Herb · Poaceae
Lemongrass
Cymbopogon citratus
Pile on the sunshine, keep the moisture steady, and hold the warmth, and lemongrass sprints toward a season-long supply of fragrant stalks.
Full sun
Every 2–4 days
50–95°F · 10–35°C
75–100 days
Overview
Lemongrass shoots up as a tall tropical grass grown for the lemon-scented stalks at its base, the very part that flavors so much Southeast Asian cooking. It launches a dense clump of arching blades that can climb to 3 to 6 feet, and it takes off fast the moment the weather warms. Brush a hand across it and the whole plant snaps with fresh lemon.
It hails from the tropics and simply will not take cold. Where winters stay mild, in zones 9 to 11, it powers back outdoors year after year as a perennial. Everywhere colder, growers run it as an annual or plant it in a pot they can whisk indoors before the first frost.
Best of all, it asks for little beyond sun, warmth, and water, so it pays you back quickly. Keep the soil moist, feed it through the growing season, and one small division swells into a full clump in a matter of months. Let it dry out or catch a frost, though, and the blades brown and the clump stalls, so stay a step ahead of both.
Care
The short version: full sun, soil kept evenly moist and never bone dry, plenty of warmth, and a monthly feed through the growing season, and whisk it indoors before frost in cold climates.
Light
Lemongrass hungers for full sun, the more the better, and it shoots up lush and upright in a bright, open spot. It puts up with a little afternoon shade, but heavier shade thins the clump and drains the lemon scent from the stalks.
Water
Keep the soil evenly moist and never let the pot dry out fully, since this thirsty tropical grass drinks hard. Water every 2 to 4 days in warm weather, more in heat or in a container, and mist the blades where the air turns dry.
Soil
Plant it in fertile, loamy soil that drains well yet holds moisture, packed with organic matter. It shrugs off acidity worries, taking anything from a pH of 5.0 to 7.5.
Temperature
It roars along in the warm range of 50°F to 95°F (10°C to 35°C) and grows fastest right at the top end. Growth eases off as it slides toward 50°F, and frost kills the plant outright.
Humidity
Fresh from humid tropics, lemongrass wants the air on the damp side, around 50% to 80%. In dry climates or a heated room, mist the blades or set the pot on a humidity tray to hold the tips from browning.
Feeding
Lemongrass is a hungry grass that leaps on a monthly feed through spring and early fall. Reach for a balanced soluble fertilizer on the higher side for nitrogen, the fuel behind all that leafy growth.
Pruning
Snip off any dead or brown outer leaves to keep the clump crisp, and harvest the thick outer stalks by slicing them at ground level. In cold climates, cut the foliage back before you haul the clump indoors for winter.
Repotting
Repot once a year and divide the clump every 1 to 2 years, since it packs a container fast. When roots circle the pot, shove the clump upward, or send water straight through, jump on it and split and refresh the soil.
Size & spacing
A mature clump towers 3 to 6 feet (90 to 180 cm) tall and spreads 24 to 35 inches (60 to 90 cm) across. Hand it that much room so air rushes through the blades and the clump has space to bulk up.
When to plant
Lemongrass runs on warmth from start to finish and drops at the first frost, so time it right and it rewards you. Set divisions or rooted stalks out only after the last spring frost, once nights hold above 50°F (10°C), then harvest the thickened stalks once the clump fills in, about 3 to 4 months later. Dig it or haul it indoors before cold weather sweeps back in.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: After the last spring frost, once soil and nights are warm (above about 10°C / 50°F)
- Harvest: Rarely flowers in cool climates; harvest the thickened stalks once the clump is established, about 3-4 months after planting
Hardiness
USDA hardiness zones: 9–11
Temperature: down to -7°C
Troubleshooting
Most lemongrass trouble breaks out on the blades first, whether from dry air, a fungus, or a cold snap. Catch the early signs and you can leap in before a whole clump takes a hit. Match what you spot below, then move while it still counts.
Whole clump sagging and browning after one cold night
Lemongrass is frost-tender and starts to falter the second temperatures dive below about 50°F (10°C). Damage that lands right after a cold night points dead at the chill, not a disease. Rush potted plants indoors before frost, snip off the ruined foliage, and park the clump in a warm, bright spot, and it charges back come spring.
