Known for its delicious lemony taste and scent, lemongrass (often spelled as lemon grass) is a great double-duty plant that is perfect for adding to your herb garden. Having your own plant puts fresh herbs at your fingertips for your favorite Asian dishes and makes a beautiful ornamental plant, whether grown inside or outside in the garden.
Lemongrass is common in Asian cuisine, primarily used to flavor Thai and Vietnamese dishes. It has a bright, citrus taste without the bitterness of lemon peel, making it a great replacement. The leaves also contain citronella oil that acts as natural whitefly and mosquito repellent and citral, which is used as a fragrance.
Plants grow as a tall, grassy clump maxing out at 3 to 5 feet in height. Multiple stalks emerge from the same base to create a dense grouping, and the blades arch or droop over as they grow tall. While plants don’t grow in as tight of a group as some grasses, lemongrass is often grown as an ornamental grass or privacy screen.
There are fifty-five different Cymmbopogon species, but two are interchangeably known as lemongrass: West Indian lemongrass (Cymbopogon citratus) and East Indian lemongrass (Cymbopogon flexuosus). The two types are suitable for culinary use, but they have slight differences in flavor and their growing habits.
- Malaysian origin.
- More commonly used as a culinary herb.
- Strong citrus flavor.
- Shorter in stature; grows to about 3’ tall.
- Typically propagated via cuttings or divisions.
East Indian lemongrass
- Native to India, Sri Lanka, Burma, and Thailand.
- Less commonly grown cultivar.
- Less flavorful.
- Deep purple stem bases.
- Taller in size; grows between 4 and 5 feet tall.
- Resistant to rust disease.
- Reproduces prolifically through seeds.
- Can become invasive.
As both of the common cultivars are native to Asia, lemongrass plants prefer sunny, hot growing conditions. In warm climates(USDA plant hardiness zones 10 and 11), lemongrass grows as an outdoor perennial. In cold climates with freezing temperatures, overwinter lemongrass indoors near a sunny window: dig up a few stalks, trim them down, and plant in small pots.
When growing your own lemongrass, you have four different options for plants. You can start via seeds (either indoors or direct sowing), you can propagate new plants through cuttings, you can divide mature clumps, or you can buy a young plant from an online retailer (or a local nursery if they have plants available).
Cuttings are the preferred propagation method, especially for the West Indian cultivar. East Indian lemongrass is usually started from seed.
Starting plants from seeds isn’t as successful as other propagation methods. The seeds need warm temperatures and high humidity levels for germination. These conditions increase the chances of fungal problems and damping off, which can quickly kill most if not all of the new sprouts. After sowing seeds, plants should be harvestable in 75 to 100 days.
- Fill container(s) to just below the top of the pot with premoistened potting soil or seed starting mix.
- Gently tamp down the soil to get rid of unintentional air pockets.
- Place a handful of seeds about 6-inches apart and about one-quarter inch deep.
- Place the container(s) where the temperature is at least 70°F.
- Keep the soil surface moist by misting the containers with a spray bottle.
The preferred—and easy—method for starting new plants is accomplished by propagating stem cuttings. Take cuttings from a mature plant, or you can root intact lemongrass stalks from the grocery store. Unlike other plants that need soil, stalks can be set in water to get roots started and then transplanted into containers or the ground.
- Remove the lower leaves from the stalk to expose the bulb.
- Place the stalk in a glass or jar of water.
- Change the water every day, so it doesn’t become stagnant or harbor bacterial growth.
- Once roots form, plants can be transplanted outdoors when they are at least an inch long.
It’s best to divide your lemongrass clumps in the spring, just after the temperatures begin to climb. You want the chance of frost to have passed, but active spring growth hasn’t kicked in yet. Dividing them when they are still dormant minimizes how much shock the plants experience, and they will take off growing once the weather warms.
- Water the soil well to loosen the ground.
- Using sharp scissors or hedge shears, cut the tops of the plants off just above the spot where the stem thickens.
- Carefully dig around the entire base of the plant (or remove from the container), trying to avoid cutting through the roots.
- Lift the plant up and pull it out of the ground, laying it down on a tarp.
- Loosen soil from the roots using your fingers.
