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Rubus Ursinus: A Guide to the Elusive Pacific Blackberry

Blackberries and a raspberry, probably doing a mating dance
PHOTO BY EMILY GREEN

Hiking last year in La Tuna Canyon, as my guide identified the streamside plants that we passed, I was gripped by a craving that only the late-winter mention of an early summer fruit can provoke. At the time, there were only March flowers on the trailing and thorny canes of what my friend, a botanist, at first called Rubus ursinus, then translated as being our native blackberry, before casually adding that this was a wild progenitor of the loganberry, boysenberry, marionberry and youngberry.

Loganberries! Youngberries! These are the caviar of blackberries, their dark wine flavors sweetened and brightened by interbreeding with raspberries. As I stood in the canyon bottom, staring at the then berryless blackberry bush, my friend added, "You know. This is the plant that gave rise to Knott's Berry Farm."

That poor man's Disneyland in northern Orange County indeed began in the 1920s as a farm with a roadside stall selling fruit, pies and jellies. Only in Southern California would Walter and Cordelia Knott have enticed people with blackberry jam before turning to roller-coaster rides expressly designed to nauseate visitors. Still, it was the stoop labor and steaming kitchen of this pair of libertarian old-timers that popularized a blackberry-raspberry hybrid called the boysenberry.

I had to know more about that cross and its local parent: Where to find native blackberries in nurseries and farmers markets. How to grow them. How to have my own version of the Knott's Berry Farm, where the only amusements were berries.

It turned out that many species of blackberries — like their distant cousins, roses — grow in most places around the world that are not rankly tropical, desert or permafrost. The Pacific blackberry of the sort growing in La Tuna Canyon was discovered in its native ranges from Canada to Mexico many different times, enough to accumulate a string of synonyms before Western botany settled on the Latin name Rubus ursinus; rubus for "bramble" and ursinus for "bear." Check out YouTube footage of bears eating blackberries and the reason for the name soon will become clear.

Nobody's quite sure when or how raspberry chromosomes first began popping up in Pacific blackberry genetics, though the incursion may be behind Rubus ursinus' combination of delectability and squishiness. These raspberry notes were steadily reinforced when, over the last century, gardeners began both accidentally and deliberately crossing Rubus with raspberries to produce what became boysenberries, loganberries, youngberries and that Oregon classic, marionberries.

Though it may fluster snobs, these fruits can all safely be grouped in a general way as blackberries. Oregon plant geneticists do it on the grounds that the fruit of the crosses still pulls away from the stem the way that blackberries do. It's also a helpful reminder that, while all are red when young, they're not ripe until they're black.

The hope of finding any member of the Rubus ursinus school of blackberries ripe in supermarkets is a pipe dream. A breeding program at a USDA research station in Corvallis has supported Oregon's world-famous jam industry, but the Pacific blackberry's susceptibility to leaf disease, the plant's preference for temperate growing conditions, difficulty of harvest and the explosive tenderness of the fruit have combined to leave the supermarket fresh-blackberry trade dominated by tougher, grassier and even bitter-tasting fruit derived from Eastern U.S. and South American stock.

To sample what USDA plant geneticist Chad Finn describes as the unique intensity and fragrance of our own Rubus ursinus, you need to either grow your own or watch farmers markets with bearlike intensity.

When it comes to growing your own, Pacific blackberries and their raspberry-infused progeny are considered to be "trailing," which means they flop over instead of growing upright, so make sure you have a large run of trellising. Chain-link fence will do. Call ahead to any nursery before expecting availability. Once choosing plants, look for thornless Rubus ursinus, or the most beloved of the raspberry crosses: olallie, Marion and boysen. If the store doesn't have any of the above, ask them to order a "Black Satin" from Monrovia Growers, which supplies most leading nurseries.

Finding youngberries or loganberries probably will take seeking out specialist suppliers such as the Bay Laurel Nursery in Atascadero, begging for cuttings at meetings of the California Rare Fruit Growers, or even contacting the Agricultural Research Service in Corvallis to make an "accession request" from its germplasm repository. If you choose this last option, send a donation. It's being starved of funds, no small thanks to the libertarian movement given such a boost in California by the boysen king himself, Walter Knott.

When planting Rubus ursinus and its various cultivars, give the plants humus-rich, well-draining soil. Pacific blackberries have not yet been bred so that they can fruit on new growth, so you will need to keep track of what's new wood (that will fruit next year), what's year-old bud wood (that will fruit this year) and what's spent cane. As you prune to keep the fruit accessible, you'll understand the advice to always look for thornless versions. Yvonne Savio, the local leader of the University of California Master Gardener program, uses clothespins to tie her berry branches to wire supports. This works.

Mulch the plants well. Crown rot, a fungus that can kill overmulched fruit trees, is not an issue with brambles, according to Altadena rare-fruit grower and cook Kazi Pitelka. Irrigate generously. Because the leaves can develop moisture-related diseases, Pitelka prefers drip irrigation, which leaves the foliage dry, though she showers her blackberries every so often to rinse away smog and dust. Planting instructions written for rainier climes will specify full sun. Along the relatively foggy coast in Los Angeles, adhere to this. In the hotter areas such as the valleys and foothills, consider the kinds of partially shaded spots that the wild plants themselves select.

At farmers markets, there is no guarantee that what you see will be a Pacific blackberry and not an Eastern interloper, so shop with your nose. Eastern berries lack our native's heady aroma. Two growers questioned for this article said they were using Eastern berries bred in Arkansas, with one adding that the disease resistance of the Eastern fruit made it easier to meet organic growing standards.

UC Riverside pomologist David Karp, who writes a farmers market column for the Los Angeles Times, makes no secret of his favorite vendor, Kincaid Farms in Redlands, whose berries all have Rubus ursinus genetics, flavor, aroma and perishable ways.

When Kincaid boysens and youngberries start arriving in May and June at the Santa Monica Farmers Market, what you do with them will depend on their sweetness. The sweetest should be what Pitelka calls "field canned" — eaten while picking or shopping — while the tarter ones are perfect for jam. According to Pitelka, "The marionberry and loganberries really shine when they're cooked. They have a bright tartness to them that makes the jam more exciting." She also recommends them for quick syrups to top off ice cream, dropping in red wine vinegar for use in summer salads or steeping in vodka for liqueurs. Then there are pies, which during marionberry season in Oregon are served with a white line of powdered sugar on top, says Pitelka, a joke about the former Washington, D.C., Mayor Marion Barry, who was caught with cocaine.

If you see blackberries coming to farmers markets now and continuing for a long spring-summer-fall season, chances are good that they are not Rubus ursinus. My sense, after conducting a straw poll among blackberry growers, is that new Eastern hybrids will dominate California stalls in years to come.

And so, here in Los Angeles, the best chance shoppers have of encountering our fragrant, ever-more-rare native blackberry may well lie in wild canyons, or in private gardens where the keenest kitchen gardeners keep them pinned to suburban chain link.

Emily Green, a freelance journalist based in Altadena, has written about food and gardening for the U.K.'s Independent, The New Statesman and the Los Angeles Times. She blogs at chanceofrain.com.


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