Herb · Lamiaceae
Peppermint
Mentha × piperita
Constant moisture and a pot all to itself keep peppermint's dark, toothed, menthol-cool leaves coming in a steady flush.
Full sun
Every 2–4 days
80–90 days
USDA 3–8
Overview
Peppermint is a hardy perennial herb, a natural cross between watermint and spearmint, and its build gives it away at a glance. The stems rise square-sided and stiff, hung with dark green, toothed leaves that release a cool menthol scent the instant a finger crushes them. It grows in full sun to partial shade and rides out cold down to USDA zone 3.
Watch the plant closely and its spread reads in the growth itself. From the base it throws pale underground and surface runners, each one creeping outward and lifting a fresh tuft of square stems and dark leaves wherever it roots. In summer the shoots stretch up into slim flower spikes, small and soft-hued above the foliage, which is why the spikes are pinched off to hold the leaves at their best.
Because it is a sterile hybrid, peppermint will not come true from seed, so a division or a stem cutting starts the next plant. The stems root with almost no coaxing, sending fine white roots from their lower nodes. One healthy plant fills a pot with dense, dark, menthol-scented leaves, edges a path, or crowds a windowsill in short order.
Care
The short version: full sun to part shade, soil kept evenly moist and never bone dry, and a pot or buried barrier to hold the pale runners in check.
Light
Peppermint colors deepest in full sun, where the leaves stay dark and dense, yet it holds up in partial shade where summers run hot and dry. Full sun sharpens the menthol in the foliage, while a little shade lets the soil hold the moisture the leaves lean on.
Water
Keep the soil consistently moist and never let it dry, since a thirsty plant drops its leaves flat and loses the crisp menthol scent. Water every 2 to 4 days, and more often for a pot or through hot, dry weather.
Soil
Root it in rich, moisture-retentive loam thick with organic matter. A pH between 6.0 and 7.0 suits it, and soil that stays damp without waterlogging keeps the dark leaves pushing up steadily.
Temperature
Peppermint is tough, coming through anything from -29°F to 84°F (-34°C to 29°C). The leafy top dies back in winter, and pale shoots break from the roots again each spring, which is what carries it through cold zones.
Humidity
Average humidity around 40% to 70% keeps the leaves plump and glossy. Air moving between the stems matters more than the exact figure, since stale, crowded air is what lets rust dust the leaves and mites veil them in webbing.
Feeding
Feed lightly through spring and summer with a balanced fertilizer or a little compost or aged manure. Hold back on nitrogen, because too much swells soft, watery leaves with thinner oils and a fainter menthol note.
Pruning
Pinch and harvest the stem tips often to keep the plant bushy and thick-leaved rather than leggy. Snip off the slim flower spikes to keep the leaves tender, and shear the whole plant back hard after bloom to bring a flush of fresh dark growth.
Repotting
Peppermint packs a pot with roots fast, so repot it every 1 to 2 years, or sooner when roots circle the wall, leaves come in small, or pale runners nose out the drainage holes. Splitting the clump as you go keeps the leaves large.
Size & spacing
The leafy stems stand 12 to 35 inches (30 to 90 cm) tall and the runners fan the plant out 1.5 to 4 feet (45 to 120 cm) wide. Give each one room, or a pot, so the spreading mat of stems stays in bounds.
When to plant
Peppermint is tough and cold-hardy, so its timing is relaxed next to tender crops. Set out divisions or rooted cuttings in spring once the last frost has passed, then strip leaves right through the growing season, pinching off the slim summer flower spikes as they rise to keep the dark foliage tender and full-flavored.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Spring, after the last frost, from divisions of runners or rooted stem cuttings
- Harvest: Harvest leaves throughout the growing season; pinch off flower spikes (summer bloom) to maintain leaf quality
Hardiness
USDA hardiness zones: 3–8
Temperature: down to -40°C
Troubleshooting
Peppermint is easygoing, so most of its troubles read right on the plant itself: dull or spotted leaves from wet, crowded growth, or pale runners escaping past its edge. Look closely at the foliage and the margins of the bed and the early signs stand out plainly. Match what you see below, then act while it still helps.
Limp, yellowing stems dying off down one side
Verticillium wilt rises out of the soil and clogs the stems from within, so one side of the plant droops and yellows while the rest looks on, and the collapse deepens as the days grow hot. Snap or slice a wilting stem and brown streaks run through the pale tissue inside. Nothing brings it back once it has entered the stems, so lift and destroy the plant, set healthy stock in clean, uninfested soil, and keep mint off any ground where it has struck before.
Fix:
- Remove and destroy affected plants
- Do not replant mint or other susceptible crops in the same soil
- Plant resistant mint stock in fresh, uninfested soil
Raised rust-orange dots freckling the backs of the leaves
Turn a leaf over and the raised orange to brown pustules dusting its underside are mint rust, a fungus that settles in where the foliage stays wet and the stems press close. Pick off each spotted, yellowing leaf the moment those powdery specks appear, thin the stems so air slips between them, and wet the soil rather than the leaves. When the spotting runs through the whole stand, cut it to the ground, clear the fallen debris, and let clean new leaves push up.
Fix:
- Remove and destroy infected foliage immediately
- Improve air circulation by thinning crowded stems
- Avoid overhead watering and wetting foliage
- Cut affected plants to the ground and dispose of debris in severe cases
Fresh mint shoots popping up all across the bed
The pale, cord-like runners snaking out below and across the soil are runner spread, the plant's own way of traveling. Each runner roots down and lifts a new tuft of square-stemmed shoots wherever it lands, so a single leafy clump becomes a dense green sheet in a season or two. Pen those runners in with a pot or a buried bottomless container, tug out the ones that slip past, and cut a deep edge around the bed so they meet a wall of soil.
