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Gardening 101: Ceanothus

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Gardening 101: Ceanothus

March 7, 2024

California Lilac, Ceanothus

Are you a devotee of multitasking plants—meaning, you choose plants based on whether they serve many purposes? If your answer is yes, then I have a plant for you: California lilac. Not only are ceanothus colorful, but they are extremely low-thirst, low-maintenance, and pollinator-friendly. And though they burst forth with amazingly fragrant spring blooms, California lilacs are not related to true lilacs (Syringa).

Please keep reading to learn more about the other lilac:

California lilac spotted on A Leisurely Stroll Through the SF Botanical Garden in Golden Gate Park. Photograph by Michelle Slatalla.
Above: California lilac spotted on A Leisurely Stroll Through the SF Botanical Garden in Golden Gate Park. Photograph by Michelle Slatalla.

California lilac is a large genus of diverse, helpful, flowering trees, shrubs, and ground covers. Many are native to North America—with more than half a dozen native to Oregon, and many others only to California, which explains its common name. Adding to this diversity, some species are evergreen and other deciduous. You can generally tell them apart visually because the evergreen varieties have smaller (sometimes toothed), darker, and leathery leaves while the deciduous ones have softer, larger leaves. The flowers on both are most often fragrant, quite showy, and pollinator-attracting. Flower color ranges from white to pink to purplish-blue and electric blue. This explosion of blooms usually happens March into May. The other difference among them are their habit and ultimate heights. Some grow into spectacular trees 18 to 20 feet tall, while others creep along the ground and make great ground covers for erosion control and weed suppression.

A Ceanothus in bloom. Photograph by Andy\2boyz via Flickr.
Above: A Ceanothus in bloom. Photograph by Andy2boyz via Flickr.

While most gardeners believe that ceanothus suffer from a moderately short lifespan of 10 years or so, this is not totally accurate. These plants can live long lives—as long as you don’t kill them with kindness. Pamper these plants and you accelerate their demise. The culprits? Overly rich soil and too much water, soil amendment, or fertilizer. An interesting note is that the reason you don’t want to overfeed these plants is that some members of the genus are able to form a symbiotic relationship with soil fungi and microbes, creating nitrogen-fixing root nodules, meaning they make their own food. Plus, bad fungal diseases can arise from too much water and improper drainage.

The takeaway is that less is more with these plants—which should be good news to us overworked gardeners. Pro tip: The first warning sign is an excess of yellowing leaves. Once this decline begins, death usually ensues. So remember, focus on excellent drainage and a bit of tough love.

Popular Varieties

A \2-gallon pot of Ceanothus thyrsiflorus &#8\2\16;Blueblossom&#8\2\17; is \$\24.95 at Sparrowhawk Native Plants.
Above: A 2-gallon pot of Ceanothus thyrsiflorus ‘Blueblossom’ is $24.95 at Sparrowhawk Native Plants.
  • Ceanothus thyrsiflorus ‘Blueblossom’. This large evergreen shrub grows 8 to 12 feet high and just as wide and boasts bright blue puffed-shaped clusters.
  • Ceanothus griseus var. horizontalis is a garden favorite. This shrub is similar in habit to Ceanothus gloriosus but has glossy oval leaves. It can tolerate a bit of summer water but resents water-logged conditions.
  • Ceanothus gloriosus. Endemic to California seaside bluffs and coastal mountains, this shrubs grows low to 2 feet high and spreads to about 6 feet wide.
  • Ceanothus ‘Joyce Coulter’ is a mounding form with branches reaching 2 to 5 ft high and spreading to 8 to 15 feet wide. A heavy bloomer, it covers itself in spring with highly fragrant, medium blue, 3-inch flower spikes. It tolerates clay, summer irrigation, and shearing better than many other cultivars.
  • Ceanothus thyrsiflorus ‘Snow Flury’. I’m a big fan of this large shrub/small tree that grows to 12 feet or more. I love the profuse clusters of delicate white blossoms in the spring. Adaptable and more garden tolerant.

Cheat Sheet

Poppies and Ceanothus at the Rancho Santa Ana Botanical Gardens. Photograph by Bri Weldon via Flickr.
Above: Poppies and Ceanothus at the Rancho Santa Ana Botanical Gardens. Photograph by Bri Weldon via Flickr.
  • Flowers clusters are fragrant and full of nectar, which means they attract loads of bees, moths, and butterflies while also being food sources for these winged helpers.
  • A smart addition to a low-water, native, or habitat garden.
  • Larger evergreen shrubs make excellent evergreen hedges and screens and all sizes of ceanothus provide perfect cover for birds.
  • The blue blossomed ones look lovely paired with yellow/orange flannel bush and California poppies.
  • The species with sharper, smaller holly-like leaves are more deer-resistant than the large, rounder-leafed ones, but generally they are tasty to deer.

Keep It Alive

Phlox and Ceanothus prostratus, a groundcover. Photograph by Nicholas Turland via Flickr.
Above: Phlox and Ceanothus prostratus, a groundcover. Photograph by Nicholas Turland via Flickr.
  • Most California lilacs prefer full sun on the coast and afternoon shade inland for best flower production and overall health.
  • Extremely well-draining soil is key to success. Pro tip: If soil is heavy and sluggish, create mounds or plant on slopes.
  • Many are drought-tolerant and dislike summer irrigation once established. The first summer after planting, give your plant regular drinks of water, then drastically taper off.
  • Avoid heavy pruning and don’t get hasty and cut into old wood or expect dead branches.

See also:

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Frequently asked questions

Are California lilacs low-thirst and low-maintenance?

Yes, California lilacs are colorful, low-thirst, low-maintenance, and pollinator-friendly.

Are California lilacs related to true lilacs (Syringa)?

No, California lilacs are not related to true lilacs (Syringa).

What is the lifespan of ceanothus plants?

While most gardeners believe that ceanothus suffer from a moderately short lifespan of 10 years or so, they can live long lives as long as they are not overpampered.

How can I keep California lilacs alive?

Ensure they have full sun on the coast and afternoon shade inland, well-draining soil, avoid heavy pruning and summer irrigation once established.

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