Ceanothus

The west’s best blues

This genus of shrubs is native primarily to the west coast with the majority of species in California and then Oregon. We love ‘Wild Lilacs’ as they are sometimes called for several important reasons.

They represent excellent climate adaptation. Almost all are native to winter wet/summer dry conditions. They thrive in our climate with little intervention from the gardener. Flowers: blue- no other shrub comes close to the display of blue flowers housed in this genus. The most blue cultivars and species hail from central and northern California and have been grown in our region for eons. Fast growing and extraordinarily drought tolerant they cruise through our dry summers with no visible signs of stress. In fact they loathe the combination of wet/warm soils. So no summer water is advised.

They range from large shrubs to ground covers and are useful in a host of situations. Full sun and average well drained soil including clay soils on slopes. They even fix nitrogen with their roots which means they earn their own lunch. Lifespan: typically they live on average 10 years but for the ground cover types which persist quite a bit longer. They make ideal plants for new gardens as they grow rapidly and even years after their demise the soil beneath them remains enriched, loose and friable. A great place to grow tomatoes.

Ceanothus are Oregon’s largest genus of shrubs. A total 13 species populate the state from the coast to the high Cascades. In Southwestern Oregon a conglomeration of species even results in hybrids. It should be said that there are several species of native Oregon Ceanothus that are spectacular in the wild but resist garden culture with a vengeance. Ceanothus pumila  Siskiyou Mat and Ceanothus prostratus Squaw mat (sic) are amazing when seen in bloom  in the spring. Its tempting to fall in love with the idea of replicating garlands of blue as you see Ceanothus prostratus on the rim of Crater Lake. Or to drape a patch of Siskiyou mat over a boulder. There must be a secret to their cultivation. As of yet we have not found it. Other native Ceanothus species make exemplary garden plants. Both Ceanothus thyrsiflorus and its cultivars and Ceanothus cuneatus are incredibly successful garden plants.

We have introduced several varieties of Ceanothus thyrsiflorus  native from Lane county Oregon to Santa Barbara County California and we’re always on the search for more Oregon cultivars. Water them until you see them start growing in earnest and then taper off. And then only the water that falls from the sky.  To prune, tip prune after blooming to resize, encourage density. Usually it is not necessary. The size of Ceanothus is completely dependent on the fertility of the soil. Rich soil HUGE, poor soil restrained. They make wonderful urban shrubs- tolerant of extreme reflected heat as well as hot dry places.

Ceanothus are very important for spring pollinators. A shrub in full bloom is a fascinating mass of bees, hover flies and many more pollinators. Some of our earliest butterflies to emerge also feast on Ceanothus. There is a place and a use in every garden for this fascinating group of west coast natives.

Climate Adapted Plants for Gardeners in the PNW

Ceanothus ‘Concha’

Big and arching evergreen shrub that becomes an unbelievable sea of ultramarine blue flowers in April. To 8′ x 8′ very quickly in full sun and well drained soil. Amenable to clay if unwatered in summer. Once established NO summer water at all. Grows quickly to its ultimate size give it room. Leaves burn below about 12ºF but recovery is rapid in spring and seldom sacrifices blooms. Rapid growing in our climate it consorts well with native wildflowers and especially bulbs.  Completely drought adapted in our climate. One of the most stunning wild lilacs ever released. Pictured below at an elementary school. Planted on the playground, the children use it as a shelter. Kind of cool.

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Ceanothus ‘Victoria’

This is one of the most popular shrubs in western Oregon of the last two decades. And rightfully so. This wild lilac sports excellent cold hardiness, prolific flowers, and glossy handsome evergreen foliage year round. A strong growing shrub that can literally explode in growth in rich soil but is much more restrained in poorer mediums. Remember this when planting it. It performs the best in average, un-amended soils in full sun with regular summer water for the first season to establish and then none in subsequent years. Sky blue flowers are profuse covering this dense shrub in a haze of color for 3-4 weeks in May to June. Later blooming that most other Ceanothus. This good looking shrub is so durable its made its way as  highway verge mass plantings but it is just as stellar of a garden plant as well. Cold hardy to about 5ºF- it survived -5ºF in the southern Willamette Valley in 2013 by freezing to the snow line and then vigorously re-sprouting. Durable, dependable Ceanothus. Avoid the summer heat + water that it abhors- it leaves it open to root water molds that can do it in and fairly quickly. Excellent shrub for the beginning gardener. Loved by pollinators of all kinds and is virtually rolling in bees during its fabulous bloom. NOT DEER RESISTANT. Most likely a hybrid with C. thyrsiflorus which must be responsible for at least half of its make up. Found in Victoria, Canada- hence the name. Likely it is the old cultivar ‘Skylark’ that was re-named upon its survival there of a hideous winter. The old name was forgotten and the glee of survival and discovery led to the renaming.  To be clear ‘Victoria’ and ‘Skylark’ are exactly the same thing. Very fast growing to on average 8′ x 8′. Excellent with all west coast natives. Blooms simultaneously with yellow Halimiums. A fantastic floral and cultural combination.

