Rubus × 'Ark. 631' is a complex blackberry hybrid developed by the University of Arkansas breeding program, resulting from the cross between their experimental selection 'Ark. 550' and their established cultivar 'Cherokee'. This lineage was designed to enhance fruit firmness and plant resilience; the 'Cherokee' parent—a 1974 release—contributed vigorous, thorny, erect canes and high productivity, while the 'Ark. 550' line was utilized to refine the berry's post-harvest stability and flavor profile. This hybrid serves as a vital genetic bridge in the development of modern "shipping-quality" blackberries, characterized by its ability to maintain drupelet integrity after being refrigerated.

The fruit of 'Ark. 631' is notable for its large size and high gloss, inheriting the deep black pigmentation characteristic of its 'Cherokee' ancestry. Because it is a "thorny" selection in the erect breeding line, it possesses a high concentration of lignified structural tissues in its stems, which supports a heavy crop load without bending.