Thornless blackberries can be grown in warmer areas of Pennsylvania. Some varieties are trailing and will need a trellis for support. The following varieties are recommended:
Apache: A new variety with improved size and yields over Arapaho and Navaho. Winter-hardiness is still a concern.
Arapaho: The earliest thornless blackberry. Medium-sized fruit with small seeds. Fairly erect in growth habit.
Chester: Ripens relatively late in the season. One of the most commonly grown thornless blackberries, in part due to good-quality fruit. Has a trailing growth habit.
Navaho: Relatively late fruiting. Fruit is medium sized and has good flavor. Growth habit is erect.
Ouachita: A very recent release. Has produced large fruit and high yields in other areas of the country but is untested in Pennsylvania.
Triple Crown: Very productive. Fruit is large and sweeter than other thornless blackberry varieties. Growth habit is intermediate between erect and trailing types.