Growing Lemongrass in Pots (and Overwintering It)

Growing lemongrass in pots is the practical way to grow this tropical grass outside the warmest climates. Lemongrass (Cymbopogon citratus) loves heat, sun and water, and it dies in hard frost. In a container, you can give it a full summer outdoors, then carry it inside before the cold arrives.

The catch is size. Lemongrass is a big, fast clump in hot weather, so it needs a larger pot, more water and more feeding than most kitchen herbs. This guide covers starting plants, potting, care, harvesting, overwintering and dividing.

Quick answer: Start from rooted grocery stalks or a nursery plant after your last frost, in a large pot with drainage holes and full sun. Keep the mix evenly moist and feed every 1 to 3 weeks in summer, harvest stalks once they're 1/2 inch (1.3 cm) thick, and bring the pot indoors before nights drop below 45°F (7°C).

Where lemongrass is hardy (and where it needs a pot)

NC State Extension lists lemongrass as hardy in USDA zones 8b to 11b. Everywhere colder, it's a tender perennial: Utah State University Extension notes it's commonly grown as an annual in cool areas and recommends containers so the plant can come indoors in fall.

Temperature thresholds matter more than the zone map for a pot you can move. The RHS gives two numbers worth remembering:

• 55°F (13°C): the minimum lemongrass needs to grow.
• 45°F (7°C): bring the plant in before night temperatures drop below this.

That means even gardeners in mild zones may see it stall in a cool spring. Utah State notes that growth is slow until summer heat arrives, then picks up dramatically.

Grocery stalks, nursery plants or seed

There are three ways to get a plant, and they suit different situations.

Rooting stalks from the store

Many growers start with lemongrass bought for cooking. Utah State says fresh stalks from grocery stores, especially those selling Asian ingredients, will root in a glass of water in about 2 weeks. University of Illinois Extension agrees that grocery stalks can often be rooted.

From grocery stalk to potted lemongrass in four steps.

1. Choose firm, fresh stalks with the bulb-like base still attached. Toronto Master Gardeners advise looking for an intact root plate at the base.
2. Stand them base-down in a glass with a little water on a bright windowsill.
3. Change the water often so it stays fresh, and wait for roots.
4. Pot them up once roots form, planting at the depth where the roots start.
5. Move the pot outside after your last frost. Toronto Master Gardeners wait until nights are reliably above 50°F (10°C).

The RHS takes a more cautious line. It advises against planting stems bought from supermarkets or food shops because of the risk of bringing in plant diseases. If you'd rather avoid that risk, a nursery plant is the safer start.

Pot size and potting mix

Lemongrass gets big. Utah State describes plants reaching 3 to 6 feet (about 0.9 to 1.8 m) tall and about 3 feet (0.9 m) wide in good conditions, while NC State gives a more modest 2 to 4 feet (0.6 to 1.2 m) tall. The RHS notes plants rarely reach full size in pots, which is useful if you'll be bringing it indoors.

None of the extension guides we checked give an exact pot size for lemongrass. For comparison, the University of Maryland Extension sets a minimum of 4 to 6 gallons (15 to 23 L) of mix and 8 to 12 inches (20 to 30 cm) of depth for medium herbs such as rosemary. Lemongrass grows larger than those, so treat that as the floor when growing lemongrass in pots, and plan on a bigger tub as the clump fills out. When you repot, the RHS suggests moving up to a container slightly wider and deeper than the current one.

Before picking a pot, think about winter. A huge tub is great on a patio in July, but you'll need to carry it indoors in fall. Dividing the clump each spring (covered below) keeps it a manageable size.

For the mix:

• Use a rich potting mix with drainage holes in the pot. Illinois Extension recommends pots with ample drainage holes and a prepared soil mix. Utah State describes the ideal soil as moist, well drained and high in organic matter. Our guide on how to make potting soil covers blends.
• Avoid waterlogging. Illinois warns that overwatering can cause root rot.
• Put the pot on wheels or a caddy if it's large. You'll move it at least twice a year.

Sun, heat, water and feeding

Sun and heat

NC State lists lemongrass for full sun, meaning 6 or more hours of direct sun a day. The RHS recommends a warm, sunny, sheltered spot outdoors in summer. A south- or west-facing balcony, often too hot for herbs like cilantro, suits it well.

Water

This is where lemongrass differs from Mediterranean herbs. Utah State stresses that containers must not dry out, and the RHS advises keeping container compost evenly moist and checking it regularly in warm weather. A large plant in summer heat can use water quickly, so check daily during hot spells. A self-watering container can help if you're away often.

Moist doesn't mean soggy, though. Water deeply, let the excess drain, and don't leave the pot standing in a full saucer.

Feeding

Lemongrass is a heavy feeder for an herb, and sources give a range of schedules:

• Utah State: a half-strength balanced soluble fertilizer every 7 to 10 days for outdoor containers.
• Illinois Extension: a general-purpose liquid fertilizer about every two weeks.
• RHS: a general-purpose liquid feed every two or three weeks from spring to late summer, or slow-release fertilizer mixed into the compost when growth starts in spring.

