A true blue Californian

THE farther one travels from Los Angeles, the better the chances of seeing California’s most ravishing native shrub, variously named backbrush, or snowbush, or pine mat, or whitethorn, or mountain lilac. There is a type for every county and it takes in more common names than shades of bloom. The botanical name for the genus is Ceanothus, pronounced see-an-OH-thus, and of the 50 species thought to exist in North America, 41 are native to at least some part of this state.

There are creeping ones that carpet the coastline, brush forms that green charred hillsides after fire, almost tree-like specimens that partner with the oak and pine forests, and, heartbreakingly, lonely stands sitting in the paths of the bulldozers now clearing Riverside County.

Although finding them in the wild is straightforward (follow the butterflies), if you want to see them in gardens the best place to do so is England. While staying in the London suburb of Richmond-upon-Thames, California nurseryman David Fross says he counted 37 different ceanothus in the gardens that he passed on the seven-minute walk from his hotel to the train station. Walking the same distance near his home in Arroyo Grande, in Central California, he says he saw two or three.

Walk the same distance in Los Angeles, and you would be unlikely to see one.

Oh, what we California gardeners are missing! Unless, that is, we take the last month of planting season in advance of winter rains to get reacquainted. Ceanothus are worthy for their foliage alone. Although some are deciduous, most sold in California are lush, evergreen, with stout leaves in deep, sturdy hues from olive to British racing green. There are enough species and cultivars to suit any garden style, says Bart O’Brien, director of horticulture at Rancho Santa Ana Botanic Garden. Ceanothus can come prostrate, shrub-like or arching. Some are scented, others have aromatic leaves.

Finicky gardeners can espalier them, the merely orderly can deadhead old inflorescences for more blooms, and the laissez-faire types among us can simply plant them in a garden bed and let them fill up with nesting birds and butterfly caterpillars as they produce great fountains of spring color.

Ceanothus flowers, great plumes of them, come in white and pink. Yet it seems inescapable that the reason specimens were snatched out of the American West hundreds of years ago and kept in constant cultivation in Europe was because the flowers came in so many shades of blue. It may be the most prized color in horticulture (witness the quest for the blue rose). No other plant, not lavenders, not salvias, not jacarandas, can match the range and stately intensity of ceanothus blue. Talking about his upcoming book, “Ceanothus” (Timber Press, March 2006), Fross reels off the blues: azure, madder, cerulean, cobalt, aqua, slate, cyanine. Sky blue. Levi blue. Blues so blue, he says, that they “tremble.”

TRUST the English and the French to have gone at all those blues so differently. Most of the French hybrids were developed by crossing an East Coast species, C. americanus, which brought cold hardiness, and a Mexican one, C. caeruleus, for the blue, says O’Brien. By contrast, British collectors worked California and kept working it, so that it was not unusual to see the garden hybrid Ceanothus ‘Cynthia Postan’ emerge out of the swirling mists of East Anglia.

The concentration of ceanothus in California -- 41 species here compared with three or four in the East and a smattering in South America -- is a result of our geography, says taxonomist Dieter Wilkin, vice president for programs and collections at the Santa Barbara Botanic Garden and coauthor with Fross on “Ceanothus.” As mountains formed and California developed distinct ecologies, ceanothus diversified with it during the last 30 million or 40 million years. So today there are species adapted to coastal climates, mountain ones, chaparral, woodlands and riparian habitats.

The trick to gardening with them successfully is understanding the role that they played in the wild, none more important than re-vegetating mountains and chaparral after fires, says Alison Berry, professor in the plant sciences department at UC Davis. In the wild, seeds need to be scorched to germinate. (Plant breeders scald them for the same effect.) A young stand carpeting a hillside after a fire does more than secure the soil against erosion. It fertilizes it. Nitrogen from the atmosphere is captured by the plant and transformed by root nodules into a new form of nitrogen that enriches the soil.

To “fix” atmospheric nitrogen in an available form for other plants, ceanothus needs the symbiotic bacteria, called Frankia, in its root system. To keep the Frankia healthy, and to allow ceanothus to perform as well below ground as it does above ground, it is crucial to resist the impulse to fertilize and water. Doing those two things is like giving an Oreo and a Coke to a diabetic. At a guess, this self-sufficiency is precisely why ceanothus is so rare in its native habitat. The hardest thing for any gardener to do is leave plants to their own devices.

