It’s an unassuming flower, the pennyroyal, with its small, pointed, lavender petals cupped by deep green leaves. Pennyroyal flowers grow in kusudama-like clusters that thread a single, delicate stem. A cousin to mint, pennyroyal smells good (if a bit overwhelming) and can help keep fleas and mosquitoes at bay. Ingested as a tea or an oil, pennyroyal can hurry along an annoyingly late period. And in high enough doses, the story goes, pennyroyal can allow…