Perilla mint (Perilla frutescens Britt
) is an erect, herbaceous annual that is a member of the Lamiaceae or mint family. It's leaves are egg-shaped and can be purple or green tinged with purple. It produces many small clusters of white to purplish-white flowers.
Perilla mint is considered an invasive weed in the Mid-Atlantic United States. All parts of the plant are toxic, in fresh or dry form, however it is most toxic in fresh form when flowers and fruit are present. It has a distinctive, aromatic, minty odor when the stems and leaves are crushed. Look for perilla mint in spring and early summer. Perilla mint tends to grow in semi-shaded areas near woodland edges, fence rows, and near farm structures.
Horses usually will not eat perilla mint if other forage is available, unless it is accidentally baled into the hay. It becomes more dangerous to horses late in the summer and early fall. Horses that have consumed perilla mint might exhibit clinical signs of respiratory distress, such as labored breathing and possibly an elevated temperature. In cattle, consumption of perilla mint causes a respiratory distress syndrome known as panting disease.