The Cape Plumbago, Plumbago auriculata, is a popular shrub known for its sky-blue blossoms. Propagating new plants from a mature specimen is a straightforward process, allowing gardeners to expand their displays of this vibrant, low-maintenance species. Propagation can be accomplished reliably through either stem cuttings or by sowing seeds.
Preparing and Taking Stem Cuttings
Propagating Plumbago through cuttings is the most direct method for cloning the parent plant. Take cuttings during late spring or early summer when the plant is actively growing. Select non-flowering, semi-hardwood stems that are firm but still flexible, indicating ideal maturity for rooting.
Use a sharp, sterilized blade to take 3- to 4-inch sections, cutting just below a leaf node. This node is where growth hormones are concentrated, providing the best chance for root development. Remove all but the top two or three leaves to reduce moisture loss.
Dip the cut end into a rooting hormone powder or gel to stimulate new roots, which significantly increases success. Plant the prepared stems into a sterile, well-draining medium, such as a 50/50 mix of perlite and peat moss.
Place the cuttings in a bright location protected from direct sunlight. Cover the pots with a clear plastic dome or bag to create the high humidity necessary for root formation. Consistently moist soil encourages the cutting to generate a new root system.
Starting Plumbago from Seed
Growing Plumbago from seed is slower than cuttings but is a viable option, especially for acquiring new varieties. Seeds can be harvested from dry capsules or purchased. The seeds have a hard outer coat that enforces dormancy, which must be broken to initiate germination.
To overcome this barrier, the seeds require scarification, which involves physically weakening the seed coat. Gently rub the seeds with fine-grit sandpaper or nick them with a sharp blade. Following scarification, soak the seeds in warm water for 12 to 24 hours.
Sow the treated seeds in a seed-starting mix and cover them lightly, about an eighth of an inch deep. Place the trays in a warm environment, maintaining a soil temperature between 70°F and 75°F. Consistent moisture is necessary, but avoid saturation to prevent fungal issues.
Caring for New Plantlings
Once cuttings have developed a robust root system or seeds have germinated, they enter a transitional phase. Cuttings show resistance when gently tugged, typically after four to eight weeks. Seedlings are ready once they develop their first set of true leaves, appearing after the initial cotyledon leaves.
The young plants require a gradual introduction to less humid conditions and stronger light. Remove the plastic cover for increasing periods each day, allowing them to acclimate to ambient air. Once established in individual pots, begin feeding them with a half-strength, balanced liquid fertilizer.
Before planting outdoors, the young Plumbago must be “hardened off.” This involves moving the potted plants to a sheltered outdoor location for a few hours daily, gradually increasing exposure to sunlight and wind over one to two weeks. This slow acclimation minimizes transplant shock.