Fix:
- Grow in containers or buried barriers to confine roots
- Regularly dig out and remove escaped runners
- Edge beds deeply and monitor margins each season
A matted, hardened clump whose leaves keep getting smaller
In an old stand the center hardens into a congested, woody clump, its heart bare and stiff while a matted ring of runners crowds the outer edge and the leaves come in smaller. Lift the whole mass and the tangle of pale roots and runners spills out in your hands. Every 2 to 3 years, pull it apart, toss the woody core, replant the fresh outer pieces with their bright young shoots, and fold compost into the loose soil so full leaves return.
Fix:
- Divide the clump every 2-3 years
- Discard old woody center and replant vigorous outer divisions
- Refresh soil with compost at replanting
Pinprick yellow speckles and gauzy threads over the leaves
Leaves that turn dull and dusty, freckled with pale yellow stippling and veiled in thin webbing, are the mark of spider mites that move in when the air runs hot and dry. Hold a leaf over white paper, tap it, and the specks that drop and crawl are the mites themselves. Knock them loose with a hard jet of water, coat the leaf undersides with insecticidal soap or horticultural oil, and keep the soil watered so the parched conditions they favor never settle around the plant.
Fix:
- Spray foliage with a strong jet of water to dislodge mites
- Apply insecticidal soap or horticultural oil to undersides of leaves
- Increase humidity and keep plants well watered
Toxicity
Peppermint is a culinary herb, so its cool, menthol-scented leaves are perfectly safe for people to eat and brew. For pets the oils packed in those leaves make it a mild hazard to cats, dogs, and horses, bringing on vomiting or diarrhea if they eat much, and concentrated peppermint oil is far more dangerous than the plant itself. Keep grazing animals away from large leafy stands, and keep the oil away from cats entirely.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Mild
A single leaf plucked and chewed usually passes, but a real mouthful of the oil-rich foliage can bring vomiting and diarrhea. Cats feel it worst, since they lack the liver enzymes to break those essential oils down, so the sharpest danger is concentrated peppermint oil rather than the leaf. Keep that oil away from them completely.
Dogs Mild
A few of the dark leaves rarely trouble a dog, but one that strips a whole plant can end up with vomiting and diarrhea from the oils packed in the foliage. Watch for drooling or a dull appetite, and keep concentrated oils out of reach.
Horses Mild
A little of the aromatic foliage grazed from pasture is usually shrugged off, though a horse that eats a large amount may get an upset stomach and loose droppings from the oils. Keep them off large leafy stands.
Rabbits Mild
The same pungent oils that fill the leaves and bother cats and dogs can unsettle a rabbit's sensitive gut, so this is no free-choice green. Offer just a leaf or two now and then and watch for soft stool.
Livestock Mild
Goats, sheep, and cattle can browse a little of the strong-scented foliage without harm, but a big mouthful of the oily leaves can bring on digestive upset. Treat it as an occasional taste rather than fodder.
Birds Caution
There is little firm data on mint and pet birds, and the potent oils held in the leaves are reason enough for care. Keep it off the regular menu and keep any essential oil well clear of the cage.
People Safe
For people the cool, menthol-scented leaves are good to eat fresh, dried, or steeped as tea. The only real caution is the concentrated essential oil pressed from them, which is far stronger than the leaf and not for casual use.
Concentrated peppermint essential oil is a significantly greater hazard, especially to cats, which lack the liver enzymes to metabolize it; keep essential oils away from pets.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
United Kingdom
Animal PoisonLine: 01202 509000 (fee applies)
Australia
Animal Poisons Helpline: 1300 869 738
Varieties
The named peppermint types read apart mostly by the color of their stems and leaves and the strength of their menthol. These are the ones worth knowing.
Chocolate mint
Dark-tinged stems and leaves carry a warm chocolate-peppermint scent that sends it into desserts and tea.
Black peppermint
Deep purple-tinged stems and dark foliage set off this high-menthol type prized for its bold flavor.
White peppermint
Greener stems and paler leaves give this softer-looking one a milder, sweeter taste than its darker cousins.
How to propagate
Peppermint will not grow true from seed, but its square, leafy stems root with ease, whether you split a clump of runners or stand a few cuttings in a glass of water.
DivisionEasy
Spring or early autumn · 2 to 4 weeks
Division is the surest way to make more peppermint, since this sterile cross will not grow true from seed. In spring or early autumn, lift the clump and tease it apart into sections, each holding a length of pale rooted runner and a tuft of shoots, then set those pieces back into the soil. They take hold and push new leaves within 2 to 4 weeks.
Stem cuttingsEasy
Spring through summer · 1 to 3 weeks
Cuttings root just as readily and copy the parent exactly, which matters with a sterile hybrid like this. Cut 10 to 15 cm lengths of square, leafy stem anytime from spring through summer and stand them in water or moist mix. Fine white roots break from the lower nodes in 1 to 3 weeks, and the new plant is ready to pot on.
Myths
You can grow true peppermint from seed.
Peppermint is a sterile cross of watermint and spearmint, so it sets little or no viable seed, and any seedlings that do sprout will not be true peppermint. The only way to keep the plant true is to propagate it vegetatively, by splitting the clump or rooting cuttings taken from its stems.
A leaf that flavors human dishes cannot upset an animal's stomach.
Safe in the kitchen does not mean safe in a pet's stomach. The ASPCA lists mint as toxic to cats, dogs, and horses, where the essential oils in the leaves cause vomiting and diarrhea, and concentrated peppermint oil is far more dangerous, especially to cats that cannot break it down.