below photo credit: Jane Finch-Howell

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Ceanothus ‘Blue Jeans’

One of the cold hardiest blue flowered cultivars and one of the earliest to bloom as well. An open spreading shrub with prickily deep green leaves. In March/April the whole shrub is obscured in violet blue clouds of flowers. Upon first viewing in bloom most people are shocked at how showy this evergreen shrub is.  To 7′ x 5′ in five years in any well drained soil with little to no summer water. Very adaptable to clay soils, especially on slopes- as with all Ceanothus avoid boggy sites. One of the toughest cultivars that also takes very well to pruning which should be done after blooming to increase density if needed. Blooms on wood from the previous year and the button shaped flower clusters are so profuse that they obscure the foliage.  Tolerates blasting reflected heat and is great in hot urban situations. And makes a wonderful informal hedge for wild areas. Full sun. Moderately deer resistant- unusual for a Ceanothus. Cold hardy to 0ºF. The cultivar name might obliquely refer to the flower color but its an apt comparison to this tough , tough, shrub as well. No summer water.

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Ceanothus ‘Italian Skies’

A UK selection of our own west coast native wild lilac. And they did a good job. Large mounding evergreen shrub that puts on a spectacular display of deep blue flowers for nearly all of April into May. Fast growing to 5′ x 7′ very quickly in average well drained soil. Little to NO summer water. This cultivar has HUGE trusses of scintillating blue flowers. The largest of any Ceanothus that we grow- the reason why it is such a brilliant plant in bloom. Loved by pollinators of all kinds and especially tempting to large black and yellow bumble bees. Prune after blooming if you need to re-size the plant. Good cold hardiness. Best in a hot aspect. Good job to our friends in the UK.

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Ceanothus 'Midnight Magic' xera plants

Ceanothus ‘Midnight Magic’

We’ve been impressed with this extraordinarily deep blue flowered Wild Lilac released by Suncrest Nursery. A fine textured deep green evergreen shrub to 4′ x 8′ and forming a graceful cascading dome. Profuse cobalt blue flowers appear for 2-3 weeks in April. Extremely drought tolerant shrub for full sun and average to poor well drained soil. Little to no summer water required. Locate out of the path of subfreezing gorge winds. One of the most graceful and showiest of the genus. Grows very quickly to its ultimate size. Excellent performance on steep hillsides. Covers the ground like an umbrella with an great, intense, flower color. Excellent underplanted with yellow Pacific Coast Iris.

 

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Ceanothus cuneatus ‘Blue Sierra’

For cold gardens this is an excellent cultivar and its a version of a species native to the Willamette Valley south into California. Small green wedge shaped evergreen leaves on an arching, somewhat angular shrub. In April and May clouds of soft violet blue flowers swarm the whole shrub. Beautiful. To 7′ x 7′ very quickly in poor to average well drained sites. No summer water once established. Handsome at all times. Excellently adapted to rough urban life where compacted soils, reflected heat and little water is present in summer- thrives in all those conditions. Full sun. Easy. Surveys by the California Chaparral Institute report that this is the most common component shrub of that community in both California and Oregon. Fixes nitrogen with its roots and is common following disturbance. Classic west coast shrub.  Oregon native plant.

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Ceanothus cuneatus ssp. cuneatus ‘Adair Villiage’

This is a Willamette Valley  native form of Buckbrush found in the SW part of the Valley. This species is found historically from the Portland/Oregon City area in the Willamette Valley and  throughout the southern half of the state well into California. It has lost large areas of its northernmost natural range to development and fire suppression. It is a fire adapted species that requires disturbance to distribute. Thats a pity because this is a fantastic native shrub for hot dry sites. It is now employed by ODOT for freeway plantings and we are happy to see that. A large, angular evergreen shrub with small deep green paddle shaped leaves. In April the whole shrub is swarmed with pure white flowers.This is a beacon to all pollinators and the sweetly fragrant flowers will literally be buzzing in bloom.  Fast growing incredibly tough shrub for areas of intense drought and reflected heat. To 8′ x 8′ very quickly in any soil that does not become boggy. Excellent performance in tough urban situations. Irresistible to bees and butterflies. Extremely cold hardy to below 0ºF. No summer water. Moderate deer resistance. Oregon native plant.

