Perennial leadwort (Ceratostigma plumbaginoides), also known as hardy plumbago, is a long-blooming, semi-woody perennial from western China that will grow throughout South Carolina. This relatively underused perennial blooms in late summer through fall with ½- to ¾- inch-diameter gentian-blue flowers that resemble those of woodland phlox. Flowers occur in a compact inflorescence or cluster at the ends of branches.
Its habit of growth is low and moderately-fast spreading by rhizomes or underground stems, but it isn’t considered invasive. The foliage is medium green, and leaves are about 1½ inches long. Typically the plant grows to between 6 and 10 inches tall with slender, erect stems that arise from the below ground, branching rhizomes. New leaves may have a reddish tint, and the fall color is a bright bronze-red. Perennial leadwort grows best with moderately moist, but well-drained soil, and over-winters in USDA cold hardiness zones 6 through 9. It will tolerate full-sun to partial-sun growing conditions. In warmer climates, like in South Carolina, it will benefit from afternoon shade, but it may bloom a little less under partial-shade conditions. Leadwort can tolerate clayey to sandy soils, and will become fairly drought tolerant once established.
Uses in the Garden
Leadwort makes an attractive groundcover around rocks or cascading over stone walls, and is a good replacement for evergreen English ivy or vinca. However, leadwort is only semi-evergreen in zone 9, and will be deciduous in colder zones.
Perennial leadwort combines well in the garden with bright yellow-flowered perennials, such as Achillea ‘Coronation Gold’ and Coreopsis ‘Zagreb’ or ‘Early Sunrise’. With its low height, leadwort works well at the front of the perennial bed, and because leadwort’s foliage is late to emerge, it can be interplanted with spring bulbs. As the bulb foliage is dying back in the spring, the leadwort foliage is emerging to replace it. Additionally, perennial leadwort looks great in containers, where branches will spill over the sides.
Division & Propagation
Transplanting and division is best accomplished in the spring just before new growth appears. Space transplants 12 inches apart. Fertilize leadwort with a slow-release 12-6-6 fertilizer lightly in the spring and again in the early summer to promote rapid filling in between transplants. Propagate by 3- to 4- inch stem cuttings taken during the summer.
Perennial leadwort was recognized as the 2006 Georgia Gold Medal Winner for perennials. Its long bloom time of true-blue flowers, drought tolerance, deer resistance and lack of pest or disease problems makes perennial leadwort worth adding to the perennial or mixed border garden.