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.