Connecticut Garden Journal: How to grow and prune blackberries for summer and fall fruit
When I was growing up near my Italian grandfather's farm in Waterbury, me and my cousins would often wander the field edges looking for wild blackberries. We would come home with scratches on our arms, purple juice stains on our clothes and smiles on our faces. They were that good.
Now, we don't have to work so hard to get delicious blackberries. With modern varieties, blackberries are disease free, produce fruit in summer and fall and some have thornless canes. To make life easier, start with purchasing thornless varieties. 'Chester' is a zone 5 variety with good flavor. 'Triple Crown' is a semi-erect variety, hardy to zone 6. 'Prime Ark Freedom' combines summer and fall fruiting with thornless canes. For colder areas, try the summer fruiting, thorny variety 'Illini Hardy'.
Plant blackberries in full to part sun, 3 to 4 feet apart in rows spaced 2 feet apart. Soak the roots and plant in compost amended soil. If you have clay soil, raise the beds by bringing in additional compost and topsoil. Mulch with wood chips to keep weeds away and preserve the soil moisture. Most blackberries will need support so the canes don't flop. Run a 5 foot high wire between two metal or wooden stakes at the ends of the row.
Prune blackberries after they've fruited in summer to remove old canes. In early summer, prune the shoots back by 1 foot to force side branching and more fruiting. For fall bearing varieties, you can also mow down the whole row in fall after fruiting. You'll lose the next summer's crop, but you'll have a bigger fall crop.