Thornless blackberry. Rubus allegheniensis.This is our all time favorite berry producing plant. Its abundance is unparalleled, producing for several months each year with large juicy berries. This plant is a must have for anyone who is interested in growing lots of sweet treats on their land. The lack of thorns make these plants exceptionally easy to harvest and because they spread by suckers underground, they fill in a patch very quickly at 3 ft spacing. excellent for freezing, canning, fruit leather, jams, jellies, and wines or eaten fresh out of hand.