Building trellises for trailing blackberry plants is quite simple.
If you are planting trailing varieties of blackberry it will be necessary to provide support to keep the canes off the ground. Blackberry trellises are simple and inexpensive to build.
Here's some simple step-by-step instructions:
Step 1 - Sink two 8-foot pressure treated 4x4 posts about 3 feet deep in the ground at anywhere from 10 to 20 feet apart. In sandy soil you'll need to add a quick-setting mortar mix to anchor the posts. In more dense soils just tamp the dirt down good around the post.
Step 2 - Make two marks on each post, one at 2.5 feet above the ground and the other at 4.5 feet above the ground.
Step 3 - Using staples or u-nails, attach 9-guage coated wire at the posts where marked. Before attaching, wrap the wire one or two times around the post. Make wire as tight as possible. You're done!
During the first year it is not necessary to train the blackberry canes to the trellis. Starting the second year tie the canes to the trellis. Loosely tie the canes to the wire as they develop. The best time to do this is before the buds start to swell in early spring.
Spacing Plants
How far apart you space plants will depend on the type of blackberry. It's best to follow spacing instructions on the plant label/tag or consult with your local nursery and garden center professional or Extension agent.
There are two types of blackberries: erect, and trailing, and there are many varieties available in both of these types. Erect varieties have stiff canes that are upright and arching. They can be grown with or without a trellis as a hedge or shrub border and, in general, should be spaced 2 to 4 feet apart, depending on the variety. Trailing blackberries have flexible canes that must be tied to a trellis or fence so they don't flop to and lay on the ground. In general, these should be spaced 5 to 6 feet apart.
