Raspberry plants are relatively easy to grow. They are also hardy and productive in most parts of Iowa. If given good care, a 100-foot-long row of red raspberries can produce 100 to 150 pints of fruit. Proper training and trellising of raspberry plants help insure a good fruit crop.
Red raspberry plants should be maintained in a 1- to 2-foot-wide hedgerow. Remove any suckers that grow outside the hedgerow with a rototiller or spade. Do not allow red raspberries to develop into a wide, solid patch. Cultural practices become extremely difficult and crop yields are reduced when red raspberries grow into a large, dense thicket. Black and purple raspberries grow in clumps. The new shoots (primocanes) of black and purple raspberries need to be pinched when they reach a height of 36 to 48 inches. If allowed to grow unpinched, the canes grow long and fall onto the ground. These canes often root and produce new plants where the tips touch the ground. Tip-layered plants crowd the existing planting and make cultural practices more difficult. Any tip-layered plants should be removed.
Red, black, and purple raspberries can be supported with a trellis. A trellis keeps the canes off the ground. This is especially important when the plants are laden with fruit. The fruit on trellised plants are cleaner and easier to pick. A trellis also reduces crop losses due to storms and facilitates other cultural practices.
There are several different trellis systems. A two-wire permanent trellis is commonly used for raspberries in the home garden. Its construction requires wooden posts, No.12 or 14 galvanized wire, and 2- by 4-inch lumber. The wooden posts should be 3 to 5 inches in diameter and 6 to 8 feet long. Posts should be set 2 to 3 feet into the ground and spaced 15 to 20 feet apart. Near the top of each post, nail or bolt a 24- to 30-inch-long crosspiece. Then run or attach the galvanized wire through the ends of each crosspiece and down the entire length of the row. The two wires should be spaced about 2 feet apart and positioned 3 to 4 feet above the ground.
A temporary trellis may be constructed of posts and twine. Space the posts about 15 feet apart and support the canes with twine. This temporary structure is most suitable for fall-bearing red raspberries grown exclusively for the fall crop.
If utilizing a permanent trellis system, carefully pull and tie the canes of black, purple, summer-bearing red raspberries, and fall-bearing red raspberries (when grown for 2 crops) to the support wires after pruning in the spring. Use twine or cloth strips to tie the canes to the wires. Tying the canes to the trellis wires allows for better light penetration into the center of the row and promotes stronger shoot development. Also, harvesting fruit is easier because the tied canes are more accessible.
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