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There are a number of weeds that can be found in lawns, turf, and landscapes that may be coveted for their culinary uses. Wild herbs are often at the top of the list. For example, wild sage grows high up in the Rocky Mountains and adds a delicious taste and aroma to many culinary experiences. Wild strawberries and wild garlic are prevalent in many parts of the country, and although they are not usually desired growths in landscapes, they are edible and have many culinary uses. Perilla mint, however, is not an edible herb. In fact, when perilla mint is found in pastures, it endangers cattle and other livestock as it is highly toxic to ruminants.

Perilla mint belongs to the same family as cultivated mint. Its scientific name is Perilla frutescens and is easily identified by the aroma and appearance. Like cultivated mint, perilla mint has a strong minty aroma. Plants can grow as tall as four feet, and leaves are almost heart-shaped and toothed at the edges. The undersides of leaves may be purplish in color, and stems are square in shape and hairy. Flowers may occur in clusters, which can give a mature plant a bottle-brush appearance. Individual flowers are small and white to whitish purple in color and hairy, perilla mint is often referred to as beefsteak plant, common perilla, purple perilla, purple mint, and Chinese basil, just to name a few.

This variety of weedy mint originated in southeast Asia. It is often cultivated and considered an ornamental plant in gardens because of its purple and green foliage. However, it is an escaped ornamental, which is what caused its spread and become a weedy pest mostly in the southeastern United States. It can be found in pastures, edges of woods, along farm structures, and along fence rows.

Plants are spread through seeds, and roots are a shallow and fibrous taproot. They emerge between late April and early June. This is also the best time to scout for perilla mint in pastures, farm structures, and fence rows. By late summer, plants are often too large to remove mechanically or with an approved weed killer.

All parts of the perilla mint plant are toxic to cattle, livestock, sheep, and horses. When ingested by livestock, the leaves contain ketones that cause respiratory distress. It is one of the most toxic weeds in the southeastern United States for cattle and livestock and so checking pastures and grazing areas for the distinctive-looking weed are critical. In most cases, grazing animals are not prone to eat perilla mint plants. However, in late fall and early winter when cattle and livestock are hungry, and there isn’t enough grass or greenery to eat, they will often consume this toxic plant.

Even though it is highly toxic for livestock, there have been some human uses for perilla mint. Their seeds have been used to make cooking oil and fuel. Native Americans used to use parts of the plant medicinally, although it is not currently recommended.

Because it is the most toxic known plant to cattle and livestock, eliminating the plant is very important. The best time to scout areas for these weeds are in late spring and early summer. Mowing them down before they produce seeds will prevent the spread of perilla mint. If it is not managed before late summer, it is crucial to provide an adequate food source to grazing animals to avoid them from consuming them. Once they begin flowering in late summer, they are considerably more deadly to farm animals. Broadleaf herbicides specific to pastures are also a reasonably effective means of controlling perilla mint.