How to Grow Ceanothus — California Lilac

Ceanothus flower
Flowers of Ceanothus, California lilac

Ceanothus — commonly called California lilac–are handsome shrubs with dark-green leaves and commonly clusters of showy blue flowers, but a few bear white or pinkish blossoms. Ceanothus thrives where winters are not severe and where summers are not hot and humid. Ceanothus is native to hot, dry regions and grows well in dry infertile soil. 

There are about 60 species and hybrids of Ceanothus; some are evergreen and some are deciduous. Most are low to tall-growing shrubs; a few are tree-like. Ceanothus is native to dry scrub and woodland slopes. They are well suited for most dry or western native gardens. The low-growing or prostrate species and cultivars are good choices for groundcovers on dry slopes or in rock gardens.

 Ceanothus 'Concha' is one of the oldest Ceanothus hybrids.
Ceanothus ‘Concha’ is one of the oldest Ceanothus hybrids.

Get to Know Ceanothus 

  • Plant type: Broad-leaved evergreen or deciduous flowering shrub.  
  • Growing zones and range: Zones 4 to 10 depending on variety, mostly commonly Zones 7 to 9 
  • Hardiness: USDA Zones 7 to 9. 
  • Height and width: 6 to 9 feet 1.8-(2.7m) tall and wide depending on the variety; a few smaller and a few larger
  • Growth rate: Medium. 
  • Form and habit: Upright grower, tall and wide.  
  • Foliage: Long oval, dark green leaves that are toothed and veined.  
  • Flowers: Profuse small blue, purple, pink, or white flowers in clusters; some varieties produce lilac-like spikes.   
  • Fruits: 3-lobed capsule.   
  • Bloom time: Evergreen species flower in spring; deciduous types in summer.   
  • Uses: Soft, informal hedge, screen, wind-break for coastal regions; low-growing Ceanothus are suitable for ground covers and rock gardens; taller ones for shrub borders.  
  • Garden companions: Western North American natives
  • Common name: California lilac   
  • Botanical name: Ceanothus 
  • Family name: Rhamnaceae
  • Origin: Mostly from Western North America, in particular California, but also from Meixico

Where to Plant Ceanothus 

  • Plant Ceanothus in full sun.  
  • Plant Ceanothus in well-drained or dryish, neutral to alkaline soil.  
Ceanothus thyrsiflorus
Ceanothus thyrsiflorus

When to Plant Ceanothus 

  • Ceanothus transplant easily in early fall or spring to well-drained soil with a neutral to alkaline pH.  

Planting and Spacing Ceanothus 

  • Space Ceanothus 6 to 9 feet 1.8-(2.7m) apart or further depending on the variety.
  • Training Ceanothus against a wall offers them shelter from the wind and cold.  

How to Water and Feed Ceanothus 

  • Give Ceanothus little water, except as noted.  
  • Let Ceanothus soil dry between waterings. 
  • Ceanothus fix their own nitrogen and so do not need additional fertilizer.   

How to Prune and Care for Ceanothus 

  • Pruning season for Ceanothus is early spring to keep compact. 
  • Prune Ceanothus evergreen lightly after flowering; deciduous forms can be cut back close to the ground.  
  • Give Ceanothus some protection from cold winds.  

Ceanothus Pests and Diseases 

  • Ceanothus most often die from overwatering and related fungal disease and root rot.  

Ceanothus Propagation 

  • Sow seed in a seedbed or in containers in autumn.
  • Root greenwood cuttings of deciduous plants and semi-ripe cuttings of evergreens in mid- or late-summer.
  • The large roots of eastern Ceanothus species can make them hard to transplant when mature. Propagation is difficult.  
 Californian lilac flowers, Ceanothus thyrsiflorus repens in spring garden.
Californian lilac flowers, Ceanothus thyrsiflorus repens in spring garden.

Ceanothus Varieties to Grow 

  • Ceanothus americanus, New Jersey tea, white-flowers species, hardiest of Ceanothus. It grows wild in Zones 4 to 8 from eastern Canada to Manitoba and Texas. In Colonial times its leaves were used as a substitute for tea. Low, broad, and dense at 4 feet (1.2m) tall and 5 feet (1.5m) wide, it produces small white flowers in 1-2 inch (2.5-5.1cm) terminal panicles in midsummer. The leaves, dark green in summer, may add some yellow to the landscape in fall. A good plant for inhospitable conditions. Transplants with difficulty. It has given rise to better flowering hybrids. 
  • C. gloriosus, Point Reyes Ceanothus, evergreen. Grows 1-1.5 feet (.3-.45m), spreading 12-16 feet (3.6-4.9m). Tough, spiny dark green leaves; light blue flowers. Does not do well in the dssummer heat. ‘Anchor Bay’ is more densely leafed, spreads half the distance, and bears deeper blue blossoms.  
  • C. griseus horiazontalis, Carmel Creeper, evergreen. Handsome, glossy-leafed; to 1.5-2.5 feet (.5-.8m) high and 5-15 feet (1.5-4.6m) wide. Light blue flowers. Sometimes suffers winter damage in the colder part of its range. ‘Hurricane Point’ grows 2-3 feet (.6-.9m) high and spreads rapidly to 36 feet (10.94m) wide. ‘Yankee Point’ is the same height but spreads only 8-10 feet (2.4-3.1m).  
  • C. ovatus, inland Ceanothus, a slightly smaller, denser plant than C. americanus, native from New England to the central United States, with shiny leaves, tiny white flowers, and red seed capsules in summer. Provides food for quail and other birds. Zones 4 to 6.  
  • C. thyrsiflorus, native to California and Southern Oregon; one of the hardiest evergreens, large and vigorous, cold-sensitive, but lovely. Grows up to 20 feet (6.1m) tall and wide with arching branches. It combines glossy leaves with 3-inch (7.6cm) spring flower spikes that range from light to dark blue. Hardy in Zones 8 to 9 or 10; it can grow to 21 feet (6.4m).  
  • Hybrid Ceanothus are widely grown along the West Coast, from British Columbia to southern California, and inland in warm regions of Zones 7 to 8. Known as Blueblossom or California Lilac, reaching 6-12 feet (1.8-3.7m) tall and usually evergreen, hybrid Ceanothus are attractive in informal hedges and as specimens.  
  • ‘Concha’ a 6×6 feet (1.8×1.8m), which bears dark blue flowers, more tolerant of humidity than others. 
  • ‘Dark Star’ evergreen, tall, 8-10 feet (2.4-3.1m) wide. Tiny dark green leaves; cobalt blue flowers. Similar to ‘Julia Phelps’.  
  • ‘Frosty Blue’ with large blue flowers frosted with white.  
  • ‘Joyce Coulter’ a low, mounding plant 2-4 feet (.6-1.2m) high and 8-10 feet (2.4-3.1m) wide, with medium blue flowers.  
  • ‘Julia Phelps’ a 4-8 feet (1.2-2.4m) tall shrub that bears indigo-blue flowers, more tolerant of humidity than others.  

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