🌿 When to Plant Lemongrass

Lemongrass is a tropical clumping grass grown for the tender, citrus-scented base of its stalks, essential for Thai and Vietnamese cooking. It’s hardy as a perennial only in USDA zones 9-11; everywhere colder, gardeners grow it as a warm-season annual or overwinter a potted clump indoors. Give it a full season of heat and sun and a single stalk can multiply into a dense clump three to five feet tall by fall.

Choosing a Lemongrass Variety

Most lemongrass sold for planting, whether as bare stalks at an Asian grocery store or as nursery starts, is West Indian lemongrass (Cymbopogon citratus), the mild, sweet-lemon type used in cooking. It rarely flowers in cultivation, so it’s propagated by dividing the clump or rooting stalks rather than by named cultivars. If you come across East Indian lemongrass (Cymbopogon flexuosus), know that it’s grown mainly for essential oil and has a sharper, less citrusy flavor; it isn’t the type you want for the kitchen. Citronella grass (Cymbopogon nardus) is a related but different ornamental species grown for mosquito-repellent oil, not for eating, and it grows larger and coarser than culinary lemongrass.

To start your own plant, buy fresh stalks with the root end intact, set them root-down in a jar with an inch of water on a sunny windowsill, and change the water every couple of days. Roots usually appear within one to three weeks; wait until they’re an inch or two long before potting up or planting out.

Spacing, Sun, and Soil

Lemongrass wants full sun, six or more hours a day, and rich, well-drained soil; it sulks in heavy clay that stays wet. Space clumps 24 to 36 inches apart, since a single plant can spread two to three feet wide by the end of the season, and keep it away from walkways since the leaf edges are sharp enough to nick skin. In-ground beds benefit from a couple inches of compost worked in at planting time. In containers, use a large pot, at least five gallons, with a standard well-drained potting mix, since a mature clump builds a substantial root mass.

Watering

Keep the soil consistently moist through the growing season, especially in the first few weeks after transplanting, when the shallow new roots dry out quickly. Once established, lemongrass tolerates brief dry spells but grows fastest and stays most tender with steady moisture, about an inch of water a week and more in containers or during heat waves. Ease off watering in fall as growth slows, and if you’re overwintering a potted clump indoors, let the top inch of soil dry between waterings since the plant is semi-dormant in low light.

Top Growing Tips

• Root stalks from an Asian grocery store in a glass of water rather than starting from seed; seed-grown lemongrass is slower and less reliable than division or rooted stalks.
• Wait for consistently warm weather, with nights staying above 50°F, before transplanting outdoors. A late cold snap will stunt or kill young plants.
• Mulch around the base in summer to conserve moisture and suppress weeds while the clump fills in.
• Wear gloves when handling mature plants. The leaf blades have a fine serrated edge that can slice skin.
• In zone 8b and colder, either treat lemongrass as an annual or dig and pot a clump before first frost to overwinter indoors near a bright window.

Common Problems

Lemongrass is fairly pest-resistant; its citronella oil deters many insects, but a few issues still show up.

• Rust: orange-brown pustules on the leaf blades, favored by humid, still air. Thin crowded clumps for airflow and water at the base instead of overhead.
• Spider mites: most common on plants overwintered indoors in dry, heated air. Fine webbing and stippled leaves are the giveaway; raise humidity and rinse foliage occasionally.
• Slow or stunted growth: usually a sun or temperature problem rather than disease. A cool or partly shaded spot keeps the clump small all season.
• Root rot: from soil that stays waterlogged, especially in containers without drainage holes. Let the soil surface dry slightly between waterings.

Companion Planting

Good companions: tomatoes, peppers (its scent can help mask them from some pests), cabbage-family crops. It’s also a popular companion near patios and entryways since its citronella content helps repel mosquitoes.

Avoid planting near: nothing in particular is harmed by lemongrass, but its size and dense root mass make it a poor neighbor for small, shallow-rooted plants that need the space it will eventually claim. Give it its own bed or a large container rather than tucking it into a tight herb border.

Harvest Timeline

Begin light harvesting once stalks reach pencil thickness at the base, usually 100 to 120 days after transplanting or rooting a stalk, though this depends heavily on heat and day length. Cut individual stalks at the base with a sharp knife rather than pulling, which can damage the clump, and take the outer, older stalks first so the center keeps producing. For the mildest flavor, use the lower four to six inches of the stalk, the tender white-to-pale-green core, and save the tougher upper leaves for steeping in teas or broths. In zones where lemongrass overwinters, established clumps produce more heavily in their second and third years as the root mass expands.