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Wednesday, December 5, 2012

Plant of the Month (December) : ‘Ray Hartman’ Ceanothus – Ceanothus arboreus x C. griseus ‘Ray Hartman’

'Ray Hartman' Ceanothus - Mother Nature's Backyard, 2017

It’s been an uncommon year throughout the world in 2012.  The ‘La Niña’ climate pattern, with an unusually dry and windy summer/fall, has local plants confused.  Some are blooming earlier than expected.  Among them is the ‘Ray Hartman’ Ceanothus (see above as it looks in 2017).

The genus Ceanothus contains about 50-60 species.  The evergreen species are primarily from California, while the winter-deciduous Ceanothus americanus is native to the eastern U.S. and Canada.  The genus is included in the Buckthorn family (Rhamnaceae) along with California Coffeeberry and the Redberries.   Ceanothus are often known by their genus name - Ceanothus – although another common name is California Lilac.

Several Ceanothus species are native to western Los Angeles County, including the Catalina/Tree Ceanothus (C. arboreus) from Santa Catalina Island.   The Ceanothus of Los Angeles County are members of the chaparral plant community, normally growing at elevations of 1000 ft or greater in the local foothills.   None are native to lower elevations like the Gardena area.

People fall in love with Ceanothus and want to grow them. That’s not surprising - they are beautiful evergreen shrubs.  But choosing a Ceanothus can be a gardening challenge.  Native plants tend to do best under their natural conditions, including light, soil characteristics, precipitation patterns, etc.  Most Ceanothus – whether from the local foothills or the Central/Northern California Coast – grow in conditions quite different from those in Gardena.   We chose ‘Ray Hartman’ because it’s known to be ‘garden hardy’ in our area.  But we need to remain aware that our conditions are not optimal for Ceanothus.   For example, our clay-loam soil drains more slowly than the rocky soil preferred by most Ceanothus. We’ll have to be careful not to overwater.  
‘Ray Hartman’ Ceanothus is interesting in several ways.  First, it’s a hybrid (cross) between two parent species: our local Ceanothus arboreus and the northern California Ceanothus griseus (sometimes also called C. thyriflorus var. griseus).   In scientific notation, a hybrid is denoted as follows: Parent species 1 x Parent species 2.   Whenever you see a scientific name with that format, the plant is a cross between two separate species.  A hybrid can occur naturally – bees are notorious for cross-pollinating – or be created artificially, usually by careful hand pollination. 

‘Ray Hartman’ Ceanothus is also interesting because it’s a named cultivar.  A horticultural cultivar is simply a plant variety that’s been selected specifically for gardens.  Cultivars usually have characteristics that make them particularly suited to gardens – nice size, flower color, drought tolerance, etc.   Like hybrids, cultivars can be naturally occurring (in the wild), selected by nurserypersons from plants growing in a garden or created by careful hand pollination.   Some cultivars are hybrids – others are not.  All cultivars are denoted as follows (with the cultivar name in single quotes):  Genus name   species name  ‘Cultivar name’. 

‘Ray Hartman’ Ceanothus (Ceanothus arboreus x C. griseus  ‘Ray Hartman’) is a hybrid cultivar.  You can tell that immediately by its name.   It was released into the nursery trade by Rancho Santa Ana Botanic Garden in 1948.  It’s one of the older California native cultivars and has a long history of use in S. California gardens.    With a bit of luck – and carefully watering – it will succeed in Mother Nature’s Backyard.

Hybrid plants may exhibit characteristics of both parent species.  ‘Ray Hartman’ Ceanothus inherits its size and form from its Catalina Ceanothus parent.  ‘Ray Hartman’ has a tree-like form and will grow quite quickly (2-4 ft a year to start)  to a final height of 10-15+ feet and about as wide.   Technically, ‘Ray Hartman’  is a large rounded shrub, but its large size and open, upright growth pattern make it a good candidate for pruning up as a small tree.  That’s what we plan to do with our ‘Ray Hartman’ Ceanothus.

When creating a ‘tree’ from a large shrub it’s important to not only choose the right species but also to select a young plant with a good basic structure.  Ceanothus species range in size from low-growing groundcovers to large shrubs.  So, it’s essential to choose the right Ceanothus for the job.   The basic structure, evident even in a young plant, will determine the future shape of a plant.  It’s important to find a plant with the right basic shape, even if it means searching through a number of one-gallon plants at the nursery.  Time spent in selection will be richly rewarded with a nicely-shaped tree or shrub in the future.

'Ray Hartman' Ceanothus pruned up as small tree.
Mother Nature's Backyard - 5 years after planting
Like other chaparral shrubs, Ceanothus take several years to become established. It’s best to leave them alone during the first few years, only pruning out diseased, damaged or crossed branches.  We just pruned out a few crossed branches that would have rubbed and caused bark damage this winter.

