Hey there, time traveller!
This article was published 25/4/2014 (889 days ago), so information in it may no longer be current.
Feeling a bit ravaged by the long winter? Imagine spending all of it outdoors these past several months. Given all that trees and shrubs must contend with from Mother Nature -- extreme temperatures, high winds, storms, pest infestations -- they can be forgiven for not always looking their best.
Not all trees and shrubs in the landscape are beautiful. In fact, some are downright eyesores.
But when that happens, it's probably not the fault of the plant. People can be a tree or shrub's main adversary, shortening its life or altering its appearance for the worse due to bad practices. Or sometimes, simply not making the right choice can have a lasting impact on the landscape.
Perhaps the best example of a tree that has gone from handsome to unsightly is the Schubert chokecherry, which dots so many boulevards and landscapes throughout our city. Selected for its strong ornamental value, spring flowering and purple foliage later in the season, the poor Schubert is afflicted with black knot fungus, sometimes affecting the overwhelming majority of its branches.
In hindsight, planting so many of them at the same time probably wasn't a good idea. When the disease is present, though, the problem is compounded by improper pruning practices. Since black knot fungus is a systemic disease, the best time of year to prune the Schubert is in early April when the ground is still frozen and active growth has not yet begun.
Gerry Engel, an ISA-certified arborist and owner of Tree Life Services, has experienced good success with Schubert chokecherries by pruning only in early spring before the wood of the tree begins to soften. "What we are seeing over the last decade and especially in the past three years with drought conditions," said Engel, "is that the disease has really accelerated."
Engel isn't giving up on the Schubert and is experimenting with tree pollarding. A widespread pruning technique that is practiced in Europe but lesser-known in North America, pollarding was once used to harvest wood. Today, it is used to control size and involves heading back shoots to approximately the same level each year. Thus far, Engel's experience has been the first year's annual growth has been free of the black knot fungus, and he will continue to monitor the progress.
Engel also promotes proper soil care, particularly through the use of mulch and compost for improved microbial activity.
"A common theme in the springtime is to fertilize," said Engel who does not use any synthetic fertilizers nor recommends them to his clients. An exception might be in the use of rock or river stone around the base of a tree, which disrupts the natural flow of nutrition to the tree. "A combination of rock and turf can do a good job at conserving water and improving water filtration; however, natural mulch decomposes over time and builds soil structure," advises Engel.
In addition to the importance of diversity and proper soil care, another factor to consider when choosing a plant for your landscape is hardiness.
Gerry Aubin, owner of Aubin Nurseries, a family-owned business in Carman that is situated on 500 acres, says not all tree and shrub varieties will thrive in every site.
A strong proponent of selecting proven performers over new and untried introductions, Aubin recognizes how hard it is to not be persuaded by the aggressive marketing of the newest varieties of trees and shrubs.
Consider the mature size of any tree or shrub you are purchasing. "Everyone is looking for smaller-sized trees," acknowledges Aubin. Shogun Japanese tree lilac (formerly known as Durand Japanese tree lilac) is a narrow upright specimen, hardy to zone 2, with a mature height of 20 feet and grows to a width of 13 feet. With large panicles of fragrant, long-lasting creamy-white flowers in early summer, this ornamental specimen, developed by Rick Durand, will perform well in a full sun location without overwhelming your landscape.
In love with purple leafed trees? Aubin highly recommends the Mary Liss pincherry. A stunning tree with maroon red foliage and pink blossoms, its upright, broadly oval form is accented by light grey bark and has demonstrated hardiness.
Along with hardiness, disease resistance is very important. Some of the flowering crab apples, for example, begin defoliating in July and August, dropping unsightly leaves that are marred by black spot and scab. Courageous Flowering Crab is a small, narrow crab apple with uniform shape and excellent disease resistance.
"What I like about it," describes Aubin, "is that the branching is absolutely clean. I haven't seen any disease in the foliage at all."
Maintaining the proper form of your trees is accomplished by pruning. In a typical spring, most gardeners would have completed all of their pruning tasks in early April. Is there reason to be concerned with the late start?
Matt Vinet, a certified ISA arborist, chuckles when he recalls visits to his clients earlier this month. In many cases, Vinet, who manages the Winnipeg office of Green Drop Lawn and Tree Care encountered snow cover that made viewing inaccessible and pruning impossible. "If pruning is delayed too long," said Vinet, "the flowering period can be affected." A rule of thumb is to prune early flowering plants like lilacs and fruit trees after they have finished flowering. For most plants, though, the preferred time to prune is during the dormant season, although light pruning during the growing season will not harm plants.
Pruning of elm trees, however, is governed by law. "Do not prune elms between April 1 and July 31," advises Kerienne Lafrance, executive director of Trees Winnipeg (Coalition to Save the Elms). If you have any questions about your elm tree, visit www.savetheelms.mb.ca or phone 204-832-7188. Trees Winnipeg has extended its mandate to protect and preserve the urban forest as a whole and are happy to answer any questions you may have about the trees on your property.
"This is a do-it-yourself era," said Vinet. "If you are building a deck and something goes really wrong, you can start over again. In the case of a living thing like a tree, the damage can be permanent." Sometimes a pruning task is better left to a trained professional who also has the skill and experience to tackle dangerous jobs. Whatever the task, the decision to hire an arborist allows for the opportunity to assess your landscape and develop a health-care plan that includes pruning as well as insect and disease management.
Is there a silver lining to the weeks and months of continuously freezing temperatures where damaging pests are concerned? Taz Stuart, former City of Winnipeg entomologist now serves as the director of technical operations for Poulin's Pest Control.
"Normally at this time of year," said Stuart, "we would be seeing the female wingless cankerworms crawling up trees, but with the ground still frozen, we aren't seeing any activity yet."
Can we hope the cold temperatures eradicated cankerworm populations? "It's survival of the fittest," said Stuart. "There may be some natural die-off of the weaker eggs, but it doesn't mean you are going to have total decimation of the population."
Perhaps less reassuring, too, is the concern forest tent caterpillars may be ready to increase their numbers as part of their natural eight-year cycle. We will have to wait until mid-June before we will know if the long, cold winter had any effect on their population.
Heavy snowfall is a precursor to heavy vole damage, an increasing concern in terms of both turf and tree damage. Active throughout the entire winter under an insulating blanket of snow, voles gnaw on the bark at the base of trees, which can cause a serious injury called girdling, affecting healthy growth through the restriction of water and nutrient movement.
A non-chemical control option you can try this spring includes cutting the grass to a short height to reduce the opportunity for voles to create their characteristic pathways in the grass. And if possible, keep snow at minimal levels next winter. Mother Nature may have to help with that one.