Thornless blackberries, just like traditional blackberry plants, are members of the rose family of perennial bramble plants. Like traditional blackberries, thornless blackberries come in trailing, semi-erect and erect cultivars. The only differences between thornless and traditional blackberries are that thornless varieties tend to have sweeter, juicier, bigger fruits and are more cold hardy. All blackberries are high in anti-oxidants, contain anti-carcinogenic nutrients, and are high in vitamins, A,C, E and K as well as foliate, magnesium, calcium and potassium.
Choose a sunny site with good drainage (the southern side of a slope works well), and a pH between 5.5 and 7.0 with a pH of 6.0 being ideal.
Blackberries are shallow rooted brambles. Plant them just deep enough to cover the roots. Space upright brambles 4 feet apart. Trailing brambles need to be planted at least 5 feet apart. If you are planting in rows, leave at least 10 feet between rows.
Trim any broken or dead canes after planting. For yearly pruning, cut canes that have borne fruit to the ground after harvest. Trim back the rest of the canes (the first year non-fruiting) to 36 inches. Trim lateral branches to 12 inches.
Trellising trailing thornless blackberries prevents disease and will increase production. Choose the strongest 3 first year and second year canes and tie them to the trellis in a fan shape. Use flexible plant ties or string to loosely tie the canes.
Fertilize your canes yearly in late winter or early spring with a shovel full of well-rotted manure or compost per plant or use a 10-10-10 fertilizer and follow package directions.
To keep your blackberry patch weed free use 2 to 3 inches of mulch around each plant. To fertilize, just pull the mulch away from the blackberry plant, apply the fertilizer and re-mulch.
Thornless blackberries will need at least 2 inches of water a week during the growing season (April/May to September/October) for optimum berry production.