Rubus argutus 'Hillquist' is a historically and genetically monumental selection of the sawtooth blackberry. Discovered growing wild in Ashland, Virginia, by L.G. Hillquist in the 1940s, this specific diploid germplasm was introduced to agricultural scientists in 1949. While Rubus argutus is broadly native to the eastern and southeastern United States, the 'Hillquist' clone is globally celebrated in plant genetics as the foundation of modern primocane-fruiting (annual-fruiting) blackberry cultivation. Because of its pivotal role in agricultural evolutionary history, its genome was fully sequenced to serve as the definitive chromosome-length reference for the entire blackberry subgenus.

The plant is a thorny, erect deciduous shrub featuring the classic five-lobed or three-lobed serrated leaves and ridged stems characteristic of highbush blackberries. What sets 'Hillquist' apart from traditional wild counterparts is its unique genetic mutation affecting its flowering cycle. In standard wild blackberries, first-year canes (primocanes) remain strictly vegetative, requiring a winter chilling period to morph into reproductive second-year canes (floricanes). 'Hillquist' breaks this biennial bottleneck by initiating flower buds and producing fruit on current-season annual growth, a trait that was exceptionally rare in the Rubus subgenus prior to its discovery.

As a direct food source, the fruit of the wild 'Hillquist' accession is small, slightly tart, and structurally variable—lacking the size and high sugar profiles of modern supermarket berries. However, its value to gastronomy is indirect yet revolutionary. By crossing 'Hillquist' with high-yielding commercial varieties, breeders at the University of Arkansas successfully introgressed its annual-flowering trait into modern elite cultivars (such as the 'Prime-Jim'® and 'Prime-Jan'® series). This single genetic source transformed global blackberry production, allowing farmers to harvest two separate crops on the same plant in a single year, extend the autumn harvest window, and grow blackberries in northern climates where winter freezing normally destroys overwintering canes.