How to Raise Thornless Blackberries

Plant blackberry canes in early spring, when the frost is off the ground. This gives the vines time to grow and establish before the following winter.

Choose a planting spot that gets full sun for at least eight hours every day, as blackberries won't bloom or bear fruit in the shade. Make sure that your site gets complete drainage, to keep blackberries out of standing water. Avoid locations where tomatoes, peanuts, cucumbers, roses or pumpkins grew, since those plants can leave diseases in the soil.

Dig a combination of half organic compost and half quick-draining soil or sand into the top 4 inches of soil. Although thornless blackberries can grow in poor soil, they require an amendment to increase the drainage of the soil. Organic matter will increase soil nutrients and lead to quicker and healthier growth.

Plant thornless blackberries like Arapaho, Navaho, Apache, Ouachita and Boysenberry in holes that are as deep and twice as wide as their root balls. Space plants 2 feet apart on the row and leave six to seven feet between rows. Put a trellis behind the blackberries to provide support as they grow. Make sure that each blackberry bush has easy access to the trellis.

Cut the canes down to 6 inches after planting to promote branching and new growth. Spread 2 to 3 inches of organic mulch around each plant to maintain soil warmth and moisture as the new blackberries grow. Put the bushes on a schedule of 2 inches of water a week. Replenish the mulch as it breaks down.

Feed thornless blackberries every spring with 8-8-8 fertilizer to promote growth and blooming. Look for the first fruit in the blackberries' second year.