March 2, 2011

Ask the ISU Extension Garden Experts

Pruning red raspberries

Q. What is the proper way to prune ‘Latham’ red raspberries in late winter?

A. ‘Latham’ is a summer-bearing variety of red raspberry. Other popular summer-bearing red raspberry varieties include ‘Boyne,’ ‘Killarney,’ and ‘Newburgh.’ All summer-bearing red raspberries should be pruned in the same manner. In March or early April, remove all weak, diseased and damaged canes at ground level. Leave the most vigorous canes, those approximately one-fourth inch in diameter when measured 30 inches from the ground. After thinning, remaining canes should be spaced about six inches apart. Also, prune out the tips of the canes that have died due to winter injury. Cut back to live tissue. If the canes have suffered little winter dieback, remove the top one-fourth of the canes. Cane-tip removal or “heading-back” prevents the canes from becoming top heavy and bending under the weight of the crop. To obtain maximum yields, red raspberries should be confined to a one- to two-foot-wide hedgerow. Shoots growing beyond the one- to two-foot-wide hedgerow should be dug up and destroyed using a rototiller or spade.

Protect serviceberries from rabbits

Q. I intend to plant several serviceberries this spring. Will I need to protect them against rabbits next winter?

A. Rabbits are quite fond of serviceberries (Amelanchier species). If not protected, plants are likely to be damaged or destroyed by rabbits during the winter months. Fencing (hardware cloth or chicken wire) is the best way to protect serviceberries and other woody plants from rabbits. The fencing material should stand three feet above the ground. (Rabbits eventually may be able to reach or climb over the tops of two-foot-tall fences in winters with frequent snows.)
Pruning shade trees

Q. When is the best time to prune shade trees?

A. February through March is generally regarded as the best time to prune most deciduous trees. The absence of foliage at this time of year gives the individual a clear view of the tree and allows the selection and removal of appropriate branches. Also, the walling-off or compartmentalization of wounds occurs most rapidly just prior to the onset of growth in spring. Oaks are an exception. The winter months – December, January and February – are the best time to prune oak trees. Large amounts of sap often flow from pruning cuts on maple, birch and elm when pruned in late winter. However, the loss of sap doesn’t harm the trees. The trees won’t “bleed” to death. Eventually the flow of sap will slow and stop.

To ask the ISU Extension garden experts questions, call the Hortline at (515) 294-3108, Monday-Friday from 10 a.m. to noon and 1 – 4:30 p.m., or e-mail