Pruning season awakens just before spring
Raspberries can grow into a tangled mess and produce poorly if they are not pruned properly. Prune fall-fruiting raspberries (that fruit between August and October) back to the ground now to produce one crop of fruit.
Most fall-fruiting varieties are primocanes that produce fruit in their first year of growth. Cut the old canes as close to the ground as possible so buds will break from below the surface of the soil. New canes will grow and set fruit later in the year. If the canes are not cut low enough, fruiting laterals may form on any remaining cane portion. These fruiting laterals will not be as healthy.
Summer fruiting varieties are floricanes, which fruit in the second year of growth and thus require different pruning techniques.
• A good time to prune fruit trees is in late February or early March, before the buds begin to swell. The branching habits are easy to see, and the weather is generally more conducive to outdoor work.
Avoid working in the rain or walking over the root zone of a tree when the soil is soft and wet.
Disinfect your tools with Lysol disinfectant or a solution of 9 parts water to 1 part bleach after completing each tree and after each pruning cut if there are diseased branches present.
A general goal of pruning a fruit tree is to thin the canopy of the tree in order to increase sunlight and improve air circulation, which in turn will increase fruit production and help reduce diseases.
First, remove all dead or diseased branches. These will be easy to spot because the wood is generally darker than healthy wood. Then thin the canopy by first focusing on pruning out branches that grow toward the center of the tree rather than out away from the center.
When possible, prune out branches that have narrow, V-shaped crotch angles, as they are more susceptible to breaking under pressure than wider, U-shaped crotch angles. The angle formed by a V-shaped crotch is less than 30 degrees. Prune out all suckers that arise from the ground next to the main trunk or grow vertically from lateral branches. Try to encourage the growth of lateral, fruit-producing branches and discourage upright vertical growth that produces little fruit.
Finally, prune out branches that rub against each other or are growing over a walkway, driveway or doorway.
• Tim Johnson is director of horticulture at Chicago Botanic Garden, chicagobotanic.org.