The hybridization of blackberries continues, with new cultivars entering the gardening world on a regular basis. Most cultivars fit into the three main types of blackberry plants: thorny and thorny erect, thornless semi-erect and trailing, which may be thorny or thornless. Most, but not all, blackberry varieties are self-pollinating, also called self-fruitful.
- Thorny and thornless erect blackberries tend to grow up rather than out and are periodically pruned to strengthen the canes and to encourage lateral growth.
- Thornless semi-erect blackberries behave more like shrubs, usually strong enough to stand on their own and having more lateral branches. They are sometimes trimmed and tied to a trellis for additional support.
- Trailing blackberries grow along the ground. The canes may be tied to a trellis or other support to encourage vertical growth, but some trailing blackberries will climb on trees or other structures on their own.
Thorny and Thornless Erect Blackberries
Illini Hardy Blackberry
Illini Hardy (Rubus 'Illini Hardy'), which thrives in U.S. Department of Agriculture plant zones 4 through 6, is an erect, thorny, self-fruiting plant that can stand on its own. It grows to between 4 and 5 feet tall and has a spread of 4 to 5 feet. Clusters of white, 5-petaled flowers arrive in mid to late spring. The edible berries, considered an excellent fruit crop, arrive in mid to late summer, usually in July. The plant loves full sun to partial shade and well-drained soil that is organically rich, moderately moist and slightly acidic.
A thornless, erect self-fruiting blackberry cultivar, the Navaho (Rubus 'Navaho'), USDA zones 6 through 8, produces clusters of small, white, 5-petaled flowers in the spring. The edible fruits follow in mid-summer. Navaho grows to between 4 and 5 feet tall and 4 to 5 feet wide. The plant loves full sun to partial shade. Soil should be well-drained, organically rich and slightly acidic. Though it prefers moist soils, Navaho does not tolerate overly wet soils, particularly clays.
Thornless Semi-Erect Blackberries
The Chester Blackberry
Chester (Rubus fruticosus 'Chester'), USDA zones 5 through 8, is a thornless, semi-erect, free-standing, self-fruiting, shrub-style blackberry with a height and spread of 3 to 5 feet. The pinkish-white, 5-petaled flowers are showy, arriving in early to mid spring. The fruits, considered excellent in quality, mature in mid summer. They are firm, dark, and similar to that found on the Illini Hardy cultivar. Chester prefers well-drained, but moist, organically rich, slightly acidic soils, but is intolerant of wet soils, such as clay.
The Triple Crown
The Triple Crown (Rubus 'Triple Crown'), USDA zones 5 through 8, is a semi-erect, thornless blackberry shrub that produces glossy, firm fruits that mature in summer. The clusters of white flowers are equally showy and bloom in early to mid-spring. The self-fruiting plant grows from 3 to 5 feet tall and has a spread of 3 to 5 feet. They do well in full sun to partial shade and prefer well-drained, moderately moist soil that is organically rich and slightly acidic. Triple Crown is intolerant of wet soils, such as heavy clays.
The wild blackberry (Rubus ursinus), USDA zones 6 through 9, is a trailing, low growing shrub that has slender hooked spines. The large pink or white flowers grow in clusters, blooming in spring and summer. The berries are deep red to a glossy black and are also found through the spring and summer, providing food for wildlife. This wild blackberry thrives in woodland areas, particularly those with gaps due to logging or development. This prolific berry is native to the Pacific Northwest.
Black Diamond Blackberry
Black Diamond (Rubus hybrid), USDA zones 4 through 9, is a thornless, trailing blackberry variety producing medium to large dark purple to black fruits. This prolific plant can grow up to 6 feet tall if trained on a trellis. Unlike the wild blackberry, this one is cultivated for marketing, either as a fresh fruit or in processed foods. Since its seeds are small, it is perfect for jams and preserves. Blooms appear in spring with the fruiting season being early to mid summer.