Landscaping after heavy snowfall
May 19, 2008
Mending mechanical damage
When the snow finally melts and you walk through your yard, take careful note of the devastation to those plants in areas where deep snow has accumulated. We’re coming out of a year of above-normal snowfall, and as a result, considerable mechanical damage to branches can result where snow accumulates, as on the north and east sides of a house, and where snowplows and snowthrowers remove snow from roads, driveways and sidewalks. This can be ameliorated next year by changing your behavior (i.e. pushing snow on turf areas rather than on woody trees and shrubs). As snow depth increases, so does the density. That fluffy 7-percent density snow that fell out of the sky last winter is 50-percent density or greater by the end of winter. The weight of this denser snow pulls down on the lower branches and usually causes the branch to break at the branch collar. If the broken branch is attached by a strip of bark, it should be pruned to avoid further mechanical damage.
Relandscaping your boundaries
If you’re trying to landscape areas along the side of your street and driveway where snow accumulates as a result of shoveling or plowing, your best bet is to plant herbaceous plants, plants that die back to the rootcrown each year rather than woody trees and shrubs. Ornamental grasses, which are capable of growing inches a day due to their extensive fibrous root system, are an excellent choice in these tough sites. However they may not do well on the north side of your house due to their low shade tolerance. Some of my favorites include the native Great Basin wildrye and blue lymegrass as well as apt, drought tolerant non-native species like tall wheatgrass, blue oatgrass and "Karl Foerster" feathergrass. These can be combined with fast-growing annuals like sunflower to provide privacy. Some good perennials to use include daylillies and German irises that have a tuberous or rhizomatous rootstock.
Planting resilient shrubs
If you’re a glutton for punishment, like me, and you still want to establish woody trees and shrubs in these difficult areas, some are more resilient to snow damage than others. As a general rule, try to use shrubs that are rubbery and flexible or species that have evolved in these deep snow environs. Some examples include our native rubber rabbitbrush, the snowberry and the Potentilla. Low-growth forms like spreading cotoneaster will also work, but low-growing junipers should be avoided in these areas because of their susceptibility to snow mold, which is toxic to foliage. Keep in mind that areas accumulating deep snowpacks are the last to melt out in the spring and also tend to grow snow mold. Some of our native conifers like bristlecone pine and limber pine work well in deep snowpack areas, but they may develop some snow mold on their lower branches. Another characteristic of snow resiliency is multi-stemmed growth form and/or those species that reproduce by suckering. Multi-stemmed plants aren’t putting all of its energy into a strong central leader; therefore you may lose some branches to mechanical damage but more branches will sprout to replace those that are lost. Recommended species include our native river birch and red-stemmed dogwood. Shrub species to avoid in these deep snow areas include those with soft wood and/or poor branch structure, like the ginnala maple, "Cistena" flowering plum, smooth sumac and staghorn sumac.
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Choosing strong trees
When it comes to planting trees in these difficult deep snowpack sites, small trees won’t work. You need a tree that has a canopy that is higher than the maximum snowpack depth. Good tree choices include Colorado blue spruce, Douglas fir, subalpine-fir and white fir. Pines like Austrian pine and the Swiss mountain pine or mugo pine should be avoided because of their weak, whorled branch structure. Also, fast growing, weak-wooded species like those in the willow family – e.g. aspen, cottonwood and willows – should be avoided in these tough sites.
Keith B. Clapier, ISA Certified Arborist #UT-0034A