Most people think red when they think of raspberries, but there are red, yellow, purple and black raspberries. Yellow raspberries are a mutation of red raspberries (Rubus ideaus) and purple raspberries are a hybrid of red and black raspberries (Rubus occidentalis). Traditionally raspberry plants produced berries on 2-year-old wood (floricane) in early summer. In 1969, the first everbearing variety was released. Everbearing varieties can produce berries on 1-year-old wood in late summer and fall. Raspberries are hardy in U.S. Department of Agriculture plant hardiness zones 3 through 9. Shop for varieties that have been proven to do well in your area.
Summer-Bearing Red and Yellow Raspberries
Traditional floricane or summer-bearing raspberries produce fruit on wood that grew the previous year. The plants flower in the spring on 2-year-old wood, berries mature in June, then new canes grow for the rest of the summer. Remove canes at the ground after they produce fruit so that they do not form an unproductive, impenetrable thicket. In areas with cold winters young canes often suffer freeze damage during the winter.
Everbearing Red Raspberries
Canes on everbearing, or primocane, varieties start growing in early spring and produce a crop of raspberries on new wood at the end of the summer. These same canes will produce a smaller crop the next June if they remain on the plant. Generally, the canes are mowed off after the fruit is harvested because this eliminates freeze damage and allows all of the plant's energy to go into producing a large fall crop.
Black and Purple Raspberries
Black and purple raspberries produce fruit on branches that grow out of the sides of old canes. These side branches produce fruit in their second year. In summer remove fruit-producing canes after harvesting the fruit and cut off new canes 3 to 4 feet above the ground to encourage them to form branches. In late winter, thin the canes, leaving four to six of the strongest canes per foot. Cut back the side branches. Black and purple raspberries are generally less cold hardy than red raspberries.
Planting and Trellising Systems
Space red and yellow raspberries 2 to 3 feet apart in the row. Summer-bearing varieties are often trellised. Everbearing varieties grown in a wide hedgerow will support each other, or you can provide a temporary trellis that can be removed for mowing. Black and purple varieties should be spaced 3 to 4 feet apart to allow room for the side branches. Trellis black raspberries on a low trellis. Purple varieties are sturdier and will support themselves.
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