Lemongrass is best planted from potted nursery starts in spring, after all danger of frost has passed. Be aware that this plant contains cyanogenic glycosides and other oils that are mildly toxic to dogs, cats, and horses. Lemongrass is fragrant and also known as a pest repellent. The smell of the plant’s oil seems to deter unwanted insects, such as mosquitos.
Light
Lemongrass grows best in full sun, even in hot climates. At least six hours of direct sun per day will meet the plants’ energy needs. Plants growing in shade will be sparse and may attract pests.
Soil
Lemongrass plants prefer rich, loamy soil. You can create this ideal soil by adding several different soil amendments: compost, manure, and leaf mold are all enrichments you can add at planting time.
Water
Lemongrass prefers moist soil for best plant growth. The standard “1 inch per week” favored by many garden plants will allow lemongrass to thrive, but it can get by on considerably less. Once established, it has a good tolerance for drought. A 3-inch layer of mulch can help conserve soil moisture and will enrich the soil as it breaks down.
Temperature and Humidity
Lemongrass thrives in hot, steamy climates. The time for growing lemongrass outdoors is similar to the timing for tomato planting—when night temperatures are in the 50s, it’s time to plant. Lemongrass is very frost sensitive, so if you plan to overwinter the plant indoors in pots, bring it inside before temperatures drop into the 40s.
Fertilizer
As a grassy plant, lemongrass needs a nitrogen-rich fertilizer for its best growth. You can use a slow-release 6-4-0 fertilizer that will feed throughout the growing season. You can also water with manure tea, which will add trace nutrients.
Types of Lemongrass
There are no named cultivars of lemongrass, but another species in the Cymbopogon genus is worth not—Cymbopogon nardus, also known as citronella grass. This plant is not edible, but it has a pungent but pleasant odor that can be effective as an insect deterrent when grown in pots on patios or decks.
Pruning
Lemongrass plants that live for more than one season benefit from an annual haircut to tidy up plants and remove dead foliage. The plant will naturally die back for the winter, when you should leave the browning leaves alone to protect it from frost. Shear the ornamental grass to about 6 inches high at the end of winter, when plants are in their resting phase. Lemongrass plants will rebound quickly and send up new shoots when warm weather returns.
Propagating Lemongrass
Lemongrass grows in clumps that make it very easy to propagate by division. Here’s how:
How to Grow Lemongrass From Seed
Lemongrass is also easy to start from seed, though it can be hard to find the seeds offered for sale. Even online retailers usually ship small living plants. But if you do find seeds, they are easy to germinate in warm, moist soil. Press the seeds lightly into a sterile potting mix, and keep moist until germination, which occurs usually within about 10 to 14 days. When plants are about 3 inches tall, thin them to a foot apart. Keep indoor pots in a sunny spot.
Potting and Repotting Lemongrass
Choose a large container for growing your lemongrass, at least 12 inches in diameter. This is both to accommodate a healthy root system and to prevent top-heavy plants from tipping over. In cold climates, you can grow a single root division in a small container in a sunny windowsill to keep the plant going for next season’s harvest. Use high-quality commercial potting soil for potting up a lemongrass plant. Choosing a potting soil premixed with a time-released fertilizer can save you an extra step in feeding your plants. If your lemongrass plant grows in the same container year after year, it’s best to repot in the spring to replenish the soil.
Overwintering
In regions where lemongrass is perennial (zones 10 and 11) it often remains evergreen year-round. Gardeners in zones 8 and 9 may find that it dies back to the ground in winter, then returns the following spring. In colder regions, it’s possible to dig up clumps and plant them in containers to grow indoors in a bright, sunny location for the winter.
Common Plant Diseases
In some areas, rust fungus can affect lemongrass plants. Symptoms include brown spots or streaks on leaves, leading to plant death. Prevent rust by watering plants at the soil level, not from above the leaves.
Common Problems With Lemongrass
The most common complaint with lemongrass is that it easily dries out, especially when grown in pots indoors. While outdoor garden plants can be fairly drought-tolerant when well established, this is not the case with potted plants, especially in dry indoor winter conditions. Water your potted lemongrass plants regularly to keep them alive.
