If the thought of fighting thorny canes is the only thing between you and a summerlong supply of homegrown blackberries, you're in luck. Thornless blackberries first appeared with the 1911 introduction of Californian Walter Cory's "Cory Thornless." Today, multiple thornless cultivars provide months of gleaming, ebony fruit for preserves, baked goodies and eating straight off the cane. Blackberries flourish in deep, mildly acidic, well-drained sandy loam. Cultivars requiring 200 to 800 hours of temperatures between 32 and 45 degrees Fahrenheit perform well in Mediterranean climates.

Growth Habits

Thornless blackberries grow as erect, semi-erect or trailing plants. Of the three, only semi-erect plants require a trellis or other support. Erect thornless blackberries produce canes from their roots and crowns; trailing and semi-erect cultivar canes sprout from the plants' crowns. Called primocanes in their first year and floricanes when they flower in their second, the canes die back after producing berries.

High-Sugar Cultivars

"Navaho" (R. "Navaho") earns high praise for its exceptionally sweet, late-June-to-August berries. A single, 4- to 5-foot "Navaho" plant bears from 8 to 10 quarts of 1-inch blue-black berries. The fruit's 11.7 percent sugar content is the highest among all University of Arkansas blackberry cultivars. Erect, heat-tolerant "Navaho" grows in full sun in U.S. Department of Agriculture plant hardiness zones 6 through 10. Apache" (R. "Apache") produces heavy, gleaming-black berries on erect, 5- to 8-foot canes. Averaging 10.7 percent sugar solids, the fruit ripens over five weeks beginning in mid-June, after its white, early-summer flowers open against medium-green, compound foliage. Up to 8-feet wide, "Apache" needs a sunny spot with room to spread. It's hardy to USDA zones 5 through 9.

Medium-Sweet Cultivars

"Arapaho" (Rubus "Arapaho"), an erect thornless blackberry, produces white spring flowers and deep-green foliage. Its 8 to 10 quarts of 1- to 2-inch berries, desirable for their extremely tiny seeds, are ready for harvesting in early to mid-June. Spreading from 3 to 5 feet with canes of varying heights, self-pollinating "Arapaho" does well in partial to full sun. Its berries average 9.6 percent sugar content, slightly higher than the larger, 9.5-percent fruit from "Natchez" (R. "Natchez"), another early blackberry. Introduced in 2007, semi-erect "Natchez" stands 4- to 5-feet high and benefits from trellis support. The white-flowering shrub likes full sun, but does best in cool-summer climates in USDA zones 6 through 8.

Pruning Erect Thornless Blackberries

Properly pruning erect thornless cultivars such as "Arapaho," "Apache" and "Navaho" encourages them to send out lateral branches. Trim each year's primocanes back to 3 1/2 feet in late summer or early fall. The cut canes become thicker as laterals emerge from their lower sections, so they support the developing crop without help. Cutting the laterals back to 1 foot in late winter or before they start flowering in early spring encourages larger blackberries.