Start pruning a fast-growing Ceanothus in the second or third summer after planting, after bloom is finished and the weather is dry. If training a slower-growing type, you may want to wait until the 4th or 5th summer.  Start by removing several of the lowest branches.  Trim these off all the way to the main trunk, being careful not to prune into the bark ‘collar’ where the branch connects to the trunk.  When pruning a Ceanothus, never prune a branch greater than 1 inch diameter and never prune out more than ¼ of the branches.    

Over the next several summers continue to select for upright growth by pruning out branches that grow down or out.   Most Ceanothus have pleasing natural shapes;   your goal is to accentuate the natural shape.  After the first few years you’ll mostly be pruning out damaged, diseased or crossed branches.  

Another trick to producing a well-shaped Ceanothus tree or shrub is to tip-prune young branches during periods of active growth.  In nature, deer ‘prune’ the delicate (and tasty) ends of branches in spring/summer.  The plant responds with increased growth of side branches, creating a fuller plant.  Since we’ve no deer in Mother Nature’s Backyard, we’ll have to ‘be the deer’ with our pruners for a while.

Like its C. griseus parent, ‘Ray Hartman’ Ceanothus has shiny rounded leaves that are large for a Ceanothus (up to 1 inch).  Because it’s evergreen with minimal summer water it looks good year-round.   It’s most often used as a small tree or large shrub, but can also be planted as a large hedge/hedgerow or screen plant. Like most Ceanothus, ‘Ray Hartman’ can be grown in full sun to part-shade.

The medium blue flowers grow in rather long (3-5”) spike-like clusters.  While individual flowers are small, there are hundreds of sweet-scented blooms per cluster. In a good year, ‘Ray Hartman’ will literally be covered in blooms (see below).   Like many Ceanothus, ‘Ray Hartman’ may flower both fall-winter and spring (the main bloom season).

‘Ray Hartman’ is among the most garden-tolerant of all Ceanothus cultivars. It adapts to a wide range of soil types from sandy to clay and is a bit more tolerant of summer water than other Ceanothus.  It can take inland summer heat and is very drought tolerant once established (after the first year).  We recommend occasional deep water (or none nearer the coast) once established.  With our clay loam we plan to water ‘Ray Hartman’ deeply once a summer - in August, when summer monsoons often provide water to our local mountains.  

In addition to their other attributes, Ceanothus provide excellent habitat for birds and insects.  All Ceanothus are good for attracting bee and fly pollinators.  Ceanothus species are larval host plants for the beautiful  Ceanothus Silkmoth (Hyalophora euryalus (Boisduval, 1855)) along with manzanita (Arctostaphylos), gooseberry (Ribes), willows (Salix), alder (Alnus), and mountain mahogany (Cercocarpus betuloides).

Ceanothus seed is readily eaten by Mockingbirds, Bushtits and finches.  Larger Ceanothus species also provide important cover and nesting sites for local birds.   Planting a Ceanothus can be an important step to attracting more birds to your garden.  We’ll discuss ‘Ten Natural Ways to Attract Birds’ in our next posting (December, 2012).

'Ray Hartman' in Dec. 2012 - 10 months after planting

Our 'Ray Hartman' in December, 2013 (20 months after planting)

'Ray Hartman' in 2015 - 3 years after planting

'Ray Hartman' in 2017 - 5 years after planting
Note that all 5 years were drought years in our garden.

'Ray Hartman' in 2018 - 6 years after planting as 1-gallon.

Comment on your experiences with 'Ray Hartman' Ceanothus below.  Send your gardening questions to us at: mothernaturesbackyard10@gmail.com



  1. Hi! How does the Ceanothus Ray Hartman do in windy areas? 20 to 40 mile an hour winds? I would like to have two as my new sidewalk trees.
    I know they'll probably have an angled shape and I'm thinking that is fine...for now.

  2. I think they will do fine. But they will be shaped by the wind. In our garden, winds mostly come from the west. Our tree bends a bit to the east as a result.

  3. With respect to water requirements, how long does it take to 'establish' a Ceanothus Ray Hartman ? We just planted a young, 1 gallon sized, plant. Our soil is sandy and well drained. Should I water once a week for the first year during late spring and summer ?

  4. If you live in S. California (or other dry region) I'd water once a week through Aug. this year, then go to every 10 days for fall. You'll probably need to water every other week, during dry period (including winter), for the next two years. Even after that, you'll likely do best deep summer watering every month with sandy soil.

  5. Great post thanks. I'm happy to report that Ray Hartman grows well up in Seattle proper, 5 feet during the fist year in the ground. I've had to stake it because it grow too fast. It's also about to start blooming even though it's January. Two thumbs up.