Any of these works. Pick the one that fits your routine, and follow the product label. Our guide to fertilizer for potted plants explains the difference between liquid and slow-release options.

Tip: Wear gloves when handling or harvesting a mature clump. The RHS warns that the leaf blades can be sharp.

Harvesting the stalks

Utah State says you can harvest once stalks reach 1/2 inch (1.3 cm) thick, at any time during the season. In short-season areas, the main harvest often comes just before the first fall frost, after the plant has had all summer to bulk up.

How to harvest:

1. Take stalks from the outside of the clump, as the RHS recommends. Utah State suggests harvesting older stalks first to encourage new growth.
2. Cut at ground level with a sharp knife, or twist and pull an outer stalk free.
3. Trim it down. The RHS says the lower 4 inches (10 cm) of each stem has the best flavor. Strip off the tough outer layers and leaves, as both Utah State and UF/IFAS Gardening Solutions describe.
4. Store extras. Utah State notes that stalks can be frozen for up to 6 months.

The RHS gives a harvest window of May to September in the UK. In warmer climates, the season runs longer.

Overwintering lemongrass indoors

If you live outside zones 8b to 11b, this step decides whether you'll have a plant next year. Start well before frost.

Temperature thresholds for moving potted lemongrass indoors.

When to bring it in

The RHS says to bring plants indoors before overnight temperatures fall below 45°F (7°C). Toronto Master Gardeners move it a little earlier, once nights drop to about 50°F (10°C). Either way, watch the forecast from early fall rather than waiting for the first frost warning.

How to prepare it

1. Harvest first. Take any thick stalks you want to use or freeze.
2. Cut the leaves back. The RHS suggests cutting all leaves to 2 to 4 inches (5 to 10 cm) above the base if indoor space is tight. You can also wait and do this in early spring.
3. Check for pests. Utah State lists spider mites as mainly an indoor problem, so rinse the foliage before it comes in.

Where to keep it

Choose a bright spot, kept above 45°F (7°C). The RHS notes that an unheated greenhouse may be too cold. Illinois Extension recommends a very bright spot indoors, such as your sunniest window. A cool room is fine: the plant just needs to survive, not grow fast.

Winter care is the opposite of summer care:

• Water sparingly, as the RHS advises. Let the top of the mix dry before watering again, but don't let the pot dry out completely (NC State warns against this).
• Feed less. Utah State suggests monthly feeding for indoor potted plants; Illinois says to reduce feeding indoors.
• Expect slower growth. Utah State notes that indoor plants produce fewer stalks because of low light.

For more on keeping herbs going on a windowsill, see our guide to growing herbs indoors year-round.

Watch out: NC State Extension lists lemongrass as a problem for cats, dogs and horses. Keep an indoor pot out of pets' reach.

A backup plan

Utah State describes a space-saving option: before or at the first fall frost, save a 6 inch (15 cm) section of the bulbous base with roots attached, pot it up, and grow it on in a warm, bright, sunny spot. A few small rooted pieces take up far less room than a whole clump.

Dividing a crowded clump

A potted lemongrass clump fills its container within a season or two. Utah State notes that dividing older plants improves productivity, and the RHS recommends dividing established clumps in spring.

1. Water the pot the day before, then tip the clump out.
2. Split it into two or more sections with a spade, saw or sharp knife. Each section should have good roots and several strong stems, per the RHS.
3. Repot the best section in fresh mix, and pot up or give away the rest.
4. Trim the leaves back to reduce stress while the roots settle.
5. Keep it warm and evenly moist until new growth shows.

Spring division fits neatly with the winter routine: the plant comes out from indoors, gets split, and the healthiest piece goes back outside once nights are warm.

Frequently asked questions

Can lemongrass stay in a pot year-round?

Yes. Lemongrass grows well in containers as long as the pot is big enough and the plant is divided when it gets crowded. NC State lists it for container growing and suggests overwintering it as a container plant without letting it dry out.

Why is my potted lemongrass turning brown?

Common causes are a pot that dried out, cold damage, or normal aging of outer leaves. UF/IFAS notes that the leaves can turn scarlet or dark red in fall and winter. Utah State also lists leaf blight, which shows as reddish-brown spots on leaf tips and margins; remove affected leaves.

How long does lemongrass take to grow from a grocery stalk?

Roots appear in about 2 weeks in water, according to Utah State. Growth stays slow until summer heat arrives, and Utah State says plants typically produce several harvestable stalks by late summer.

Can you grow lemongrass indoors all year?

You can keep it alive indoors, but it won't be very productive. Utah State notes that indoor plants produce fewer stalks due to low light. A summer outdoors in full sun gives a much bigger harvest.

Is growing lemongrass in pots better than in the ground?

In zones colder than 8b, a pot is the easiest way to keep a plant from year to year, because you can bring it in. In warm zones, the ground gives a bigger clump with less watering, but a pot keeps its spread in check on a patio or balcony.