Gardening: Pay special attention to trees and shrubs

Are there dead branches sticking protruding from the shrub’s greenery? If so, look the plant over carefully looking for abnormal growths and insects but chances are that it is winterkill. Winterkill is a term used when parts of the plant or all of a plant do not make it through the winter. It could be because the temperature dipped too low, for too long or because cold weather came before the plant was ready in the fall. Either way, the dead part of the plant needs to be removed.

Cut off the dead wood next to the first live bud, branch or leaf. In some cases it could be at the ground level.

Shrub roses are not always hardy in Central Alberta. If they tend to winterkill, it is best to wait until they bud out before pruning. That way, one can be sure of leaving living canes and removing all the dead ones.

A common complaint this year is dead canes in the raspberry patch. The majority of varieties of raspberries fruit on second year wood. The canes can be removed in the fall or they usually die over winter. Canes where the tops are dead are the result of winterkill. Primocane raspberries produce fruit on first year wood but usually continue to fruit the second year. Treat the raspberry plants like other shrubs by removing all dead material. Either cut back to ground level or to the first green leaf.

Dead branches in a tree, can be winterkill but it is usually a sign of that the tree is not healthy. It could have a disease or be infested with insects.

Trees with stone fruit, Mayday, chokecherry to name a couple, are susceptible to Black Knot Fungus. A lumpy black growth grows around a branch or limb restricting the travel of nutrients to the area above the fungus. Remove the branch by cutting into healthy wood. Double bag or burn infected wood as soon as possible.

Fireblight is a disease that spreads in moist humid weather. Once a tree becomes infected the leaves turn color and die but continue to hang from the tree. Branches are often black as if they have been scorched by fire. Treatment is the same as for Black knot. Cut the infected part out, bag or burn all infected wood as soon as possible.

The Large aspen tortrix larva a native to Canada, appears early in the season defoliating trees. The caterpillar is known to live primarily in the aspen or balsam poplar forest but also feed on birch, chokecherry and willow.

In the early spring, larva emerge from the ground or crevices in the lower tree trunk, and make their way up the tree where they devour the merging leaf buds. When the larva are ready to pupate they tie and roll leaves around themselves. By the end of June the pupa start to hatch into moths and fly until the end of August at which time they mate and lay eggs (50-450) on the top of leaves. These eggs hatch, feed and go down the tree to overwinter in the cracks, crevasse and occasionally the ground to immerge next spring.

Young larva are yellow or pale green with a black head. As the larva grow and mature they turn very dark green or black.

Infestations are often noticed when the trees are later leafing out than others of the same species. The leaves that are on the tree are rolled with each roll containing a web. Trees that are effected, have the appearance of less leaves than normal at the crown or top of the tree.

Large aspen tortrix infestations will build for two or three years and then disappear usually due to predators or diseases. The insects do not kill the trees but will stunt its growth as the plant must put energy into replacing leaves as opposed to growing new branches

Putting sticking tape such as Tanglefoot around the tree trunk, about a meter from the ground will catch and kill a large number of the larva.

Take a walk around the garden at this time of year paying special attention to the trees and shrubs. A few quick cuts can make a difference to the health and appearance of the trees and shrubs.

Linda Tomlinson in a horticulturalist that lives near Rocky Mountain House. She can be reached at

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