Rubus × 'Ark. 550' is a complex blackberry hybrid developed by the University of Arkansas, resulting from an open pollination of 'Ark. 515', which was a cross between the USDA cultivars 'Thornfree' and 'Darrow'. This lineage was designed to bridge the gap between the logistical ease of thornless genetics and the superior cold hardiness and flavor profiles of traditional thorny brambles. From 'Thornfree', a semi-erect variety, 'Ark. 550' inherited the genetic traits for smooth, thornless canes, which significantly reduces labor and injury during harvest. Conversely, 'Darrow', an erect, thorny variety known for its vigorous growth and exceptional resilience to northern winters, contributed genes for a more upright structure and a deeper, more complex flavor than was typically found in early thornless releases.

The berries produced by 'Ark. 550' are medium-sized and glossy black, characterized by a balanced sweetness. Structurally, the 'Ark. 550' hybrid demonstrates improved fruit firmness compared to 'Thornfree', making it more suitable for fresh consumption and preventing the rapid degradation often seen in older, softer-fruited varieties.