Rue, Ruta graveolens, is an almost perfect nectar and host plant for the butterfly garden. It’s pretty, attracts butterflies with its yellow flowers and is a host plant for black swallowtails and occasionally giant swallowtail butterflies. It also will usually come back every year and reseeds freely.
It only has one flaw – it can cause a rash. I’ve never gotten the rash, but because of that potential problem I don’t recommend it for schools. I almost always wear gloves so that may have protected me somewhat. It even got a mention on an old Doc Martin episode, so the problem is real.