Prized for its baby blue flowers and bright-green leaves, plumbago (Plumbago auriculata) is an evergreen shrub species widely cultivated within U.S. Department of Agriculture plant hardiness zones 8b to 11. It is a carefree, drought-tolerant shrub that suffers few problems if grown under warm, sunny conditions. Plumbago propagates easily from seeds, cuttings and offset divisions, which all perform best when started in summer. However, specific plumbago cultivars such as Royal Cape (Plumbago auriculata "Royal Cape") must be propagated vegetatively to ensure the resulting plants possess the same characteristics as the parent.
Start plumbago seeds in early summer when the days are long and warm. Fill a 4-inch plastic pot with clean, peat-based soil or compost for each plumbago seed. Moisten the soil thoroughly before sowing the seeds.
Sow one plumbago seed in each pot at a depth of 1/4-inch. Cover the seed completely with soil so it is not exposed to air and light. Mist the soil with water, then firm it to increase contact with the seed.
Set the pot in a bright, sheltered location such as indoors near an east-facing window or outdoors under a south-facing porch. Cover the pots with a propagation dome. Warm the seeds to 70 degrees Fahrenheit using a heating mat if daytime temperature stay below 65 degrees.
Maintain constant, light moisture in the top 1-inch of soil during the germination process, but let the surface dry out between waterings to prevent mold. Water with a spray or misting bottle to keep from dislodging the plumbago seeds.
Watch for germination in roughly 25 days, or three to four weeks. Uncover the plumbago seedlings once they emerge and continue to water whenever the soil-surface dries out and remove the heating mat.
Grow the plumbago seedlings in a very bright, wind-sheltered location until early autumn, then acclimate them to direct sun. Transplant them into the ground in spring or autumn of the following year.
Take a 2- to 6-inch cutting from the end of a healthy, non-blooming plumbago stem. Snip it just beneath a set of leaves. Remove the bottom two sets of leaves to expose the growth nodes.
Pot the plumbago cutting in a 4-inch plastic pot filled with clean, moist soil. Make sure both sets of exposed growth nodes are below the soil-surface. Firm the soil against the stem.
Cover the pot with a plastic bag, which will help hold moisture around the plumbago cutting. Set the pot on an east-facing windowsill or outdoors in a bright, sheltered location. Shield it from direct sunlight.
Moisten the soil if it dries out in the top 1 inch and mist the plumbago cutting every few days to keep the foliage hydrated. Lift the plastic bag for an hour or so if excess condensation forms inside.
Check for roots in four to six weeks by gently tugging or pulling on the base of the plumbago stem; if it feels firmly stuck to the soil, it has rooted. Remove the plastic bag after rooting and continue to mist the cutting for another week.
Transplant the plumbago into a permanent bed in autumn. Choose a sunny planting site, or one with light afternoon shade in inland areas with hot, dry summers.
Divide plumbago in autumn after the flowers have faded and the weather has cooled slightly. Water the parent plant to a 4-inch depth the night before dividing it to soften the soil and hydrate the roots.
Measure out 3 inches around the plumbago and dig down around the root ball using a spade or shovel. Lift the plant with its root ball intact and move it to a shady location to work.
Cut the plumbago into divisions, each with an equal amount of roots and at least three to five stems per division. Discard the center of the plant if it appears woody or sparse of foliage.
Transplant the plumbago divisions into a prepared bed with the same soil and light conditions as the parent plant. Space them 3 feet apart. Spread a 2-inch layer of mulch between them to help keep the soil moist while they root.
Things You Will Need
- 4-inch plastic pot
- Peat-based soil
- Propagation dome
- Heating mat
- Spray bottle
- Plastic bag
- Always use pots with multiple drainage holes.
- Floridata: Plumbago Auriculata
- University of Florida IFAS Extension: Plumbago Auriculata
- Washington State University Extension: Propagating Plants from Seeds
- University of California Cooperative Extension: Plant Propagation-Your Can Do It!
- Virginia Cooperative Extension: Propagation by Cuttings, Layering and Division
- American Horticultural Society Plant Propagation: The Fully Illustrated Plant-by-Plant Manual of Practical Techniques; Alan Toogood
- Medioimages/Photodisc/Photodisc/Getty Images