- Divide the plant into sections using your hands to break it apart or a shovel or hori hori knife to cut through the root ball. Make sure each section has several roots attached that are at least one inch long.
- Replant each section back into the ground or into containers.
Plants are susceptible to frost and cold temperatures, so it is critical to wait to plant them outdoors until the threat of the last frost has passed in spring and temperatures are above 40°F. Divide mature plants at the same time too. If you are starting seeds or cuttings indoors, get them going a month ahead of time.
Garden plants prefer rich, loamy soil that is slightly acidic or close to neutral. Before planting, mix a couple of inches of finished compost or fully decomposed manure into the garden bed. If planting in a container, choose a high-quality potting mix or coconut coir for the growing substrate. Both have excellent water retention yet allow excess water to drain quickly.
A week before it’s time to transplant your indoor seedlings, start moving them outdoors, gradually increasing the time they are outside to harden them off. Start with a couple of hours during the day, bringing them in at night. Every day, give them more time outside so they acclimate to the different temperature and sunlight exposure.
If you are direct sowing seeds, space them 6-inches apart within the row, with two feet between the rows. After about a month, you can thin the seedlings when they are a few inches tall, so they are twenty-four inches apart. When transplanting seedlings, plant them at the final, 24-inch spacing for mature plants.
When it comes time to plant, start by digging holes about twice as wide as the seedling’s root ball and slightly deeper. Set the plantlet in the holes so the bulb’s base is about an inch before the soil surface. Fan the roots out gently to encourage spreading and gently backfill the hole, tamping out air pockets as you go.
Plants grow best in full sun conditions but will tolerate a little shade. They need a minimum of 6 to 8 hours of direct sunlight daily. If you are growing them in containers inside, they need a sunny spot that gets at least 8 hours of sun; a south-facing window is preferable. If necessary, supplement them with indoor growing lights.
Lemongrass plants need plenty of water but do not like their roots to be soggy. Allow the top inch of the growing substrate (whether it be potting soil in a container or the garden soil) to dry out before watering. Outdoor plants usually need water once or twice a week. Container plants need to be watered about every other day.
Due to its rapid vegetative growth, lemongrass is considered a heavy feeder and needs frequent fertilization to replenish nutrients depleted from the soil. Give plants a dose of water-soluble high-nitrogen plant food once or twice a month when the plants are actively growing, or add compost to the top of the soil to provide new nitrogen.
When plants are young, pull any weeds by hand that pop up around them to minimize competition. After plants become established, they typically outcompete weeds, so there is little need for you to pull weeds as they grow. Container plants will have little or no trouble with weeds if the growing media is free of weed seeds.
Pruning lemongrass plants is pretty simple. In the fall, when you’re cleaning up the garden, do not cut back the leaves. They will naturally die back in the winter, insulating the base. When plants are still dormant at the end of the winter, cut the stems to about 6-inches high. When the weather warms, the plants quickly send up new shoots.
Citral is a naturally occurring compound found in plants that works as a pest repellent, so lemongrass has few insect pests. Growing plants indoors, you may see problems with spider mites when overwintering or fungus grants if overwatering. Both insects are treatable by spraying the plant with neem oil or insecticidal soap.
West Indian plants are also susceptible to rust fungus. This fungal disease results in brown spots or streaks on the leaves, ultimately causing plant death. To prevent rust, water the soil around the base of plants, keeping water off of the leaves.
You can harvest lemongrass when plants are more than twelve inches tall and at least a half-inch wide at their base. Once they are mature enough, harvest material frequently to encourage new growth. The edible portion of the plant is near the bottom of the stalk, so when harvesting, you want to remove the entire swollen base.
- Plants continuously send out offshoots as they grow, leading to a very dense rootball. Every couple of years, you need to break up this mass and divide plants to prevent overcrowding.
- If you grow lemongrass indoors and have pets, be careful since it is considered toxic to dogs and cats.
- Lemongrass tends to spread, and it can quickly take over an area in your garden if left to its own devices. Growing it in one or two-gallon containers helps keep it contained.
- In arid areas, or when growing plants indoors, mist the leaves periodically to increase the moisture level around the plant.