How easily they spread can be seen in Mustila’s Alppiruusulaakso (Rhododendron Valley), where this shade-loving forest perennial has gradually developed into a troublesome weed. Unlike rosebay willow-herb, rattlesnake root thrives in shade so long as the soil is rich. Cutting immediately after flowering is one of the routine jobs aimed at preventing further spread of the seeds. However, rattlesnake root also spreads underground. Weeding simply encourages the roots to spread faster, so the only way to remove it from unwanted sites is by using weed-killer.