Herb · Lamiaceae
Spearmint
Mentha spicata
Give it moist soil and a pot to call its own, and spearmint will hand you fresh leaves all season.
Full sun
Every 2–4 days
59–77°F · 15–25°C
80–90 days
Overview
Spearmint is the everyday garden mint behind sauces, teas, and a cool sprig in a glass. It belongs to the mint family and grows as a hardy perennial, dying back in winter and surging up again each spring with bright, toothed leaves and a clean, sweet scent. Few herbs are this easy to grow, which is both its charm and its catch.
The plant runs on underground runners that creep outward and root as they go, so a single start can fill a bed faster than you expect. Most gardeners grow it in a sunken pot, a raised bed of its own, or behind a deep root barrier. Hand it that one boundary and it asks for almost nothing else.
Regular cutting is what keeps spearmint at its best. Pinch the tips often and you get a low, bushy plant thick with tender leaves; let it run to flower and the stems turn leggy while the flavor fades. Pick early and pick often, and it rewards you right up to the first hard frost.
Care
The short version: full sun to a little shade, soil kept evenly moist and never bone dry, and a contained spot so the runners can't wander. Pinch the tips often to keep it bushy.
Light
Spearmint grows best in full sun, which keeps it compact and concentrates the oils that give the leaves their flavor. It also takes partial shade without complaint, handy in hot regions where afternoon cover keeps it from wilting.
Water
Keep the soil evenly moist and never let it dry out, since spearmint sulks the moment it goes thirsty. Plan to water every 2 to 4 days, and more often in a heat wave or in a container, which loses moisture fast.
Soil
Plant it in rich, loamy soil full of organic matter that holds water without turning to mud. A pH of 6.0 to 7.0 suits it, sitting right around neutral.
Temperature
Spearmint is happiest between 59°F and 77°F (15°C to 25°C) and grows fastest in those mild conditions. It shrugs off winter cold by dying back to the roots and returning in spring.
Humidity
Average air around 40% to 70% keeps the foliage healthy and lush. Very dry air invites spider mites, so a moist root zone and the odd misting help in a hot, dry spell.
Feeding
A single feed of balanced fertilizer or compost in spring carries the plant through the season. Go easy on the nitrogen, since too much pushes soft growth and waters down the oils that make the leaves taste of anything.
Pruning
Pinch and harvest the tips often to keep the plant bushy rather than leggy, and cut it back hard after flowering to bring on fresh growth. Snip off flower spikes as they form, because once a stem blooms its leaves lose their punch.
Repotting
In a container, repot every 1 to 2 years or as soon as it turns rootbound, splitting the clump while you're at it. Roots circling the pot edge, soil that dries almost at once, and shrinking leaves all say it's time.
Size & spacing
Spearmint stands 12 to 24 inches (30 to 60 cm) tall but spreads wider, reaching 24 to 35 inches (60 to 90 cm) across as the runners travel. Give it room, or better still a container, so it doesn't crowd whatever grows beside it.
When to plant
Spearmint is a hardy perennial that takes the cold of zones 5 through 9 in its stride. Set plants out in spring once hard frost has passed, harvest leaves all through the growing season, and pinch off the flower spikes in summer to keep the leaves sweet.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Late winter to early spring (though division/cuttings are more reliable than seed)
- Plant: Spring, after danger of hard frost
- Harvest: Harvest leaves throughout the growing season; pinch off flower spikes in summer to preserve leaf quality
Hardiness
USDA hardiness zones: 5–9
Temperature: down to -29°C
Troubleshooting
Spearmint is tough, so most of its trouble is foliage disease, a few hot-weather pests, and its own habit of spreading too far. Match what you see below and step in early, while a quick fix still does the job.
Rusty orange pustules dotting the undersides of leaves
This is mint rust, a fungus that takes hold when foliage stays wet and crowded. Strip off the spotted leaves and bin them rather than composting, then thin the plant so air can move through it. A badly hit clump can be cut right back to the ground and will push up clean growth.
