanguinaria canadensis.
Any of various plants of the genus Asclepias.
The plant Euphorbia maculata (spotted spurge).
Seutera angustifolia
Calotropis gen. et spp.
Source: en.wiktionary.orgswallow wort