Lemongrass (Cymbopogon citratus) is a popular perennial grass valued for its distinct lemon aroma and ornamental appeal. While many gardeners propagate this tropical plant using stem cuttings, starting lemongrass from seed is a viable method for cultivation. This process requires patience and specific environmental controls, as seed germination differs from rooting a cutting.
Preparing the Environment and Supplies
Since lemongrass originates in tropical climates, successful germination requires starting seeds indoors well before the last expected frost date. Begin the process approximately four to six weeks prior to when outdoor temperatures stabilize above 50°F (10°C). Lemongrass seeds require consistent warmth during the initial stages of growth.
The planting medium should be a light, sterile, and well-draining seed-starting mix. Avoid heavy garden soil, which can impede root development and retain too much moisture. Containers should be shallow flats or small cell packs with adequate drainage holes to prevent waterlogging. Cleaning containers before use minimizes the risk of fungal diseases affecting young seedlings.
Securing high-quality, viable seeds is recommended, as lemongrass seed viability can sometimes be lower compared to other common garden vegetables. Before sowing, moisten the seed-starting mix thoroughly until it is damp, but not saturated. This pre-moistening prepares the environment for the seeds.
Sowing the Lemongrass Seeds
Lemongrass seeds are tiny and require light for successful germination, making surface-sowing the appropriate technique. Gently scatter the seeds across the surface of the pre-moistened mix, aiming for even distribution. Overcrowding leads to competition for resources and increases the likelihood of damping-off disease.
The seeds should not be buried deeply after scattering. Cover them with only a fine dusting of vermiculite or a light sprinkle of the seed mix. This minimal covering maintains contact with the soil while allowing sufficient light to penetrate. Immediately after sowing, lightly mist the surface with water using a spray bottle to settle the seeds without displacement.
To maintain high humidity and temperature, cover the planting tray with a clear plastic dome or plastic wrap. Place the covered tray in a location that receives bright, indirect light.
Caring for Seedlings Until Establishment
Maintaining warmth is necessary for triggering germination, with ideal temperatures ranging between 70°F and 85°F (21°C to 29°C). Many gardeners use a heat mat beneath the trays to ensure consistent bottom heat, which improves germination rates and speed. The plastic dome traps moisture, creating a miniature greenhouse effect.
Under optimal conditions, the grass-like seedlings typically emerge within 10 to 20 days after sowing. As soon as the first sprouts appear, remove the plastic dome or wrap to allow for better air circulation and prevent fungal growth. Immediately transition the newly germinated seedlings to a strong light source.
If natural sunlight is limited, provide 12 to 16 hours of supplemental light daily using a fluorescent or LED grow light. Position the grow lights just a few inches above the seedlings to prevent them from stretching (etiolation). Insufficient light at this stage leads to weak stems that struggle to support the developing plant.
Watering requires careful management to keep the soil consistently moist but never soggy. Overwatering saturates the soil, displacing oxygen and making roots susceptible to rot and diseases like damping off. Watering from the bottom allows the soil to wick up moisture without disturbing the young plants.
Transplanting Established Lemongrass
Seedlings are ready for transplanting when they reach four to six inches in height and have developed several true leaves. Before moving them permanently outdoors, the young plants must undergo a gradual process called “hardening off.” This step prepares them for the harsher outdoor environment, including stronger sunlight, wind, and fluctuating temperatures.
Begin hardening off approximately one week before the final planting date. Place the seedlings outdoors in a sheltered, shady spot for just a few hours each day. Gradually increase the duration of outdoor exposure and the intensity of light over the week. This acclimatization prevents shock and leaf burn when they are moved to their permanent location.
Lemongrass thrives in a location that receives full sun (at least six to eight hours of direct sunlight daily). If planting directly into the ground, space the plants 18 to 24 inches apart to allow for mature clump size and rhizome expansion. When potting, choose a large container, at least 12 inches in diameter, to accommodate the plant’s rapid growth once established.