Fix:
- Move potted plants indoors before frost
- Cut back damaged foliage and overwinter the clump in a warm, bright spot
Roots cramming the pot while growth stalls and water disappears fast
A lemongrass clump races along and packs its container in no time, which leaves it rootbound with too little soil to hold water. Water that shoots straight through and roots that heave the clump upward both call it. Split the clump into fresh soil or bump it into a bigger pot, and it leaps back into growth.
Fix:
- Divide the clump and repot into fresh soil
- Move up to a larger container
Blade tips crisping brown while the edges scorch
Dry air is the usual troublemaker here, which tracks, since lemongrass grew up in humid tropics and craves 50% to 80% humidity around it. A pot that dries out between waterings pushes the same browning, and a crust of leftover fertilizer salt will nip the edges too. Keep the soil evenly moist, mist through dry spells, and flush the pot every so often to sweep the salts out, and the blades green right back up.
Fix:
- Keep soil evenly moist
- Raise humidity or mist regularly in dry climates
- Flush the soil to remove salts and reduce feeding
Powdery orange pustules breaking out across the blades
Meet rust, the fungus that pounces when leaves stay wet and the clump packs in too tight for air to travel. Rub a blade and the powdery spots smear onto your fingers, and there is your proof. Strip off the marked leaves, open the clump so air rushes through, and aim water at the base to keep the foliage dry, and it clears fast.
Fix:
- Remove and destroy affected leaves
- Improve air circulation around the clump
- Water at the base rather than overhead
Toxicity
For people, lemongrass is a safe, much-loved cooking herb, but the tale turns for pets. The ASPCA lists it as toxic to cats, dogs, and horses, since the essential oils and cyanogenic glycosides in the grass upset the stomach. Cats top the watch list, both because they handle the oils poorly and because a big mouthful of the fibrous blades can, in rare cases, block the gut.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Mild
Chew on the blades and the citral oils set a cat drooling, vomiting, and turning up its nose at food. Cats handle those oils poorly, so concentrated lemongrass oil lands hardest on them, and a cat that wolfs a big mouthful of the fibrous grass can, in rare cases, wind up with a blockage.
Dogs Mild
A dog that grabs a nibble of the leaves or stems usually walks off with nothing worse than a mild stomach upset, a touch of vomiting or a loose stool that clears on its own.
Horses Mild
Grazing the grass can hand a horse a mild bout of stomach upset, and little beyond that at the small amounts most would bother to take.
Rabbits Mild
Those same essential oils that rattle cats and dogs can throw a rabbit's sensitive gut off balance, so keep it to a rare nibble rather than a regular green.
Livestock Caution
Grazing animals brush off a small taste, but the cyanogenic glycosides stack up in bulk, so a big feed of the foliage is the one to watch.
Birds Caution
Birds react fast to plant oils, and the citral in lemongrass may not settle well, so steer pet birds clear of the leaves to play it safe.
People Culinary herb safe
Cooks, rejoice: lemongrass is a kitchen star, and the tender stalk bases are safe to cook and eat. The blades are just tough and fibrous rather than poisonous, so trim them out for flavor, not for safety.
Small culinary amounts of the stalk are typically low risk; concentrated lemongrass essential oil is the bigger hazard, especially for cats, which do not metabolize the oils well.
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
Lemongrass runs almost entirely as one cooking type, the same one waiting for you in the kitchen and at the garden center.
West Indian lemongrass
This is the go-to cooking type most growers reach for, decked in blue-green blades and plump, lemon-scented stalk bases for the kitchen, and since it rarely sets seed, you multiply it from divisions instead.
How to propagate
Lemongrass ranks among the easiest plants to multiply, whether you split a clump you already grow or root a stalk straight from the grocery store.
DivisionEasy
Spring, once growth resumes and temperatures are warm · 2-4 weeks to root and resume active growth
Lift a mature clump in spring the moment it stirs, tear it into sections that each grip roots and shoots, and plant them back right away. In just 2 to 4 weeks they grab hold and take off growing again. Better yet, stand rooted grocery-store stalks in water until roots pop out, then pot them up for a whole new clump.
Myths
A herb that stars in the kitchen surely cannot trouble a dog or cat.
Tempting to believe, but the ASPCA lists lemongrass as toxic to cats, dogs, and horses, and chewing the leaves sets off stomach upset. The real danger is concentrated lemongrass oil, especially for cats, which cannot break the oils down well.
Lemongrass is tough enough to power through a cold winter outdoors.
Not a chance, since this frost-tender tropical only winters over outdoors in zones 9 to 11. Anywhere colder, grow it as an annual or dig the clump and stash it indoors until the weather warms.