Herb · Poaceae
Lemongrass
Cymbopogon citratus
Give it full sun, steady moisture, and warmth, and lemongrass hands you fragrant stalks all season.
Full sun
Every 2–4 days
50–95°F · 10–35°C
75–100 days
Overview
Lemongrass is a tall tropical grass grown for the lemon-scented stalks at its base, the part that flavors so much Southeast Asian cooking. It throws up a dense clump of arching blades that can reach 3 to 6 feet, and it grows fast once the weather warms. Brush past it and the whole plant smells of fresh lemon.
It comes from the tropics and has no tolerance for cold. Where winters stay mild, in zones 9 to 11, it lives outdoors year after year as a perennial. Everywhere colder, gardeners treat it as an annual or grow it in a pot they can carry indoors before the first frost.
The plant asks for little beyond sun, warmth, and water. Keep the soil moist, feed it through the growing season, and a single division fills out into a full clump in a few months. Let it dry out or catch a frost, though, and the blades brown and the clump stalls.
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. Bring it indoors before frost in cold climates.
Light
Lemongrass wants full sun, the more the better, and grows lush and upright in a bright, open spot. It puts up with a little afternoon shade, but light shade thins the clump and weakens the lemon scent in the stalks.
Water
Keep the soil evenly moist and never let the pot dry out fully, since this is a thirsty tropical grass. Water every 2 to 4 days in warm weather, more in heat or in a container, and mist the blades where the air runs dry.
Soil
Plant in fertile, loamy soil that drains well yet holds moisture, with plenty of organic matter worked in. It is easygoing about acidity, taking anything from a pH of 5.0 to 7.5.
Temperature
It thrives in the warm range of 50°F to 95°F (10°C to 35°C) and grows fastest at the top end. Growth slows once it dips toward 50°F, and frost kills the plant outright.
Humidity
Coming from humid tropics, lemongrass likes 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 keep the tips from browning.
Feeding
Lemongrass is a hungry grass that responds to a monthly feed through spring and early fall. Use a balanced soluble fertilizer on the higher side for nitrogen, which is what drives all that leafy growth.
Pruning
Trim off any dead or brown outer leaves to keep the clump tidy, and harvest the thick outer stalks by cutting them at ground level. In cold climates, cut the foliage back before you bring the clump indoors for winter.
Repotting
Repot once a year and divide the clump every 1 to 2 years, since it fills a container fast. When the roots circle the pot, push the clump upward, or drain water straight through, it is time to split and refresh the soil.
Size & spacing
A mature clump stands 3 to 6 feet (90 to 180 cm) tall and spreads 24 to 35 inches (60 to 90 cm) across. Give it that much room so air moves through the blades and the clump has space to bulk up.
When to plant
Lemongrass needs warmth from start to finish and dies at the first frost. Set divisions or rooted stalks out only after the last spring frost, once nights stay above 50°F (10°C), then harvest the thickened stalks once the clump fills in, about 3 to 4 months later. Dig or carry it indoors before cold weather returns.
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 shows up on the blades first, whether from dry air, a fungus, or a cold snap. Read the early signs and you can step in before a whole clump suffers. Match what you see below, then act while it still helps.
Foliage browning and flopping after a cold snap
Lemongrass is frost-tender and starts to suffer once temperatures drop below about 50°F (10°C). Damage that shows up right after a cold night points straight to the cold rather than disease. Move potted plants indoors before frost, cut back the ruined foliage, and keep the clump in a warm, bright spot until spring.
Fix:
- Move potted plants indoors before frost
- Cut back damaged foliage and overwinter the clump in a warm, bright spot
Fast drying, stalled growth, and roots bursting the pot
A lemongrass clump grows fast and fills its container in a hurry, leaving the roots rootbound and the soil too thin to hold water. Water that runs straight through and roots that push the clump upward both confirm it. Divide the clump into fresh soil or step it up into a roomier pot, and the plant takes off again.
Fix:
- Divide the clump and repot into fresh soil
- Move up to a larger container
Brown, crispy tips and edges on the blades
Dry air is the usual culprit, since lemongrass comes from humid tropics and wants 50% to 80% humidity around it. Letting the pot dry out between waterings does the same damage, and a crust of leftover fertilizer salts can scorch the edges too. Keep the soil evenly moist, mist in dry weather, and flush the pot now and then to wash the salts away.
Fix:
- Keep soil evenly moist
- Raise humidity or mist regularly in dry climates
- Flush the soil to remove salts and reduce feeding
Orange-brown pustules speckling the blades
This is rust, a fungus that moves in when the leaves stay wet and the clump grows too crowded for air to pass through. Rub a blade and the powdery spots smear onto your fingers, which gives it away. Strip off the marked leaves, open up the clump so air can move, and water at the base to keep the foliage dry.
Fix:
- Remove and destroy affected leaves
- Improve air circulation around the clump
- Water at the base rather than overhead
Toxicity
Lemongrass is a safe, much-loved cooking herb for people, but it is a different story 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 are the ones to watch most, both because they handle the oils poorly and because a big mouthful of the fibrous blades can rarely block the gut.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Mild
The citral oils in the blades usually bring on drooling, vomiting, and a poor appetite. Cats break those oils down badly, so concentrated lemongrass oil hits them harder, and a cat that grazes a big mouthful of the fibrous grass can rarely end up with a blockage.
Dogs Mild
A dog that nibbles the leaves or stems tends to get a mild stomach upset, with some vomiting or loose stool that passes on its own.
Horses Mild
Eating the grass can leave a horse with a mild bout of stomach upset, nothing more in the small amounts most would touch.
Rabbits Mild
The same essential oils that bother cats and dogs can unsettle a rabbit's sensitive gut, so it is best kept as a rare nibble rather than a regular green.
Livestock Caution
Grazing animals shrug off a little, but the cyanogenic glycosides build up in quantity, so a large feed of the foliage is the part to watch.
Birds Caution
Birds are touchy about plant oils, and the citral in lemongrass may not sit well, so steer pet birds away from the leaves to be safe.
People Culinary herb safe
Lemongrass is a kitchen staple, and the tender stalk bases are safe to cook and eat. The blades are 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 is grown almost entirely as one culinary type, the one you find in the kitchen and the garden center.
West Indian lemongrass
The standard culinary type carries blue-green blades and swollen, lemon-scented stalk bases that you cook with, and since it seldom sets seed it is grown from divisions rather than seed.
How to propagate
Lemongrass is among the easiest plants to multiply, whether you split a clump you already grow or root a stalk 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 once it wakes up, pull it into sections that each keep roots and shoots, and replant them straight away. Within 2 to 4 weeks they root in and start growing again. You can also stand rooted stalks from the grocery store in water until roots show, then pot them up.
Myths
Lemongrass is a kitchen herb, so it is harmless around pets.
The ASPCA lists lemongrass as toxic to cats, dogs, and horses, and chewing the leaves brings on stomach upset. Concentrated lemongrass oil is the real danger, especially for cats, which cannot break the oils down well.
Lemongrass is tough enough to live through a cold winter outdoors.
It is a frost-tender tropical that only winters over outdoors in zones 9 to 11. Anywhere colder, grow it as an annual or dig the clump and keep it indoors until the weather warms.