Fix:
- Remove and destroy infected foliage (do not compost)
- Improve air circulation by thinning crowded growth
- Avoid overhead watering to keep foliage dry
- Cut back severely affected plants to ground level
Speckled, fading leaves with fine webbing underneath
Spider mites move in when the air turns hot and dry, draining the leaves until they look dusty and pale. Blast them off with a strong jet of water, then keep the soil moist and the humidity up to make the plant a poor home for them. Insecticidal soap clears a heavy outbreak.
Fix:
- Rinse foliage with a strong spray of water
- Raise humidity and keep soil moist
- Apply insecticidal soap if severe
Mint creeping out and swallowing the rest of the bed
Spearmint travels on underground runners that surface as new shoots well away from the parent, and left alone it will take over. The simplest fix is to grow it in a buried bottomless pot or a bed of its own, or sink a root barrier at least 30 cm deep. Dig out any runner that escapes before it roots in.
Fix:
- Grow in a buried bottomless container or dedicated bed
- Sink physical root barriers 30+ cm deep
- Dig out and remove escaped runners promptly
Smaller leaves and weak growth from a matted clump
An old clump packs itself with tangled roots and runners until the center gives out and the leaves shrink. Lift it, split off the healthy outer sections, and replant them in fresh soil while throwing away the woody middle. Dividing every two to three years keeps the plant cropping well.
Fix:
- Divide the clump and replant healthy sections
- Refresh soil and discard the woody center
Toxicity
Spearmint is a culinary herb that people eat happily, so there's no worry at the table. The catch is its essential oils, which can give cats, dogs, and horses a mild stomach upset if they eat a large amount, so keep grazing pets away from a full plant.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Mild
A cat that nibbles a little leaf is usually fine, but a big mouthful of the oily foliage can bring on drooling, vomiting, and loose stools.
Dogs Mild
Dogs that chew through a quantity of leaves may end up with an upset stomach, some vomiting, and diarrhea that passes on its own.
Horses Mild
A horse that grazes a large amount can get a mild bellyache and soft droppings from the concentrated oils.
Rabbits Caution
A few leaves now and then sit fine, but the strong oils mean a rabbit shouldn't make a meal of it.
Livestock Caution
Goats, sheep, and cattle rarely seek mint out, and a casual browse does little harm, though a gut full of it can loosen digestion.
Birds Caution
Most birds leave the pungent leaves alone; offer only a token amount, since the oils are stronger than a small body wants.
People Safe
Spearmint is a kitchen herb that people have eaten for centuries, safe in teas, sauces, and salads with no concern at culinary amounts.
Normal culinary amounts of spearmint leaf used in food are not a concern; the risk relates to ingestion of large quantities of the plant or concentrated essential oils.
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
Most spearmint sold is the plain species, but a couple of named types are worth seeking out for flavor or looks.
Mentha spicata 'Kentucky Colonel'
Large, crinkled leaves carry an unusually strong spearmint flavor that makes this the classic pick for juleps and the kitchen.
Mentha spicata var. crispa (Curly mint)
Tightly ruffled, curled leaf edges give this one a frilly look while it keeps the familiar clean spearmint aroma.
How to propagate
Spearmint is one of the simplest plants to multiply, and most gardeners skip seed entirely in favor of splitting a clump or rooting a cutting.
DivisionEasy
Spring or autumn · 2 to 4 weeks
Dividing is the surest way to make more spearmint. In spring or autumn, lift an established clump and pull it into sections that each carry a piece of runner with its own roots and shoots, then replant them. Each piece settles in and takes hold within 2 to 4 weeks.
Stem cuttingsEasy
Spring through summer · 1 to 2 weeks
Spearmint roots so willingly that a cutting barely needs coaxing. Anytime from spring through summer, snip a healthy stem tip and stand it in a glass of water or push it into moist soil, and roots appear in 1 to 2 weeks before you move it on.
Myths
Mint is harmless in the garden because it is just a small herb.
Its size is no guide to its manners. Spearmint runs underground and can swallow a whole bed in a season or two, so plant it in a buried pot or behind a root barrier rather than loose in the ground.