Blue flowering shrubs are not very common. If you are longing for a touch of cool summer- blooming blue for your landscape, you should consider the Plumbago or leadwort.
After doing a little research to find the particular plumbago suitable for the San Joaquin Valley, I found things to be a bit confusing. Apparently, there are two different genera (taxonomic category just below family) that contain plants with the common name of plumbago. One is Ceratostigma and the other is Plumbago. So, in deciding which plant to purchase I would ignore the name at first and look at the description and planting directions. And then when you go to the nursery be sure you know the scientific name. Since both genera have plants whose common name is plumbago, it can be confusing.
Master Gardeners have published lists of drought tolerant plants that are suitable for our hot, dry climate. Included in that publication (“Shrubs for San Joaquin Valley and Foothill Landscapes”) is Plumbago auriculata (or Plumbago capensis) with a common name of Cape Plumbago. It is a drought tolerant herbaceous perennial that can be up to 6 feet tall and 8-10 feet wide. In some publications it is described as a climber and in others it is described as a shrub. To me this suggests that the gardener can train it to be a shrub or a climber and it has the potential to be either. It requires little water, can tolerate full sun or light shade and thrives in warm climates. It has clusters of blue or white flowers and blooms in the summer. (May-October) The leaves are green and turn red when the temperatures turn colder. If the temperatures get very cold the plumbago may go dormant. Protect it from heavy frost if it is in an exposed area. This plant is a native of South Africa.
There is another plant whose common name is hardy plumbago that can be grown as a ground cover. But it is not a true plumbago, but Ceratostigmata plumbaginoides. It can grow to be about 1 foot tall and can spread to 1½ feet wide. It spreads by rhizomes and so it can become aggressive if you don’t keep an eye on it. It does well in sun or partial shade especially when it is hot. It is also suitable for our San Joaquin Valley landscapes. (Notice that these two plants have different generic names.) This plant is a native of China.
There are eight types plants that go by the common name of plumbago.
Plumbago auriculata (also called Plumbago capensis) is the shrub mentioned above. It grows in zones 8-11 (Visalia and surrounding areas are zone 9). You will find it very common in Southern California in the San Diego area. This shrub can grow to be large (8-10 feet tall and 8-10 feet wide) and can be seen along Akers Avenue south of Tulare St., being grown as a shrub and pruned as a hedge. The flowers are a lighter blue.
Plumbago indica (also P. coccinea and P. rosea) has red flowers. It grows in partial shade in zones 8-11. You will find it along the gulf coast and Florida. The plant is poisonous so I would not recommend it. It is a small shrub that can grow to be about 2 feet tall and 3 feet wide.
Plumbago europaea, as the name implies, can be found in Europe and central Asia. The flowers are a pale blue.
Plumbago pulchella in native to central Mexico. The flowers are star shaped and pale blue to almost white and small. The flowers grow in an alternating pattern along a thin stalk instead of in a cluster at the end of the stalk. Ceretostigmato plumbaginoides is the ground cover I mentioned above. It grows in zones 5-9. The soil needs to be well draining. It will tolerate full sun, but appreciates afternoon shade. The flowers are a deep blue.
Ceretostigmata willmottanium is known as Chinese plumbago and is a smaller shrub. It grows to be about 4 feet tall and 4 feet wide. It grows well in zones 6-9. It prefers a similar habitat with full sun to partial shade and well drained soil. Ceretostigmata griffithii is also called Burmese plumbago. It likes zones 7-10. It is low growing, with a spreading manner. The leaves have purple edges. It likes moist, well-drained soil.
Ceretostigmata minus is grown in China in hot environments. It is deciduous rather than evergreen. It is a small shrub, growing to be about 2 feet tall.
Plant Plumbago in the spring after the possibility of frost has passed. Buy in the nursery as a transplant, or it can be grown from seed or stem or root cuttings. If grown from seed, start it early indoors so the seedling is ready to be set outdoors in the spring. Always wear gloves when handling the plumbago. It produces a toxic chemical that can cause contact dermatitis on your skin if it gets on it. The fruit is poisonous to pets so plant it in an area where pets can’t get to it. You can train the plumbago to climb a trellis or train it to grow as a shrub. Water deeply in well-draining soil about twice a month after they are established.
There are two types of plumbago that could be grown in the San Joaquin Valley. One is a shrub or vine and the other is a ground cover. The plant is easy to maintain once it is estab lished and produces a pretty blue flower for most or all of the summer. It does well in sun or partial shade and is drought tolerant. The fact that it produces a toxic chemical makes me a little hesitant to recommend it to someone with pets. But in an area that pets can’t get to, it would be a lovely addition to the home landscape.
Plumbago is a low-maintenance, deer-resistant, and drought-tolerant plant that should thrive and spread easily once it is established.
The Master Gardeners will be live to answer your questions on Saturday, Feb. 18, 8 to 11 a.m. at Visalia’s Farmer’s Market in Sequoia Mall’s southwest parking lot. You can also contact them at 559-684-3325, or visit their web site at ucanr.edu/sites/UC_Master_Gardeners.
This column is not a news article but the opinion of the writer and does not reflect the views of The Sun-Gazette newspaper.
