Lemongrass is a tall, fountain-like tropical grass whose thick stalks smell of lemon and are a staple of Thai and Vietnamese cooking. In warm climates it becomes a handsome clump several feet across; in cold ones it is still worth growing as a summer annual or in a pot.
Use the tender lower stalks in curries, soups and teas, and the leaves for a fragrant infusion. A single clump produces far more stalks than one kitchen needs, so it is a generous plant to share with neighbours. This crop is in the Poaceae family, needs full sun, and takes 90–120 days to reach maturity, so it pays to know what it wants before you sow. This guide covers it all: starting seeds, transplanting, soil and feeding, watering, sunlight, pests, companion plants, harvesting and the problems most likely to catch you out. When you bring a pot indoors for winter, cut the leaves back to about 6 inches so the plant is manageable, keep it in the brightest spot you have, and water sparingly until spring.
Lemongrass at a glance
| Growing factor | What lemongrass need |
|---|---|
| Sun | full sun |
| Soil pH | 6.0–7.0 |
| Days to germination | 10–21 |
| Days to maturity | 90–120 |
| Spacing | 24–36 inches |
| Water needs | moderate |
| Cold tolerance | tender |
| Family | Poaceae |
Starting seeds
Lemongrass are started indoors and moved outside as seedlings. Sow in trays or cells, keep the mix moist but not wet, and expect germination in 10–21 days. Give seedlings strong light from the moment they emerge — a grow light a few inches above the leaves is worth having.
Start seed early enough that seedlings are sturdy by planting-out time, but not so early that they go leggy indoors. Work backwards from your last frost using our seed-starting calculator, and confirm the timing with your local extension service — Zones 11–13 are frost-free, so the calendar there is about heat and rain rather than frost.
Seed takes 10–21 days to germinate and needs warmth throughout. Dividing an established clump in spring is faster and more reliable than seed — keep a chunk with roots and several shoots and replant it straight away.
Transplanting and planting out
Set young plants out once the soil is workable, or after the last frost where the plant is tender. Handle the root ball gently, plant at the same depth as in the pot, and water in well.
Space plants 24–36 inches apart — crowding is one of the commonest causes of small harvests. Our plant-spacing calculator works out how many plants fit your bed. Harden seedlings off for a week before planting out, and plant on a cloudy day or in the evening so they do not wilt in their first hours outdoors.
Soil and feeding
Herbs mostly want lean, free-draining soil rather than rich ground — too much fertiliser makes soft, leggy growth with weak flavour. Dig in a little compost for structure and make sure water drains away freely, especially in winter.
Aim for a soil pH of 6.0–7.0 — a simple soil test will tell you where you stand. Feed lightly and steadily rather than in one heavy dose: too much fast nitrogen late in the season pushes leafy growth at the expense of the part you eat. Our fertiliser calculator works out amounts for your bed size, and the raised-bed soil calculator tells you how much mix a new bed needs.
Watering
Water needs are moderate: keep the soil evenly moist, watering deeply when the top inch or two dries out. Deep, infrequent watering builds deeper roots than a daily sprinkle.
Herbs in pots dry out faster than herbs in the ground, so check pots daily in hot weather. In the ground, most herbs are happy with a deep watering when the soil dries out rather than a daily sprinkle.
Water at the base of the plant, in the morning, so the leaves dry quickly. Our watering calculator gives a starting point for your bed size, and the watering schedule generator can build a routine around it.
Sunlight and temperature
Give herbs the sunniest spot you have — a south-facing bed, or a pot on a sunny step. Full sun keeps growth compact and flavour concentrated; in shade, most herbs grow leggy and taste weak.
This crop is rated tender for cold tolerance, so plan your season around that: hardy crops can be sown and harvested around frosts, while tender crops need warm soil and frost-free nights. Our sunlight calculator can check whether your spot gets enough sun, and the hardiness-zone finder will confirm your zone.
Pests and diseases
Lemongrass are not especially pest-prone when healthy and well placed, but a few pests turn up regularly. The ones listed for this crop in the growing data are aphids, slugs, cutworms.
- Aphids — Small sap-sucking insects that cluster on soft new shoots, weakening growth. A strong jet of water dislodges them, and ladybirds usually keep them in check.
- Slugs — Slugs feed at night, chewing holes in leaves and fruit — especially young seedlings and berries at ground level. Hand-pick them after dark and keep the ground clear of hiding places.
- Cutworms — Caterpillars that feed at night and cut young stems off at soil level. A cardboard collar around the stem at planting time stops them.
Inspect plants weekly, especially the undersides of leaves, and act early. If you need help identifying what you are seeing, our pest-identifier helper and plant-disease checker walk through the symptoms.
Companion plants
Companion planting puts together plants that help each other — sharing space well, attracting pollinators, or confusing pests. The companions listed for lemongrass in the growing data are a good starting point.
Good companions for lemongrass include:
- Tomatoes
- Peppers
- Marigolds
- Cabbage
Our companion-planting finder can suggest more pairings for your bed plan.
Harvesting
Harvest stalks once they are at least pencil-thick, cutting them at the base with a sharp knife and peeling away the tough outer layers to reach the pale, tender core. Take a few stalks at a time from the outside of the clump so the centre keeps growing.
Expect the crop to be ready about 90–120 days after sowing, though weather and variety shift that window by a week or two either way. Our harvest-date calculator works out your expected harvest date from your sowing date, and the vegetable-yield estimator can estimate how much a bed should produce. Harvest in the morning, using a sharp knife or secateurs rather than tearing, which damages the plant.
Common problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| Frost damage | frost killing a tender tropical grass | grow in a pot and move it indoors before the first frost |
| Wilting in dry spells | uneven watering | water deeply when the top inch or two dries out, and mulch |
| Aphids on the plants | aphids feeding on the crop | inspect weekly and act early — hand-pick, wash off, or use barriers |
Frost damage
Likely cause: frost killing a tender tropical grass. The most common failure is cold: a single frost turns the leaves brown and mushy overnight. The other is a pot-bound clump — after a season or two the centre becomes a dense mat of roots, so divide the clump in spring, keeping a chunk with roots and several shoots, and replant it in fresh mix.
Wilting in dry spells
Likely cause: uneven watering. A dry spell while fruit or flowers are forming costs you the crop. Water deeply when the top inch or two of soil dries out, and mulch to keep moisture even.
Aphids on the plants
Likely cause: aphids feeding on the crop. Small sap-sucking insects that cluster on soft new shoots, weakening growth. A strong jet of water dislodges them, and ladybirds usually keep them in check.
Frequently asked questions
How long do lemongrass take to germinate?
10–21 days, in warm, moist conditions. Cool soil slows germination down, so wait for the soil to warm up and keep the seedbed evenly moist — not wet — until seedlings appear.
What soil pH do lemongrass need?
A soil pH of 6.0–7.0 suits lemongrass best. A simple soil test will tell you where your soil stands, and lime or sulfur can nudge pH up or down over a season.
When can I harvest lemongrass?
About 90–120 days after sowing, though weather and variety shift that by a week or two. For nursery-grown plants the wait is shorter than for seed.
Can I grow lemongrass from a stalk bought at the grocery store?
Yes — choose a fresh, firm stalk with the base intact, trim the top, and stand it in a glass of water in a bright spot. Roots usually appear within a week or two; once they are a few inches long, pot it up in free-draining mix and keep it warm.