Blackberry varieties are classified by the way that they grow and by their appearance (thorny or thornless). Blackberries typically grow best in June in Southern states and July in Northern states according to fruit growers website Pick Your Own. Opinions vary as to whether the thorny blackberries are sweeter than thornless blackberries, but it is apparent that thornless blackberries would pose a lower risk of injury when picking them.
Commonly grown blackberry cultivars include 'Arapaho,' 'Natchez,' 'Apache,' 'Navajo,' 'Ouachita,' 'Hull,' 'Chester' and 'Triple Crown.' The differences among these varieties are the size of the blackberry, the time it takes for the fruit to ripen on the bush, whether or not they have thorns, and if they can grow erect independently or by use of a trellis to help them stand erect. 'Natchez' blackberries, for example, are fairly elongated, have a glossy black finish, and are larger than the other variety of blackberries.
'Arapaho,' 'Natchez,' 'Apache,' 'Navajo' and 'Ouachita' have strong canes and can grow without support, but do not fair well in cold temperatures. Some species of blackberries can grow as high as an average adult while others grow close to the ground. Trailing or semi-trailing blackberry plants such as 'Hull,' 'Chester' and 'Triple Crown,' require a trellis to support the vines of the blackberry plant. Without support these plants would grow close to the ground.
Wild blackberry plants tend to have thorns. While small animals are capable of devouring the fruit on the exterior of the bush, it is difficult for some to get past the thorny branches to reach the fruit inside the bush. Blackberry leaves also resemble poison ivy and many harvesters picking fruit in the wild have become unwilling victims of the itchy plant, warns nature author Steve Brill.
Farmers, scientists and gardeners have created cross pollinated varieties of the wild blackberry and now there are more varieties of thornless plants than those with thorns--'Kiowa' and 'Brazo' for instance. These thornless plants are ideal for picking fruit for both young and old.