Crepe myrtle (Lagerstroemia indica) is a popular flowering tree. Growing it from seed offers a chance to cultivate a new, unique plant, though the process is much slower than using cuttings. This method requires patience, as the resulting seedlings may not have the same flower color or growth habit as the parent plant, a characteristic of sexual reproduction. The journey begins indoors in the late winter or early spring to give the new plants a sufficient head start. Success depends on preparing the seeds correctly and providing a stable, controlled environment.
Sourcing and Pre-Treatment of Crepe Myrtle Seeds
Viable seeds can be collected from mature, dried seed pods that appear on the tree in late fall or early winter. Wait until the small, brown, capsule-like pods have completely dried and started to crack open naturally on the plant. Harvest the pods and gently shake the small, winged seeds into a container. Store them in a cool, dry place until you are ready to plant.
For the best germination rates, the seeds must undergo cold stratification, which mimics the natural winter cycle. Place the seeds between two layers of a damp paper towel or mix them with moist sand or vermiculite. Seal this material inside a plastic bag and place it in a refrigerator for a period of three to four weeks. This chilling period helps to break the seeds’ natural dormancy.
Step-by-Step Indoor Sowing
The ideal time for indoor sowing is late winter or very early spring, approximately six to eight weeks before the final expected frost. Use a sterile, fine-textured seed-starting mix, which is formulated to be light, well-draining, and free of pathogens. Fill your seed trays or small pots with this mix, moistening the medium thoroughly before planting.
Sow the pre-treated seeds on the surface of the soil, pressing them lightly into the medium without burying them deeply. Crepe myrtle seeds require light for germination, so a shallow planting depth is sufficient. Cover the seeds only with a thin layer of fine vermiculite or sifted soil. Maintain a high ambient temperature, ideally between 75 and 85°F, often achieved with a seedling heat mat. Cover the trays with a clear plastic dome or plastic wrap to lock in the high humidity required for sprouting.
Essential Care for Emerging Seedlings
Once the first tiny sprouts appear, immediately remove the plastic dome or wrap to prevent fungal growth caused by excess moisture. The seedlings must receive intense light to prevent them from growing tall and spindly. Place the seedlings under a fluorescent or LED grow light source, maintaining a distance of about 6 to 12 inches above the plant canopy. The light should run for approximately 14 to 16 hours a day to simulate the long days of summer.
Watering should be done carefully to keep the soil consistently moist but never waterlogged, which can lead to damping-off disease. As the seedlings develop their second set of leaves, it is time to thin them out if multiple sprouts emerged in a single cell. Use a small, sharp pair of scissors to snip the weakest seedlings at the soil line, leaving only the single, most vigorous plant in each spot. This practice prevents competition for nutrients and light, ensuring the remaining plant develops a strong root system.
Hardening Off and Transplanting
Before moving your young crepe myrtles to the outdoor garden, they must be gradually acclimated to the harsher external conditions, a process known as hardening off. Over a period of seven to ten days, introduce the seedlings to increasing amounts of direct sun, wind, and cooler temperatures. Start by placing the plants in a sheltered, shady location for just a few hours on the first day, progressively extending the time and exposure to brighter light daily.
The final transplanting should only occur once all danger of frost has passed and the nighttime temperatures remain consistently above 50°F. Select a permanent planting location that receives at least six to eight hours of direct sunlight each day, as this is necessary for abundant flowering. Carefully remove the seedling from its container, disturbing the delicate root system as little as possible. Plant it into the prepared garden soil or a larger container. The first year of growth will focus on root establishment, and the young crepe myrtle may not produce flowers until the second or third growing season.