Blackberry

• 1. Introduction

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  Blackberry holds a remarkable distinction among fruits: it is not actually a berry at all. What most people call a blackberry is botanically an aggregate fruit, a cluster of small drupelets each grown from its own fertilized ovule. Yet this technical quirk has done nothing to diminish the plant's presence in human life across thousands of years. The remains of a Danish woman preserved in a bog for roughly 2,500 years contained blackberries in her stomach, making her one of the earliest documented cases of human blackberry consumption on record. That single forensic detail places this plant at the edge of prehistory. What came after spans continents, cultivars, invasive thickets, and a cultural mythology that extends from Irish folklore to the London Pharmacopoeia of 1696. The questions worth asking are not simply what the blackberry is, but why it spreads so aggressively, how it became a global commercial crop, and what it means that one of the world's most productive fruit plants is also one of its most feared weeds.

• 2. What Makes a Blackberry

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  James Harvey Logan, an American judge and horticulturalist working in Santa Cruz, California, crossed a blackberry with a raspberry in 1880 and produced the loganberry. That experiment worked because blackberries and raspberries are close relatives sharing the genus Rubus. The easiest way to tell them apart requires nothing more than picking one. When a raspberry is pulled from the vine, the torus, the receptacle connecting berry to stem, stays behind, leaving a hollow core. When a blackberry is picked, that torus comes with the fruit. The berry remains solid all the way through. The taxonomy of the genus Rubus has long been tangled. More than 375 species exist, many of them apomictic microspecies, meaning they reproduce without fertilization and pass their genetics on unchanged. Hybridization between species is common, which historically caused botanists to group many distinct species under single names called species aggregates. Adding to the complexity, the subgenus Rubus can cross with the subgenus Idaeobatus, the raspberry group, producing offspring like the loganberry that blend traits from both lineages.

• 3. A Plant Built to Spread

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  Blackberry stems are called canes, and each individual cane lives for two years. In its first year, a primocane pushes up from the roots, extending anywhere from about 3 to 6 meters along the ground, and grows large palmate compound leaves with 5-7 leaflets. It produces no flowers that year. In its second year, as a floricane, the cane stops lengthening but pushes out lateral buds that develop into flowering branches. Those flowers, each roughly 2 to 3 centimeters across with five white-pink petals, bloom in late spring and early summer. When the fruit ripens, the seeds travel. Mammals including the red fox, American black bear, and Eurasian badger eat the berries and disperse the seeds. Blackberry leaves are food for certain caterpillars, and deer are particularly fond of them. The concealer moth Alabonia geoffrella lays its larvae inside dead blackberry shoots. The plant also spreads mechanically: branches that touch the ground send down new roots, and suckers push up from existing root systems. Unmanaged plants accumulate into dense tangles. The shrubs tolerate poor soils and establish themselves in wasteland, ditches, and roadsides where little else competes. This combination of wildlife dispersal, vegetative spread, and tolerance for marginal land makes blackberries exceptionally difficult to contain once established.

• 4. Invasive and Noxious

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  Rubus armeniacus, called the Himalayan or Armenian blackberry, is classified as a noxious weed and invasive species across much of the Pacific Northwest of Canada and the United States. In urban and suburban parks and woodlands it grows out of control, crowding out native vegetation. Australia, Chile, and New Zealand face similar problems. Two species in particular, Rubus armeniacus and Rubus laciniatus, the evergreen blackberry, have naturalized across southern hemisphere regions and parts of the Americas where they were not originally native. The same qualities that make the plant commercially attractive, its vigor, its abundant fruiting, and its tolerance for poor conditions, are precisely what make it so difficult to eradicate once it escapes cultivation. One acre of blackberry plants can yield up to 20,000 pounds of fruit annually. That productivity is a strength in a managed orchard and a liability in an ecosystem with no natural controls on the plant's expansion. Growers who want to plant blackberries commercially are advised to use certified disease-free stock rather than wild plants, in part because wild plants can carry infections that spread to cultivated varieties.

