Seed germination of Viola pedata, a key larval host of a rare butterfly

Birdfoot violet (Viola pedata L. [Violaceae]) is one of several Viola species that act as larval host plants for the rare regal fritillary butterfly (Speyeria idalia Drury [Nymphalidae, Argynninae]). Restoration or expansion of existing populations of V. pedata populations can be an important tool for preventing local extinction of S. idalia. Knowledge of environmental cues that affect germination will contribute to restoration efforts. Our investigation of seed germination of V. pedata indicates stratification is necessary for germination. Seeds exposed to longer lengths of warm-dry conditions and stratification had significantly higher germination rates compared with seeds exposed for shorter time periods. Elaiosome removal had little effect on percent germination, but indirect evidence suggests that elaiosomes increased vulnerability to pathogen attack. We recommend future efforts to germinate V. pedata seeds should begin by removing elaiosomes and exposing seeds to warm-dry conditions for 8 to 12 wk and then stratifying them for 8 to 12 wk.