Dorothy is a Master Gardener, former newspaper reporter, and the author of several books. Michael is a landscape/nature photographer in NM.
Ceanothus Arboreus California Lilac
Various Forms and Colors of Ceanothus
The California lilac (ceanothus) provides fragrant blooms from late spring into early summer, and it comes in several forms for inclusion in your landscape. These upright, evergreen bushes can grow almost 10 feet tall, but there are some that are compact and low-growing groundcovers, which rarely reach over about six inches tall. Most of the flowers are in clusters of deep blue, situated at the end of the stems. But some of the forms have flowers that are a lighter blue, lavender, or white.
Most plants have to rely on the addition of nitrogen to the soil in order to be able to use it, but the California lilac is a nitrogen-fixing plant, drawing nitrogen from the air and storing it in its roots. Not only will you be improving the soil and the health of surrounding plants, you will also be providing a welcome and much-needed habitat for native birds and insects by planting California lilac.
The Ceanothus Ray Hartman
The tree-size California lilacs that have vibrant blue blooms include Ceanothus Ray Hartman and Ceanothus delileanus Gloire de Versailles, although the Ray Hartman, which is a hybrid of two parent species, Ceanothus arboreus, and Ceanothus griseus, seems to be a favorite for people who have a large growing area and are wanting to add a colorful tree to their landscape because it grows to be much taller than the other.
This tree, which grows up to about 20 feet or more, is especially popular in San Francisco with its light to medium blue six-inch flower spikes and is one of the few native trees planted in sidewalk cuts on the street. The leaves of the tree are dark green and glossy, adding to the visual appeal of the tree, which can grow up to about 10-15 feet in only 18 months.
Ceanothus delileanus Gloire de Versailles
The Ceanothus delileanus Gloire de Versailles is a deciduous shrub that only grows to about five feet tall and requires slightly more care than the Ray Hartman variety. It works great as a hedge and grows best in an area that has average to medium moisture that is well drained. The shrub is more vibrant when grown in full sun, but will tolerate some partial shade, especially in hot, summer climates, during which the plant may thrive even better. The Ceanothus delileanus Gloire de Versaille grows better in sandy loams or rocky soils that provide good drainage.
The plant can withstand drought conditions because of its thick roots that go very deep into the ground. Those roots, however, make an established shrub of this variety difficult to transplant, so plant it in a permanent location, preferably protected from strong winds.
Ceanothus Julia Phelps
California Lilac Shrubs
As with trees and groundcover, there are many different varieties of shrubs and we have only focused on a few of our very favorites.
The Blue blossom (Ceanothus thyrsiflorus) is an evergreen shrub endemic to the state of California and native to the Pacific Northwest. It is considered the hardiest of the shrubs and grows to be the largest and is a beloved plant to ornamental gardeners because of its bright blue flowers and yellow stamens, not often seen in ornamental gardens. The small, oval, glossy green leaves retain their shine through all seasons, and it makes a superb hedge that's even more beautiful when it comes to life with color.
The blue blossom is a hardy, low-maintenance shrub that will grow well, even in poor soil conditions and once established that can handle drought conditions like champions. No summer watering or soil amendments needed for this gorgeous shrub, which should make it especially appealing to gardeners. The blue blossom shrub blooms in May and June and can be planted in partial shade areas, as well as full sun. The shrub can grow up to about 15 feet tall at maturity. The shrub is self-fertile and, like all other California lilac species considered a nitrogen-fixing plant.
The Ceanothus concha shrub is a dense plant that sports an abundance of deep blue flowers which open from purple-red buds. The flowers, which bloom in late spring and early summer cover the entire shrub, which seems to be extremely attractive to hummingbirds and other birds; and butterflies. The concha received the Award of Garden Merit from the Royal Horticulture Society.
This shrub can grow up to about eight feet tall and has a spread that can be from six to 12 feet wide (the milder the climate, the bigger the shrub), and it is very difficult to transplant an established concha shrub, so plant it in a permanent location in well-drained clay, loam or sandy soil in full sun. The concha can be propagated by semi-hardwood cuttings.
Varieties of Groundcover
Although there are many different varieties of groundcover, these are two that are particular favorites of ours.
Point Reyes Ceanothus (Ceanothus gloriosus)
One of the groundcover varieties that is endemic to California is the Point Reyes Ceanothus (Ceanothus gloriosus), which can be found growing on seaside bluffs along the coastline of the San Francisco Bay Area, and on the slopes of coastal mountains. It is a flat, spreading shrub that can reach heights of up to five or six feet. This plant is highly recommended if you have a coastal garden where a compact form is desired.
If you are looking for a low-spreading evergreen groundcover, the Centennial might be a good choice for you. It only grows to be about six to 12 inches tall but spreads to up to eight feet wide These plants, sporting deep blue flowers, are able to withstand a considerable amount of shade and look great spilling down a slope of land or flowing down out of a decorative container.
© 2018 Mike and Dorothy McKenney