• 5. Cultivation and the Thornless Revolution

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  The first thornless blackberry variety appeared in 1921, but the berries it produced were largely flavorless, and the breakthrough proved commercially hollow. The real advance came later. Semi-erect, prickle-free blackberries were first developed at the John Innes Centre in Norwich, United Kingdom, and then refined by the United States Department of Agriculture Agricultural Research Service facility in Beltsville, Maryland. From the 1990s into the early 21st century, the USDA program produced cultivars including Triple Crown, Black Diamond, Black Pearl, and Nightfall, a type of marionberry. These varieties combined efficient machine-harvesting with higher yields, larger and firmer fruit, and improved flavor. Thornless cultivars enabled a kind of industrial efficiency that thorny varieties never could. The University of Arkansas contributed a separate line of erect blackberries, including prickly and thornless varieties such as Navaho, Ouachita, Cherokee, Apache, Arapaho, and Kiowa. Arkansas also developed the primocane fruiting types 'Prime-Jim' and 'Prime-Jan', released in 2004, which flower in midsummer and fruit in late summer or fall rather than waiting a full two-year cycle. One cold-hardy outlier stands apart: the 'Illini Hardy' cultivar from the University of Illinois survived down to -24 degrees Fahrenheit during the 1989-1990 winter in Urbana, Illinois, the only variety to do so in that comparative study.

• 6. Mexico, Oregon, and the Global Trade

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  Oregon is the leading commercial blackberry producer in the United States, with 42,600,000 pounds grown on 6,300 acres in 2017. Worldwide, however, Mexico holds the top position, with nearly its entire blackberry crop grown for export to off-season fresh markets in North America and Europe. In 2017, Mexico held 97% of the market share for fresh blackberries imported into the United States, while Chile held 61% of the market share for American imports of frozen blackberries. The Mexican industry was long built on the cultivar 'Brazos', an erect blackberry developed in Texas in 1959. The industry then shifted to the Brazilian cultivar 'Tupy', released in the 1990s. 'Tupy' itself has complex parentage: its parents include the erect blackberry 'Comanche' and a wild Uruguayan blackberry believed to be related to the boysenberry, a hybrid of several Rubus species. By 2018, 'Tupy' had begun falling out of favor in some Mexican growing regions, though it had previously dominated almost the entire Mexican market. To cultivate blackberries in parts of Mexico that lack sufficient winter chilling to trigger natural flower bud development, growers use chemical defoliation and growth regulators to prompt the plants to bloom on schedule. The marionberry, marketed under that name, is itself a carefully constructed cultivar: 'Marion' was selected from seedlings of a cross between 'Chehalem' and 'Olallie', and 'Olallie' is in turn a cross between the loganberry and the youngberry. All three, 'Marion', 'Chehalem', and 'Olallie', came from the USDA-ARS breeding program based at Oregon State University in Corvallis, Oregon.

• 7. Folklore, Medicine, and Deep History

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  The London Pharmacopoeia documented blackberry wine and cordials in 1696, placing the fruit formally within the world of recorded medicine. A document from 1771 described brewing blackberry leaves, stem, and bark as a treatment for stomach ulcers. Greeks, other European peoples, and aboriginal Americans all used blackberry plants in traditional medicine. The fruit, leaves, and stems served another practical purpose: as dye for fabrics and hair. The shrubs themselves, with their sharp thick prickles, were planted as barriers around buildings, crops, and livestock. Folklore in the United Kingdom and Ireland warns against picking blackberries after Old Michaelmas Day, the 11th of October, because the devil or a Púca, a shapeshifting spirit from Celtic tradition, is said to have fouled them. There is a practical truth embedded in that superstition: autumn's wetter and cooler weather genuinely invites mold infection, including Botryotinia, which can make the fruit look unpleasant and may be toxic. In some Christian traditions, the blackberry's deep purple color represents the blood of Jesus, and the bramble has been proposed as the plant used to make the crown of thorns, though hawthorn and the crown of thorns plant have also been suggested. The Haraldskær Woman, whose bog-preserved remains were examined by forensic scientists, carried blackberries in her stomach alongside other foods roughly 2,500 years before any of these documented traditions were written down.