The loganberry is an hexaploid hybrid produced from crossing an octaploid blackberry

Blackberry

The blackberry is an edible fruit produced by any of several species in the Rubus genus of the Rosaceae family. The fruit is not a true berry; botanically it is termed an aggregate fruit, composed of small drupelets. The plants typically have biennial canes and perennial roots. Blackberries and...

 and a diploid red raspberry

Rubus idaeus

Rubus idaeus is a red-fruited species of Rubus native to Europe and northern Asia and commonly cultivated in other temperate regions. A closely related plant in North America, sometimes regarded as the variety Rubus idaeus var...

. The plant and the fruit resemble the blackberry more than the raspberry, but the fruit colour is a dark red, rather than black. Loganberries are cultivated commercially and by gardeners.
The loganberry was derived from a cross between Rubus idaeus 'Red Antwerp'

Rubus idaeus

Rubus idaeus is a red-fruited species of Rubus native to Europe and northern Asia and commonly cultivated in other temperate regions. A closely related plant in North America, sometimes regarded as the variety Rubus idaeus var...

 and Rubus ursinus

Rubus ursinus

Rubus ursinus is a species of blackberry or dewberry known by the common names California blackberry/dewberry, Douglas berry, and Pacific blackberry/dewberry. It is native to western North America. This is a wide, spreading shrub or vine-bearing bush with prickly branches that can tip layer to...

(R. vitifolius) 'Aughinbaugh'.