Beefsteak plant (Perilla frutescens)

Synonyms: Ocimum frutescens, Perilla ocymoides, Perilla urticifolia

Common Names: Perilla mint, perilla, shiso, purple mint, Chinese basil

Description:

Beefsteak plant (Perilla frutescens) is an aromatic annual in the mint family, native to East and Southeast Asia, where it is grown as the herb shiso [1][2]. Brought to North America as a culinary and ornamental plant, it escapes into pastures, woods, and disturbed ground, where it reseeds heavily and forms large patches that crowd out native plants [2]. MISIN tracks it because it spreads quickly by seed and ? importantly ? is poisonous to cattle and other grazing animals [2][3].

Habit:

Beefsteak plant is an upright annual, usually 1.5 to 3 feet tall, with the square stems and strong minty smell typical of the mint family [2]. Its paired leaves are large, oval, and coarsely toothed, ranging from green to deep purple and often purple-tinged or purple underneath ? the source of the "beefsteak" name [2]. It is easiest to identify from August into October, when it blooms: small white-to-pale-purple flowers line slender, spike-like clusters at the stem tips and where the leaves join the stem [2]. Crushing a leaf releases a strong, distinctive scent ? a quick confirmation that it is a mint-family plant [2].

At-a-glance cues:

1. Square stems and a strong minty smell when crushed (mint family) [2]
2. Paired, coarsely toothed oval leaves, green to deep purple and often purple underneath [2]
3. Small white-to-pale-purple flowers in slender, spike-like clusters, August through October [2]
4. Upright annual about 1.5 to 3 feet tall, often forming dense patches [2]

Leaves:

1. Arrangement: opposite (paired along the stem) [2]
2. Shape: broad, oval to egg-shaped with a pointed tip [2]
3. Margin: coarsely toothed [2]
4. Color: green to deep purple, often purple-tinged or purple beneath [2]
5. Odor: strongly aromatic when crushed [2]

Stems:

1. Habit: upright herbaceous annual, about 1.5 to 3 feet (0.5 to 1 m) tall, freely branching [2]
2. Square (four-sided) in cross-section, typical of the mint family [2]
3. Often tinged purple, with a strong odor [2]

Flowers:

1. Color: white to pale purple [2]
2. Shape: small and two-lipped, the typical mint-family flower [2]
3. Arrangement: in slender, spike-like clusters at the stem tips and where the leaves meet the stem [2]
4. Bloom time: August through October [2]

Fruit and seeds:

1. Fruit: tiny dry nutlets, typical of the mint family [2]
2. The plant reseeds abundantly and forms big patches; it spreads only by seed, with no runners [2]
3. Seeds are small and move easily in soil, water, and on equipment and animals; mature seed is also carried in late-cut hay [2][3]

Habitat:

Beefsteak plant is native to East and Southeast Asia, from the Himalayas and India east to China [1][2]. In North America it is not native; it was introduced as a culinary and ornamental herb and now grows wild, mainly across the mid-Atlantic and southeastern states [4][2]. It grows in sun to part shade and turns up in pastures, open woods and wooded bottomlands, along streams and trails, and on roadsides, railroads, and gravel bars [2]. It often gathers in the shady, disturbed ground around barns and field edges where livestock rest [3].

Reproduction:

Beefsteak plant is an annual that spreads only by seed ? it has no runners or creeping roots [2]. It reseeds heavily, so a few plants can become a large patch within a couple of years [2]. Seeds drop near the parent plant and also travel in soil and water, on mowing equipment, tools, and animals, and in hay cut late in the season [2][3]. Plants sprout in spring, grow through summer, flower and set seed from late summer into fall, then die with frost [2].

For control timing: pull, cut, or mow the plants before they flower and set seed in late summer, so they cannot reseed [2][3].

Impact and Damage:

The biggest concern with beefsteak plant is that it is poisonous to cattle, horses, goats, and other grazing animals [2][3]. It contains compounds called perilla ketones that, when eaten, cause fluid to build up in the lungs and lead to severe breathing trouble ? a condition stockowners call "panting disease," or acute respiratory distress ? which can kill the animal [3][2]. It is most dangerous in late summer and fall, when it is flowering and fruiting, and it stays toxic if it is cut and baled into hay [3]. Animals are most at risk when other forage is scarce and they are pushed to eat it, often in the shady spots where it grows, so keep it out of pastures and hayfields [3].

In a yard, it reseeds aggressively, so a planted patch can spread through the garden and beyond [2]. In natural areas it forms dense colonies in open woods, bottomlands, and along streams, crowding out native plants that cannot compete [2].

Similar species:

Garden coleus (Coleus scutellarioides) is the plant most often confused with beefsteak plant, since both are mint-family plants with showy purple, toothed leaves. Tell them apart by the leaf teeth and behavior: coleus has rounded teeth and is a tender ornamental that rarely escapes gardens, while beefsteak plant has sharply toothed leaves and spreads freely into the wild [2].

Monitoring and rapid response:

Signs to watch for:

1. Upright aromatic annual with square stems and purple-tinged, coarsely toothed leaves, often in dense patches [2]
2. Slender spike-like clusters of small white-to-purple flowers, August through October [2]
3. Patches in pastures, open woods, streamsides, and shady disturbed ground, especially near where livestock rest [2][3]

What you can do:

1. Because it is an annual that spreads only by seed, the goal is to stop seed: pull or hoe plants by hand ? they come up easily ? or cut or mow them before they flower in late summer [2][3]
2. Repeat for a couple of seasons to catch seedlings from seed already in the soil [2]
3. Bag and trash flowering or seeding plants rather than composting them [2]
4. Keep it out of pastures and hayfields, and do not bale hay from infested areas, since the dried plant stays toxic to livestock [3]
5. Natural area crews can pull or mow patches before seed set and revisit until the patch stops returning [2]

When to call a professional:

1. Large infestations across pasture, hayground, or natural areas where hand methods cannot keep up ? especially where livestock are at risk [3]
2. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Plants of the World Online (POWO), Royal Botanic Gardens, Kew. Perilla frutescens (L.) Britton. powo.science.kew.org
2. Missouri Department of Conservation. Beefsteak Plant (Perilla Mint), Field Guide. mdc.mo.gov
3. Mississippi State University Extension. Perilla Mint (Perilla frutescens). extension.msstate.edu
4. USDA NRCS PLANTS Database. Perilla frutescens (L.) Britton. plants.usda.gov

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