Blackberry

Lore & Background

Blackberries are perennial plants with biennial stems called canes. In the first year, a primocane grows 3–6 meters trailing on the ground, bearing large palmate leaves but no flowers. In the second year, the cane becomes a floricane, with lateral buds opening to produce flowering laterals. First- and second-year shoots bear short, curved, sharp thorns, though thornless cultivars have been developed since the early 21st century. Unmanaged plants form dense tangles, but can be controlled with trellises. The flowers bloom in late spring and early summer, each 2–3 cm in diameter with five white-pink petals. Each drupelet develops from a fertilized ovule; inadequate pollinator visits are the most likely cause of undeveloped ovules. Infection with raspberry bushy dwarf virus can cause incomplete drupelet development and crumbly fruit.

Reader's Guide

The blackberry holds significance as a commercially important fruit crop, with Mexico leading global production and Oregon as the top US producer. Its vigorous growth and ability to tolerate poor soils make it both valuable for cultivation and problematic as an invasive species, particularly Rubus armeniacus in the Pacific Northwest. Modern hybridization, primarily in the United States, has produced numerous cultivars with improved traits such as thornlessness, higher yields, and larger fruit. The development of primocane-fruiting and erect varieties has expanded growing options. The blackberry's ecological role includes providing food for caterpillars, deer, and mammals like red foxes and black bears, which disperse its seeds. Its legacy includes the loganberry, a hybrid with raspberry developed in 1880, and ongoing breeding programs at institutions like Oregon State University and the University of Arkansas.

Did You Know?

• When a blackberry is picked, the torus (receptacle) stays with the fruit, unlike raspberries.
• Rubus armeniacus (Himalayan blackberry) is considered a noxious weed and invasive species in the Pacific Northwest of Canada and the United States.
• The term 'bramble' traditionally applied to blackberry or its products, though in the US it applies to all members of the genus Rubus.
• Blackberry fruits are red when unripe, leading to the expression that 'blackberries are red when they're green'.

Botanical Identity and Taxonomic Tangle

The blackberry occupies a fascinating and often muddled position in botanical classification. Belonging to the genus Rubus within the rose family, it encompasses over 375 species spread across Europe, northwestern Africa, temperate Asia, and both Americas. Yet the very ease with which these species cross-pollinate and produce hybrids—both within the subgenus Rubus and between it and Idaeobatus—has made clean species boundaries nearly impossible to maintain. Historically, taxonomists have resorted to grouping related forms into species aggregates rather than forcing artificial distinctions. Even the fruit itself defies its common name: botanically, a blackberry is not a berry at all but an aggregate of tiny drupelets clustered around a central receptacle. This structural detail also separates it from its raspberry cousins. When you pick a raspberry, the hollow core remains because the receptacle stays on the vine; a blackberry, by contrast, carries that receptacle with it, leaving no hollow center. The result is a fruit whose identity is as layered and hybrid as the plant that produces it.

Two-Year Cane Architecture and Flowering

Blackberry plants follow a striking two-year reproductive rhythm that shapes every aspect of their cultivation. As perennials, they send up new stems—called primocanes—from their root system each spring. In that first year, the primocane grows vigorously, trailing along the ground to a length of three to six metres while bearing large, palmate compound leaves of five to seven leaflets, yet it produces no flowers whatsoever. The following year, that same cane transforms into a floricane: growth stops, and lateral buds burst open into flowering branches. Both first- and second-year shoots carry short, sharply curved thorns, though breeders in the early 21st century finally developed reliable thornless cultivars. Left unmanaged, the canes tangle into dense, impenetrable thickets that gardeners must corral with trellises. Flowers appear in late spring and early summer at branch tips, each roughly two to three centimetres across with five pale white-pink petals. Behind the scenes, genetics researchers have mapped the F Locus on linkage group 7 as controlling primocane fruiting, while thorn presence or absence is governed by a locus on linkage group 4—knowledge that now accelerates the selection of desirable traits in new crosses.

Ecological Ambivalence: Beloved and Invasive

The blackberry occupies a paradoxical place in the natural world, simultaneously cherished and combated. Across much of Europe, wild blackberry thickets are an integral part of the landscape, and picking their fruit remains a beloved seasonal pastime. Ecologically, the plants support a web of life: their leaves feed caterpillars and are relished by deer, while the concealer moth Alabonia geoffrella has been found developing inside dead blackberry shoots. Once ripe, the berries travel through the digestive tracts of red foxes, American black bears, Eurasian badgers, and small birds, which disperse the seeds to new locations. Yet that same vigorous growth habit—sending down roots from any cane that touches soil and pushing up suckers from established roots—makes unmanaged blackberries a persistent weed. In the Pacific Northwest of Canada and the United States, Rubus armeniacus, the Himalayan blackberry, has become a noxious invasive species choking urban parks and woodlands. Similar problems arise in Australia, Chile, and New Zealand, where both the Himalayan and evergreen blackberry (Rubus laciniatus) have naturalized and spread aggressively. An old folk expression captures the fruit's deceptive ripening: blackberries are red when they're green.

From Loganberry to Machine Harvest: A Breeding Story

The commercial blackberry industry owes much of its shape to a century and a half of deliberate crossbreeding, much of it in the United States. In 1880, Judge James Harvey Logan in Santa Cruz, California, created the loganberry, a blackberry-raspberry hybrid that opened the door to multi-species cultivars. The first thornless variety appeared in 1921, but its berries sacrificed much of their flavor, stalling progress for decades. The breakthrough came in the 1990s and early 2000s, when the US Department of Agriculture released cultivars such as Triple Crown, Black Diamond, Black Pearl, and the marionberry Nightfall—varieties bred for machine-harvesting efficiency, larger and firmer fruit, higher yields, and improved taste. Today, Mexico leads global production, shipping nearly its entire crop to fill off-season fresh markets in North America and Europe, a market long dominated by the EMBRAPA-bred cultivar Tupy until 2018. In the United States, Oregon stands as the top commercial producer, yielding roughly 19.3 million kilograms across 2,500 hectares in 2017. Because the many Rubus species hybridize so readily, most modern cultivars carry the genetic legacy of more than one parent species, making each berry a small monument to accumulated breeding decisions.

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