Herb · Poaceae
Lemongrass
Cymbopogon citratus
Give it full sun, steady moisture, and warmth, and lemongrass will reward you with fragrant stalks all season long.
Full sun
Every 2–4 days
50–95°F · 10–35°C
75–100 days
Overview
Lemongrass is a good-natured tropical grass grown for the lemon-scented stalks at its base, the very part that flavors so many Southeast Asian dishes. It sends up a full clump of arching blades that can reach 3 to 6 feet, and it picks up speed the moment the weather turns warm. Brush a hand across it and the whole plant releases a bright, fresh lemon scent that will make you glad you grew it.
This is a plant of the tropics with no head for cold, and knowing that is half the battle. Where winters stay gentle, in zones 9 to 11, it comes back outdoors year after year as a perennial. Anywhere colder, you can simply treat it as an annual or grow it in a pot you carry indoors before the first frost, and either way you will do fine.
Best of all, it asks for very little beyond sun, warmth, and water, so a nervous first-timer can relax. Keep the soil moist, feed it through the growing season, and a single small division fills out into a generous clump within a few months. The one thing to watch is letting it dry out or catching a frost, since that is when the blades brown and the clump stalls, and even then a bit of care usually sets it right.
Care
The short version: give it full sun, soil kept evenly moist and never bone dry, plenty of warmth, and a monthly feed through the growing season, and remember to bring it indoors before frost in cold climates.
Light
Lemongrass longs for full sun, and the more it gets the happier it looks, growing lush and upright in a bright, open spot. It will put up with a little afternoon shade if it must, but too much shade thins the clump and softens the lemon scent in the stalks.
Water
Keep the soil evenly moist and never let the pot go bone dry, since this thirsty tropical grass loves a steady drink. Water every 2 to 4 days in warm weather, more often in heat or in a container, and give the blades a mist wherever the air runs dry.
Soil
Give it fertile, loamy soil that drains freely yet still holds moisture, with a good helping of organic matter worked in. Happily, it is not fussy about acidity, and it takes anything from a pH of 5.0 to 7.5 in stride.
Temperature
It settles in nicely across the warm range of 50°F to 95°F (10°C to 35°C) and grows fastest toward the top of it. Growth eases off as it slips toward 50°F, and a frost will take the plant, so warmth is your friend here.
Humidity
Coming from the humid tropics, lemongrass enjoys the air on the damp side, around 50% to 80%. In a dry climate or a heated room, a quick mist of the blades or a pebble humidity tray under the pot keeps the tips from browning.
Feeding
Lemongrass is a hungry grass that welcomes a monthly feed through spring and early fall. Reach for a balanced soluble fertilizer on the higher side for nitrogen, which is exactly what fuels all that fresh, leafy growth.
Pruning
Snip off any dead or brown outer leaves to keep the clump looking tidy, and harvest the thick outer stalks by cutting them right at ground level. In cold climates, cut the foliage back before you bring the clump indoors to rest for winter.
Repotting
Plan to repot once a year and divide the clump every 1 to 2 years, since it does fill a container fast. When roots circle the pot, push the clump upward, or send water straight through, take it as a friendly nudge to split it 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 elbow room so air moves through the blades and the clump has space to bulk up into its full, handsome size.
When to plant
Lemongrass leans on warmth from beginning to end and gives up at the first frost, so let the season guide you. Set divisions or rooted stalks outside only after the last spring frost, once nights hold above 50°F (10°C), and you can look forward to harvesting the thickened stalks once the clump fills in, about 3 to 4 months later. When cold weather circles back, simply dig it or carry it indoors and it will be waiting for you next year.
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 turns up on the blades first, whether it comes from dry air, a fungus, or a sudden cold snap, and none of it needs to worry you. Catch the early signs and you can step in long before a whole clump suffers. Match what you notice to the list below, then act while your care still makes a difference.
Blades browning and flopping after a chilly night
This one is not your fault at all, since lemongrass is frost-tender and begins to struggle once things fall below about 50°F (10°C). When the damage shows up straight after a cold night, you can trust it was the cold and not a disease. Move potted plants inside before frost, snip away the spoiled foliage, and settle the clump somewhere warm and bright until spring returns.
