Herb · Poaceae
Lemongrass
Cymbopogon citratus
Sun, warmth, and a steady drink are about all lemongrass asks for, and it answers with fragrant stalks that keep coming all season long.
Full sun
Every 2–4 days
50–95°F · 10–35°C
75–100 days
Overview
Lemongrass is a tall tropical grass that's grown for the lemon-scented stalks down at its base, and those stalks are what flavor so much Southeast Asian cooking. It sends up a thick clump of arching blades that can hit 3 to 6 feet, and once the weather warms up it really gets going. Brush past it and the whole plant smells like fresh lemon.
It's a tropical plant through and through, so cold is its one weakness. Where winters stay mild, in zones 9 to 11, it just keeps coming back outdoors year after year as a perennial. Live somewhere colder? No problem, most folks either treat it as an annual or grow it in a pot they can bring indoors before the first frost.
The best part is that it barely asks for anything beyond sun, warmth, and water. Keep the soil moist, feed it through the growing season, and one little division fills out into a full clump in just a few months. Let it dry out or catch a frost, though, and the blades brown and the clump stalls, so those are the two things to stay ahead of.
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, plus a trip indoors before frost if you're somewhere cold.
Light
Lemongrass wants full sun, and honestly, the more the better, since it grows lush and upright in a bright, open spot. It'll put up with a little afternoon shade, but too much shade thins out the clump and takes some of the lemon punch out of the stalks.
Water
Keep the soil evenly moist and never let the pot dry out all the way, because this is a thirsty tropical grass. Water every 2 to 4 days when it's warm, more in real heat or in a pot, and mist the blades if the air's on the dry side.
Soil
Give it fertile, loamy soil that drains well but still holds some moisture, with plenty of organic matter mixed in. It's easygoing about acidity too, taking anything from a pH of 5.0 to 7.5.
Temperature
It's happiest in the warm range of 50°F to 95°F (10°C to 35°C) and grows fastest way up at the top end. Growth slows down as it dips toward 50°F, and a frost will kill it outright.
Humidity
Since it comes from humid tropics, lemongrass likes the air a bit damp, around 50% to 80%. In a dry climate or a heated room, mist the blades or set the pot on a humidity tray so the tips don't brown.
Feeding
Lemongrass is a hungry grass that loves a monthly feed through spring and early fall. Go with a balanced soluble fertilizer that leans high on nitrogen, since that's what fuels all that leafy growth.
Pruning
Trim off any dead or brown outer leaves to keep the clump neat, 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 for winter.
Repotting
Repot it once a year and divide the clump every 1 to 2 years, because it fills a container fast. When the roots circle the pot, shove the clump upward, or water just runs straight through, that's your cue to split it and freshen up the soil.
Size & spacing
A grown 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 fill out.
When to plant
Lemongrass wants warmth the whole way through and calls it quits at the first frost, so timing really matters here. Wait to set divisions or rooted stalks out until after the last spring frost, once nights stay above 50°F (10°C), and then you can harvest the thickened stalks once the clump fills in, roughly 3 to 4 months later. When the cold comes back, just dig it up or carry it indoors.
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 it's from dry air, a fungus, or a cold snap. Spot the early signs and you can jump in before the whole clump takes a hit. Find what matches below, then act while it still does some good.
Leaves suddenly limp and brown once a chilly night rolls through
Here's the thing: lemongrass is frost-tender, so it starts to struggle the moment things drop below about 50°F (10°C). If the damage popped up right after a cold night, that's your answer, and it isn't some disease. Get potted plants inside before frost hits, trim off the ruined foliage, and keep the clump somewhere warm and bright until spring rolls around.
Fix:
- Move potted plants indoors before frost
- Cut back damaged foliage and overwinter the clump in a warm, bright spot
Water racing through the pot while growth grinds to a halt
A lemongrass clump grows fast and packs a pot before you know it, so it goes rootbound and there's barely any soil left to hold water. If water pours straight through and the roots are shoving the clump up and out, that's the tell. Just split the clump into fresh soil or bump it into a bigger pot, and it'll take right off again.
Fix:
- Divide the clump and repot into fresh soil
- Move up to a larger container
Crunchy brown tips working their way down the leaf edges
Nine times out of ten it's just dry air, and that makes sense once you know lemongrass grew up in humid tropics and wants 50% to 80% humidity nearby. Letting the pot go dry between waterings does the same thing, and so does a crust of leftover fertilizer salt that burns the edges. So keep the soil evenly moist, mist on dry days, and flush the pot every now and then to wash those salts away.
Fix:
- Keep soil evenly moist
- Raise humidity or mist regularly in dry climates
- Flush the soil to remove salts and reduce feeding
Tiny orange spots on the leaves that smear when rubbed
What you're looking at is rust, a fungus that shows up when the leaves stay wet and the clump gets so packed that air can't move through. Want a quick check? Rub a blade, and if the powdery spots smear onto your fingers, that's it. Pull off the marked leaves, loosen up the clump so air gets in, and water down at the base so the foliage stays dry.
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 it's 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 closest, both because they handle the oils poorly and because a big mouthful of the fibrous blades can, once in a while, block the gut.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds
Safe for
People
Cats Mild
When a cat chews the blades, the citral oils usually leave it drooling, throwing up, and not much interested in food. Cats just can't break those oils down well, so concentrated lemongrass oil hits them harder, and if a cat gulps a big wad of the stringy grass, it can rarely end up with a blockage.
Dogs Mild
If a dog nibbles a leaf or stem, it usually gets a mild upset stomach, maybe a bit of vomiting or a loose stool that sorts itself out.
Horses Mild
A horse that grazes some of the grass might get a mild stomach upset, but that's about it in the small amounts most of them would bother with.
Rabbits Mild
Those same essential oils that bug cats and dogs can throw off a rabbit's sensitive gut too, so it's better as a once-in-a-while nibble than a regular green.
Livestock Caution
Grazing animals brush off a little just fine, but the cyanogenic glycosides pile up in bulk, so a big feed of the foliage is the part to keep an eye on.
Birds Caution
Birds are pretty touchy about plant oils, and the citral in lemongrass might not agree with them, so it's safest to keep pet birds away from the leaves.
People Culinary herb safe
Good news for cooks: lemongrass is a kitchen favorite, and the tender stalk bases are perfectly fine to cook and eat. The blades are just too tough and stringy to enjoy, not poisonous, so you trim them 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 pretty much grown as just one cooking type, the same one you'll find in the kitchen and at the garden center.
West Indian lemongrass
This is the everyday cooking type you'll run into, with blue-green blades and plump, lemon-scented stalk bases you cook with, and since it hardly ever sets seed, you grow more from divisions instead.
How to propagate
Lemongrass is about as easy as it gets to multiply, whether you split a clump you're already growing 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
Once a mature clump wakes up in spring, lift it and pull it apart into pieces that each hang onto roots and shoots, then get them back in the ground right away. Give it 2 to 4 weeks and they'll root in and start growing again. And here's a fun one: you can even stand rooted grocery-store stalks in water until roots show, then pot them up.
Myths
Lemongrass is a kitchen herb, so it must be safe around pets.
You'd think so, but the ASPCA lists lemongrass as toxic to cats, dogs, and horses, and chewing the leaves brings on an upset stomach. The bigger worry is concentrated lemongrass oil, especially for cats, since they can't break those oils down well.
Lemongrass is tough enough to make it through a cold winter outside.
Not really, since it's a frost-tender tropical that only sticks around outdoors in zones 9 to 11. Anywhere colder, grow it as an annual or dig the clump and keep it inside until things warm back up.