Lemongrass is a tropical grass that thrives in summer heat. It is well suited to container growing, and ideal for greenhouse cultivation. It can be grown as a perennial in our climate, but care must be taken to control moisture in the soil over winter, and to provide protection from frost. It is somewhat challenging to grow, but the reward is fresh, strongly aromatic stalks with very minimal carbon footprint. Hopefully these helpful tips will teach you how to grow lemongrass from seed.
Season & Zone
Season: Hot season
Exposure: Full sun
Zone: Not hardy
Sow seeds indoors in late winter (mid-February to early March on the coast). Transplant outdoors only when night time temperatures are steadily above 10°C (50°F).
Press the seeds gently 5mm (1/4″) into pre-moistened, sterilized seed starting mix. Use seedling trays with plastic domes, or containers sealed inside large plastic bags. Use bottom heat from a Seedling Heat Mat to maintain a soil temperature of 21°C (70°F). Keep seed trays or containers in a dark room or cupboard. Seeds should germinate in 5 to 21 days. The trick is to maintain a moist, not wet, environment. Once seedlings appear, remove the dome or plastic bag, and move them into full sun or beneath strong, full spectrum, artificial light.
Harden seedlings off in early summer by gradually exposing them to full sun and cooler temperatures. Transplant individual seedlings into 5 gallon (or larger) containers, and apply high nitrogen organic fertilizer like Alfalfa Meal or Blood Meal at the time of transplanting. Just mix 1/2 cup into the soil before transplanting. Keep the soil relatively moist throughout the growing period, watering at least 2 or 3 times a week – more in hot weather.
At the end of the growing season, once night time temperatures begin to approach 10°C (50°F), cut back your lemongrass plants to 15-20cm (6-8″) tall, reduce watering, and discontinue feeding. Move your plants to a bright, airy spot, protected from frost. Water only enough to keep the soil barely moist to nearly dry. If plants seem congested, consider dividing them into clumps in early spring, and potting them on. Resume watering and feeding once spring growth appears.
Use secateurs to snip whole stalks from the base of the plant as needed. Stalks should be at least 15mm (1/2″) thick before picking. Lemongrass dries well for use as a tea, and whole stalk segments can be bundled and frozen for use in soups and curry paste all winter long.