Fix:
- Move potted plants indoors before frost
- Cut back damaged foliage and overwinter the clump in a warm, bright spot
Quick drying, stalled growth, and roots straining the pot
There is nothing wrong with your care here, since a happy lemongrass clump grows fast and fills its pot in no time, which leaves it rootbound with too little soil left to hold water. Water that pours straight through and roots that shove the clump up out of the pot both tell you the same thing. Split the clump into fresh soil or move it into a roomier home, and it will take off with new life.
Fix:
- Divide the clump and repot into fresh soil
- Move up to a larger container
Brown, crispy tips creeping in along the blades
Take heart, because dry air is almost always behind this, and it is easy to correct once you know lemongrass wants 50% to 80% humidity around it. Letting the pot go dry between drinks does the same, and a buildup of leftover fertilizer salts can nip the edges as well. Keep the soil evenly moist, mist on dry days, and flush the pot every so often to rinse the salts away, and your plant will bounce right back.
Fix:
- Keep soil evenly moist
- Raise humidity or mist regularly in dry climates
- Flush the soil to remove salts and reduce feeding
Orange-brown speckles dusting the blades
Those spots are rust, a fungus that settles in when the leaves stay wet and the clump grows so full that air cannot slip through. You can be sure of it by rubbing a blade, since the powdery specks will smear onto your fingers. Pick off the marked leaves, gently open the clump so air moves again, and water low at the base, and it will clear without much fuss.
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 and much-loved cooking herb, but the story changes for the animals in your home. 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 deserve the most watching, 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
If a cat chews the blades, the citral oils tend to leave it drooling, throwing up, and off its food for a while. Cats handle those oils poorly, so concentrated lemongrass oil is harder on them, and a big mouthful of the stringy grass can, in rare cases, lead to a blockage worth a vet call.
Dogs Mild
Should a dog nibble a leaf or stem, expect no more than a mild tummy upset, perhaps a little vomiting or a loose stool that clears up on its own.
Horses Mild
A horse that grazes some of the grass may feel a touch of stomach upset, and that is generally as far as it goes in the small amounts most would bother with.
Rabbits Mild
Those same essential oils that trouble cats and dogs can unsettle a rabbit's delicate gut, so treat it as an occasional nibble rather than a daily green.
Livestock Caution
Grazing animals brush off a small taste with no trouble, but the cyanogenic glycosides add up in bulk, so a large helping of the foliage is the thing to keep an eye on.
Birds Caution
Birds react easily to plant oils, and the citral in lemongrass may not agree with them, so it is kindest to keep pet birds away from the leaves just to be safe.
People Culinary herb safe
Rest easy in the kitchen, because lemongrass is a beloved cooking herb and the tender stalk bases are perfectly safe to cook and eat. The blades are simply too tough and fibrous to enjoy, not poisonous, so you trim them out for flavor and never 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
You will find lemongrass grown almost entirely as one welcoming culinary type, the same one waiting for you in the kitchen and at the garden center.
West Indian lemongrass
This is the friendly kitchen type you will most likely grow, with blue-green blades and plump, lemon-scented stalk bases for cooking, and because it rarely sets seed you simply raise more from divisions.
How to propagate
Lemongrass is one of the most forgiving plants to multiply, and whether you split a clump you already grow or root a stalk from the grocery store, success comes easily.
DivisionEasy
Spring, once growth resumes and temperatures are warm · 2-4 weeks to root and resume active growth
This is a wonderfully forgiving one to try. In spring, once a mature clump wakes up, ease it apart into sections that each hold roots and shoots, then tuck them back into the soil right away. In just 2 to 4 weeks they settle in and start growing again. You can even stand rooted grocery-store stalks in water until roots appear, then pot them up.
Myths
Lemongrass is a kitchen herb, so it must be harmless around pets.
As comforting as that sounds, the ASPCA lists lemongrass as toxic to cats, dogs, and horses, and a mouthful of the leaves brings on stomach upset. The real worry is concentrated lemongrass oil, especially for cats, whose bodies cannot break those oils down well.
Lemongrass is tough enough to survive a cold winter outdoors.
It is a frost-tender tropical that only overwinters outdoors in zones 9 to 11, so please do not count on it toughing out the cold. Anywhere chillier, grow it as an annual or lift the clump and keep it cozy indoors until warmth returns.