IT seems odd that ceanothus should have survived in England, a country famous for rain. But Fross says it’s not a case of how much water but when that water is applied. Ceanothus adapt to the relatively wet climates of England and the Pacific Northwest, he says, because most of their water comes in the form of rains in winter, when the plants are growing and can deal with the dampness. Gardeners in those watersheds rarely, if ever, irrigate in the summer.

To achieve the same success here in California, depending on the situation inland or at the coast, O’Brien recommends only occasional summer water, as much to clean air pollution from the leaves as to dampen the soil.

Ceanothus has a reputation as short-lived. Five to 10 years is the going projection. The best flowering years are said to be from 3 to 7, after which, like dogs, they are said to calm down. But O’Brien says there are 30-year-old ‘Ray Hartman’ ceanothus flowering gloriously all over Southern California. In his seven-minute walks in England, Fross recalls meeting one gardener who loves his potted ceanothus on his front step so much that even though it outgrows its container every other year, he keeps specimens on show. “It’s worth it,” said the Englishman.

Here in California, all we need do to enjoy 10 times that number of scented blue springs is to pick our plants carefully, choosing the right species for the right locale. Forty million years of evolution and the plants will do the rest.

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BEGIN TEXT OF INFOBOX

A guide to bloom times

If only going native meant turning off the sprinklers. Alas, it’s not so simple. Standing at a specialist nursery staring down at 1-gallon pots, few of which are in flower during fall planting season, one wonders: Is that a tree or is it groundcover? The publication of two new books changes all that.

“California Native Plants for the Garden” (Cachuma Press, $37.95 hardcover, $27.95 paperback), due out this month, was written for the interested amateur. Three horticulturists -- Carol Bornstein of the Santa Barbara Botanic Garden; David Fross, founder of Native Sons wholesale nursery; and Bart O’Brien of Rancho Santa Ana Botanic Garden in Claremont -- provide a working manual on how to choose which native plant for what spot. In March, Fross will follow with a volume dedicated to ceanothus, this time writing with taxonomist Dieter Wilken. Here are some of the selections from both books covering bloom times from January to June.

Tree or shrub

Ceanothus cyaneus ‘Sierra Blue.’ Late spring bloom, through summer. “California Native Plants” says: “Vivid, dark masses of violet blue flowers, which hang from its stems in 8-inch-long clusters. This open, free-formed shrub reaches 15 feet or more in height and width. Fast growing and has polished, 1- to 2-inch-long leaves. Pruning will improve its form.”

Ceanothus ‘Ray Hartman.’ Spring bloom. “California Native Plants” calls it a striking selection with large glistening green leaves, rose-colored buds and profuse clusters of sky blue flowers: “It can attain 18 feet in height and width in three to five years.” Noted for its longevity, from 25 to 30 years.

Medium shrubs

Ceanothus ‘Concha.’ Late winter, early spring bloom. “California Native Plants” says: “produces 1 1/2 -inch-long clusters of luminous cobalt blue flowers ... narrow, dark 1-inch-long leaves glint appealingly in the sun ... graceful arching branches form a dense 6- to 8-foot-tall mound.”

Ceanothus impressus. Spring bloom, parent of the popular hybrid ‘Dark Star.’ Spreading shrub with dark green quarter-inch leaves and abundant cobalt blue flowers. “California Native Plants” says of ‘Dark Star:’ “Brilliant cobalt blue flowers ... fast growing, quickly reaches 6 feet with 6- to 10-foot spread ... most suited to coastal sites ... sensitive to water molds in poorly drained soils.”

Ceanothus ‘Skylark.’ Late spring bloom, early summer. Admired by Bornstein, Fross and O’Brien for “compact, dome-like form.” Their book adds: “Its curled, dark green, 2-inch-long leaves have a thick, resinous texture and its cerulean blue flowers bloom later than most ceanothus.”

Groundcover

Ceanothus maritimus. Winter bloom, January to February. Olive-green leaves, flowers from white to indigo. “California Native Plants” says: “Accent in dry border or highlight in a rock garden, slow-growing, long-lived ... may benefit from partial shade ... will grow in heavy soil that is adequately drained.”

Ceanothus ‘Centennial.’ Early spring bloom, creeping stems from 8 to 12 inches tall. Fross and Wilken describe it as low, spreading, small polished green leaves, cobalt blue flowers. Full sun on coast, shade inland, well-drained soils even suitable for woodland garden.

-- Emily Green

Emily Green can be reached at [email protected].