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Plumbago—A Gardener’s Dream

November 17, 2008
Martha Proctor

We just returned from a wonderful trip, which included visits to many stellar museums in Florence, Venice, and Rome. I was struck by how often we came across the lovely blue flowers of Plumbago auriculata in both private and public gardens. I recently planted Plumbago in my garden, so was interested in knowing more about this hardy, drought tolerant shrub.

As Plumbago is native to South Africa, it is not surprising that Plumbago is a popular ornamental in Mediterranean gardens where it flourishes nearly all year, especially in warm and relatively frost-free settings. Plumbago is an evergreen shrub which forms a loose, rounded mound three to ten feet high and wide. The long, delicate, semi-woody branches can be trained to cover a trellis, pruned into a more compact mounded shrub, or its long, gracefully arching branches can be left to sprawl. The oblong leaves are green in summer but turn a rich red when the weather turns colder.
For half the year, sky blue to white, snowball-sized clusters of flowers are borne at the ends of vine-like stems. The popular cultivar, 'Royal Cape,' has intense cobalt blue flowers. The white flowered variety (Plumbago auriculata var. alba) is slightly less vigorous but its blooms appear to glow in the dusk. It is best to buy plants in bloom so that you get the color you desire.
The name Plumbago is derived from the two Latin words plumbum, lead, as the plant was thought to be a cure for lead poisoning and ago, a Latin suffix used to indicate a resemblance or property. Auriculata means ear-shaped and refers to the leaf base. Jean-Baptiste Lamarck, a French botanist, named the plant Plumbago auriculata in 1786 in the East Indies where it was cultivated as a garden plant. Eight years later, in 1794, Carl Peter Thunberg, a Swedish botanist, assigned the name Plumbago capensis to specimens of the plant collected in South Africa—it was this latter name that caught on and became commonly used. However, since Plumbago auriculata is the earlier published name, botanical rules indicate Plumbago auriculata is the preferred nomenclature. Common names for the plant include leadwort and skyflower.
Plumbago is a tender perennial which thrives in light, sandy, well-drained, slightly acidic soil. Plumbago survives with little watering once established and is considered to be drought resistant, especially if plenty of compost and mulch are added at planting.  It does best in full sun, but can take considerable shade and stillproduce an abundance of blooms.   An application of fertilizer encourages continuous growth and flowering. As it is fast growing, Plumbago should be pruned heavily every winter to keep it neat and within bounds. Pruning stimulates the plant to flower profusely as it bears flowers on new wood.   Plumbago loses its leaves in winter and is rather late to come back the next spring, so use caution when cultivating the areas where it grew last year.
Plumbago is propagated easily by seed, division, cuttings taken in winter or early spring, or by removing rooted suckers from the mother plant. Sow seed in seedling trays using a good seedling mix. Cover the seeds lightly; do not allow the seedlings to dry out.
Plumbago is a tough beauty making it a perfect candidate for urban plantings. Use Plumbago as an accent plant in borders, shade or rock gardens, foundation plantings, and for creating visual mass in large, out of the way parts of the garden. Many gardeners use Plumbago as a filler plant under and in front of shrubs that have stronger frameworks. Plumbago is used as a container plant in English cottage gardens as it spills over the sides filling the area with fragrant, blue flowers. Plants that compliment Plumbago in the garden include black-eyed Susans, red chrysanthemums, purple coneflower, and asters, to name just a few. As Plumbago is visited by robins and is a larval food plant for the blue butterfly (Cyclyrius pirithous), it makes a nice addition to the habitat garden.
It seems to have no diseases or pests—even deer will not usually nibble on it. Deer will only eat it if stressed for food. The foliage may turn yellow due to manganese deficiency, but applying manganese sulfate cures this problem. Even if frost blackens the leaves or appears to have killed the plant, it usually recovers quickly. Just prune out the damaged growth.
Plumbago is an extremely reliable, resilient plant, which has been popular for home gardens as well as for commercial landscapes for many years. Its lovely blue flowers are found in gardens all over the world and, as I found, the plant is still popular in Europe. Consider adding this beauty to your drought tolerant garden too.

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