How to Make a Blackberry Trellis

Dig a hole 3 feet deep and big enough in circumference to easily accept the fence post. Dig a second hole 20 feet from this hole. These holes will define the outermost ends of your trellis.

Dig out the bottom of each hole with a spade. Make the bottom one foot of the hole about twice the circumference of the top of the hole, creating a bulb shape at the bottom.

Pour or shovel a four-inch layer of crushed rock into each hole. Settle and firm the gravel by tamping it down with one of the fence posts.

Place one of the posts into the hole. Level the post, checking two adjacent sides of the post. Prop the post in level position using the scrap lumber lengths as supports, nailing them into the post to secure them temporarily. Repeat with the second hole and fence post.

Prepare the quick-setting concrete as indicated on the package.

Pour or shovel the concrete into each post hole, filling it up to one foot below the surface of the ground. Allow the concrete to dry according to the specifications on the package.

When the concrete is dry, shovel dirt from the hole back in to fill it up to the surface of the ground, firming the dirt around the fence post as you go. Remove the temporary supports.

Measure and mark each post to indicate the desired height of the wire span. Using a tape measure and pencil, mark a point on each post that is 30 inches from the ground if you are building a trellis for erect blackberries, or 3 feet from the ground for trailing blackberries.

Staple the end of the wire securely to one post at the penciled mark. Keeping the wire taut, span the distance between the two fence posts, and securely staple the wire to the opposite post at the pencil mark. Cut off the excess wire.
For a trailing blackberry trellis, staple both ends of another length of wire to the same side of each post just under the top of the post. Cut off any excess wire.