Blackberry Cage . Get it as soon as wed, apr 27. The wire should be placed at 2, 3, 4, and 5. Blackberry bush in a pot. Used a tomato cage for it to climb. Lots of from www.pinterest.com If you are creating several rows, dig holes 6'12' apart. My bottom eyelet is 12 inches off the ground and the top one is 3 inches from the top. If a grower has more than one row of blackberries, the rows should be spaced a minimum of 12 feet apart.