Marionberries: What They Are, How They’re Grown, and Why They’re So Prized

It’s as if Oregon's Willamette Valley—a fertile slice that runs between Eugene and Portland, about 70 miles inland—was created to grow berries. The cool, mild winters and warm-but-comfortable summers create the perfect microclimate for trailing berries to thrive. Bushes of blackberries, many different varieties, cling low to the ground to survive winter, and don’t turn to jam on the plant under summer’s scorching sun.

Oregon is home to only one true native blackberry plant, Rubus ursinus, a shrub with prickly branches that produces sweet, oblong berries. And though it’s a perfectly plump, multi-faceted fruit, scientists and horticulturalists with the US Department of Agriculture and Oregon State University have long worked together to cross-breed berries, seeking higher yields and even more fragrant fruit. Plenty of delicious new berry cultivars have come out of this partnership, but the marionberry is the prized jewel.

How Marionberries Are Grown

The birth of this particularly sweet berry, led by USDA horticulturalist George F. Waldo, involved crossing a Chehalem blackberry with an olallieberry, a blackberry cultivar with native Rubus ursinus in its parentage. The new hybrid and its potential were first noted in 1945; the berry was tested, mainly in Marion County, Oregon, until its official release in 1956. “Marion is a new blackberry that shows promise of meeting some needs of Oregon’s small fruit industry not fully met by the most widely grown blackberry varieties, Thornless Evergreen and Boysen,” Waldo wrote in a pamphlet, noting that the plant produced more fruit that ripened faster, and its “fruit quality has been generally superior to that of both varieties.”

Blackberries, raspberries, and marionberries are all known as caneberries, a family of berry varieties that produce fruit on woody vegetative shoots called canes. Marionberry plants typically produce just a few long canes (often around 16-20 feet long) that are easy to train and handle, making it an easy option for growers in any operation. They also produce pretty massive berries compared to other varieties.

While growth potential and ease of growth are obviously important factors in a cultivar, what's made the marionberry so successful is its balanced taste, which makes it ideal for preserves, jams, and pie fillings.

Why Marionberries Are Prized

“It’s sweeter than most other berries, but not overly so,” says Linda Strand, commissioner of the Oregon Raspberry & Blackberry Commission, and sales manager of Columbia Empire Farms. “In blind taste tests around the country, people always prefer it. It’s our gold standard in the industry.”

According to Bernadine C. Strik, professor of horticulture and berry crops specialist at Oregon State University, that perfect flavor comes down to chemistry: Marionberries have a 14% sugar concentration, 1.5% acidity, and a pH of 3.2, which is similar to the pH of a sweet strawberry. For non-horticulturalists, that means it’s delicious.

“When someone tastes a marionberry, there's that real balance between sugar and acid, which is really required when you process something,” says Strik. “If something's really sweet and low acid, it comes across as very bland with no flavor, fresh or processed. And if something is too high in acidity, then of course it's unpalatable unless you add sugar, and that tends to be a little less desirable to consumers.” Marionberries really need no accompaniment, and are somewhat easier to eat than other caneberries because of their tiny seeds.

While marionberries are sometimes marketed as being seedless, and eating one you’d assume that was accurate, a seedless berry is actually impossible, according to Stirk. But marionberry seeds are essentially undetectable to the tongue—they are extremely flat and thin, and evenly coated with a gelatinous material that helps them slip by without notice.

Easy to grow, and growing in popularity, the cultivar blew up in Oregon and in surrounding states, becoming the most popular berry in the region. Marionberries still account for about 25% of the state’s berry production, an impressive feat for a cultivar developed over 70 years ago.

In the ’90s, the industry wrestled with a small public relations crisis as people began associating this popular berry with Marion Barry, the disgraced former Washington DC mayor. Barry, who died in 2014, had made a name for himself as a civil rights leader, but was caught in an FBI sting operation in 1990 and ended up serving time in prison as a result. Strand recalls a runner with Late Night with David Letterman calling to order marionberries for a bit on the show about Barry.

How Marionberries Are Harvested

Today, marionberries are known for being the perfect berry for eating out of hand, and for processing. Sweet and smooth, they’re ideal for making preserves, jams, fruit spreads, pie fillings, sauces, crisps, crumbles, and more. Because they were bred more for flavor than durability, these berries don’t travel well outside the Pacific Northwest. And, unfortunately, marionberries aren't grown outside of the Pacific Northwest because it's one of the few regions in the world that specializes in harvesting and processing this type of berry.

Though they're fragile, advanced harvesting methods consistently preserve their flavor and texture in processed products. Other berry varieties are sometimes harvested in large batches. Since berries tend not to ripen all at once, massive harvests yield a mix of ripe and unripe berries. Marionberries, on the other hand, are harvested very selectively. During the short four-week season that kicks off around Independence Day, the berry fields are picked every few days with finely tuned row machines that vibrate the plants at very specific frequencies, which causes only the ripe berries to fall off for collection.

As Oregon became known for the cultivar, an effort in 2009 aimed to make the marionberry the official state berry. The action was supported by most legislators but was ultimately abandoned when a prominent berry producer claimed a focus on one specific berry variety might hurt the sales of other varieties.

While marionberries have exploded in popularity, there are still disadvantages that horticulturalists are trying to solve through breeding. Marionberry plants are thorny, making hand-harvesting tricky and rare, and they are less cold-tolerant than some other varieties, leading to variance in production from year to year. Two other cultivars developed under the same program by the late horticulturalist Chad Finn—Black Diamond and Columbia Star—sought to solve these issues and have risen in popularity, but haven’t surpassed the 1956 cultivar in terms of overall quality.

“I don’t think we’re close to improving on the marionberry,” says Stirk, seemingly convinced of its relative perfection, among berries, “at least not in the near future. I think its market share could shift slowly, but in terms of it being a standard, I don’t see that changing anytime soon.”