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Ceanothus gloriosus ‘Emily Brown’

The glory of this large, wild evergreen shrub occurs in April when the branches are awash in deep violet blue flowers.The darkest hue among this species. A fast growing very large shrub to 4′ tall  by 12′ wide in time. Excellent for wild uncultivated areas. A handsome spreading deep green evergreen of great drought tolerance. Tolerates most soils that never become boggy. Good cold hardiness to 5ºF. No summer water when established. Loved by bees and butterflies. Takes well to pruning. Blooms on wood from the previous year, prune if needed after blooming. Excellent pollinator shrub for steep hillsides, rough areas. Evergreen foliage is handsome year round. Tolerates part shade. Blooms best in full sun. Photo below by Evan Bean.

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Ceanothus gloriosus ‘Pt. Reyes’

The most popular ground cover Ceanothus and an important plant in our climate. Evergreen ground cover shrub that covers the ground densely. In March the entire plant is smothered in light violet blue flowers. Stems root where they touch the ground making it a valuable erosion control. Full sun to light shade in any well drained soil. Excels on steep slopes. To 10″ tall and 3′ wide very quickly. Plant on 3′ centers for a fast dense ground cover. If the shrub grown as a ground cover gets too tall it may be sheared after bloom has ended. Water to establish for the first season, this also speeds growth.  Excellent performance in Hellstrips. Little water once established. Moderate deer resistance.

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Ceanothus impressus ‘Dark Star’

Easily one of the showiest wild lilacs commonly grown in our climate. Tiny almost black/green warty foliage is completely covered by masses of foamy deep cobalt blue flowers for several weeks in April into May. One of the showiest cultivars. The depth of blue is amazing. Very few plants can match the intensity of the hue blue.  Fast growing evergreen shrub to 6′ x 8′ in three years. Full sun and average, well drained soil. Light consistent water to establish then none. Site out of subfreezing east wind which will not kill it but can burn it badly. Easy, spectacular, fast, west coast native shrub. Note: The size of Ceanothus has everything to do with the fertility of the soil and access to water. Poor to average soil is best for a more moderate rate of growth  and not as huge of a shrub.

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Most Ceanothus are famous for their intense blue and profuse flowers, this interesting shrub has the typical masses of sky blue flowers which obscures the tiny warty foliage. To 5′ x 8′ and spreading wider than tall it becomes a cloud of blue in April and pollinators take notice.  Rolling in bees and every other awake pollinator a shrub in full bloom is a buzzing fountain of activity. Fast growing, wiry, dense shrub with extraordinarily dark green tiny leaves. This gives the shrub the distinct appearance of a cloud. Full sun  and average to poor soil including heavy clay soils that dry in summer. No summer water once established. Remarkably drought adapted west coast native shrub. Very easy to grow large, showy, shrub for wild areas, blasting hot urban hell scapes. Not totally deer resistant but better than most other species. Excellent performance at the Oregon coast. Endures sandy substrates and even a bit of salt wind. Attracts some of the first butterflies to emerge. Cold hardy to slightly below 10ºF for brief periods. Recovers from cold damage completely by bloom time.

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This form of Blueblossom we found on the southern Oregon coast in the far northern part of Curry County. There seems to be two forms of Ceanothus thyrsiflorus in Oregon. The immediate coastal species up to Lane county has broader leaves. Inland you find a much taller form with smaller juvenile leaves. An example of this is our large selection ‘Oregon Mist’. This is the standard broad leaved form  you find adjacent to the beach. Glossy rounded leaves are lustrous and deep green year round. In late April to early June an extended period of profuse sky blue flowers. Adored by pollinators and rolling in grateful bees.  A large native shrub with a rounded outline. To 8′ tall and possibly a little wider in AVERAGE soil in 5 years. Amended soil leads to prodigious growth and lack of hardiness.  Fast growing low water shrub for full sun to very light shade. This plant that we collected in the wild is actually very similar to the cultivar ‘Victoria’- the primary difference is earlier bloom by several weeks. And a slightly lighter blue flower. This is a good standard form of the beach species as found in our state. Its been cold hardy to 5ºF with good pest free foliage. Ceanothus fix nitrogen with their roots and improve the soil. Also, years of detritus from the shrub collects to form wonderful enriched soil as well. Average life span increases the less this plant is watered once established but expect 9-15 years. Durable shrub for urban to rural places. Extraordinarily drought adapted as well as tolerant of dry clay. Pretty and utilitarian. Available, autumn 2020. Oregon native plant.

Xera Plants Introduction 

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Ceanothus thyrsiflorus ‘Oregon Mist’

Greg and I found this distinctive form of Coast Blue Blossom in the wild. This species ranges from Lane County, Oregon to Santa Barbara County, California. A fast growing seral species that follows fire and disturbance. Very near the location where we discovered this handsome small tree was to the largest Ceanothus thyrsiflorus ever discovered in 1925- it was nearly 30′ tall. This is a large and fast growing evergreen tree with copious amounts of scintillating flowers.  It has smaller deep green leaves and huge trusses of soft turquoise flowers in late April to early June. A tall growing tree/shrub that attains heights of 15′ very quickly if allowed. This drought tolerant native takes very well to pruning too- which should be done after blooming. Full sun and average well drained soil- including clay soils. Little to no summer water when established. Excellent for use as an instant screen or informal hedgerow. Pretty in the background of dry borders. Loved by bees and butterflies in bloom. Very easy to grow native evergreen shrub that should be used more. Life span 15-20 years. Oregon native plant.

Xera Plants Introduction.

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Ceanothus thyrsiflorus ‘Rogue Sky’

A selection of Coast Blue Blossom or Ceanothus thyrsiflorus that we made very far inland from its natural range in SW Oregon. Typically relegated to the coastal strip we found this variety more than 35 miles inland. This improves cold hardiness. A rapidly growing shrub/tree to 16′ tall and 8′ wide in 7 years. Robin’s egg blue flowers smother the whole plant in May. Extremely drought tolerant this fast grower may be either used as a cool, evergreen, native, blue flowered tree or it may be pruned aggressively after blooming to limit the size- increase density create a screen or hedge. Loved by honey bees and all pollinators in general.  No summer water once established. Excellent background tree that delights in bloom but fades to a green screen the rest of the year. Plant with other drought tolerant plants- Arctostaphylos, Cistus, etc. Grows 3′-4′ per year when established. The flowers are a soothing blue- which is hard to capture in photographs. The effect in bloom is a blue cloud. Takes partial shade and the worst soils. Oregon native plant.

Xera Plants Introduction

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A very large growing, vigorous and pretty tree type Ceanothus native to the extreme SW part of the state. This fast growing evergreen tree (3′-4′ per year) puts on a huge display of soft blue flowers in  late April to early June. Full sun to light shade (high overhead shade) and average soil that drains. Adaptable to clay soils, especially on slopes and not watered at all in summer. Completely drought adapted, no water necessary once established. To 18′ tall and half as wide in 7 years. Great screen, blue flowered tree that is beautiful in bloom but fades to a background for the rest of the year. Prodigious pruning can keep it much lower and it makes a great large hedge in no time. Good cold hardiness to 5ºF. We chose this variety in the wild because it was found quite a bit away from the coast which increases cold hardiness and it was immensely heavy in bloom.  Prune AFTER flowering if needed. As a hedge or smaller plant it only requires pruning once a year- especially if strictly unwatered. Extraordinarily heavy bloomer. Pairs well with Madrone and Arctostaphylos.  Oregon native plant.

Xera Plants Introduction

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Ceanothus thyrsiflorus var. griseus ‘Kurt Zadnick’

What a surprise this very dark, dark, dark blue flowered Ceanothus has turned out to have excellent cold hardiness.  In our climate it is a low and spreading evergreen shrub with glossy leaves. To 3′ tall  by 6′ wide in 6 years. In April/May a profuse display of the darkest cobalt blue flowers mass over the whole plant. Its so dark that it can seem like shadows over the plant but closer inspection reveals the intensity of the color blue. Full sun to light shade in average soil. Tolerates clay soil as well as withering summer drought. Prune if needed lightly after blooming has ended. This is a great drought tolerant, heat tolerant low shrub for hell strips. No summer water please. Well scaled for hell strips, low massing or a higher ground cover for hillsides. Fast growing to its ultimate size.

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Ceanothus var. roweanus ‘Cynthia Postan’

One of our favorite wild lilacs with flowers as deep blue as any and great glossy dark, evergreen foliage. Not as big as Concha it is a large shrub none-the-less. To 5′ x 7′ and spreading. In April to May masses of intense cobalt blue flowers open from showy red buds. Amazing floral display that draws bees and pollinators from 5 counties around. Full sun and average to poor well drained soil. No summer water when established. Hardy to 5ºF and any winter damage that occurs (below 10ºF) recovers quickly and still blooms prolifically in spring. Excellent for no-water wild areas, for large hellstrips, sunny hillsides. The roots fix nitrogen and though its lifespan is but 10 – 12 years on average it enriches the soil in a wonderful way. Great shrub for a new garden. Avoid subfreezing wind.

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Ceanothus x deslilianus ‘Topaz’

Possibly the darkest blue flowering cultivar that blooms in the summer. This hybrid is technically supposed to be deciduous but for us it never has been. Large panicles of cobalt blue flowers erupt from the current seasons growth in June to July. Remove spent flowers and more may follow. To 5′ x 3′ in average to enriched soil with REGULAR summer water. Good drainage. Easy to resize as it blooms on new wood, it may be cut to as low as 18″ in early spring. Black seed capsules follow the flowers and persist until birds relieve them of their contents in autumn. Excellent in borders, as a specimen, or informal hedge-row. Not as drought adapted as most of the genus. This plant is best with consistent moisture through its bloom period- not boggy (ever) but consistent. Remarkable flower color- moody, deep indigo. Click on Ceanothus video in green script.

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