Landscaping With Snow Removal in Mind
Considering winter weather in your design increases efficiency and public safety.
As one of the people responsible for leading the planning, design and execution of landscape projects on the University of Michigan’s rustic Ann Arbor campus, Marvin Pettway’s focus in the warmer months is to bring the campus alive with a landscape filled with all types of colorful flowers, trees and bushes. While a beautiful end result is always high on his priority list, Pettway is also responsible for keeping campus streets, sidewalks and plazas clean of snow and ice during Michigan’s notoriously harsh winters. As a result, he gives very special consideration to any new landscaping proposal with regards to how the project will affect campus faculty, staff and students, as well as the efforts of his own snow removal team, when winter’s worst hits the campus.
Quick clearing of snow from sidewalks and parking areas is essential to public safety. With that in-mind, following are Pettway’s tips on how to use landscape features effectively as snow storage and melt zones.
Snow melt zones near sidewalks and walkways
Pettway recommends designing plenty of open space on both sides of sidewalks for snow melt zones. Providing at least eight feet of clear space on either side of sidewalks and walkways offers ample area for removal crews to clear them completely. These zones are often called “push zones.” Ideally, push zones should slope gently away from sidewalks to prevent snow melt runoff from creating slick spots when re-freezing occurs. Re-freezing itself is a major concern, but is simply a fact of life in the Midwest, Pettway says. And while it’s impossible to fully eliminate re-frozen ice during snow melt periods, he says that taking terrain slope and available drainage into account when determining push zones can increase pedestrian safety in the winter months. Known problem areas can then be handled with deicing chemicals.
Sidewalk construction materials can be a big factor in the ease of snow removal. Pettway says that natural brick surfaces in particular can be troublesome. Snowplows don’t glide as smoothly on brick surfaces as they do on concrete. The often uneven surface presents many edges for the blade to snag, potentially lifting bricks out of place. That isn’t to say that the world is doomed to the gray concrete sidewalk. In fact, Pettway has become a fan of the recent trend of using poured concrete slabs with stamped brick patterns in plazas and walkways. He likes these much better than real brick due to the material’s consistency under the blade of a snowplow. “Those pressed concrete sections are just so much more hassle-free to clear than real brick; it’s just amazing,” he says.
Bringing the heat
Ice is a dangerous public hazard, and when the thermometer is pegged at zero, there is often no other option than to spread deicing chemicals to eliminate the problem. The single most common deicing chemical in-use today is sodium chloride (or rock salt). Calcium chloride and magnesium chloride are other options that are less corrosive, and cause less skin irritation if contact occurs. They are also more gentle to plants than rock salt. Despite the advantages of calcium chloride and magnesium chloride for plants, the widespread availability and substantial cost advantages of sodium chloride keep it in-use in most snow removal programs across the nation.
Pettway notes that often much of the damage done to plants by deicing chemicals could be avoided by following the application instructions on the product label. “You wouldn’t believe how many people I’ve seen using way too much of a product because they don’t read the label and fail to follow the directions,” he says.
Sodium chloride spray causes two distinct types of damage, or salt injury, to plants. The first is injury to buds from contact with aerial salt spray. The other type is root damage from the sodium chloride soaking into the topsoil, where it is absorbed by the root system. Different species of plants and trees display varying degrees of sensitivity to both types of salt injuries, so it’s important to know what species are salt tolerant and which are not. The sidebar at left (“Examples of salt-tolerant trees and shrubs”) offers examples of several common salt tolerant species of trees and shrubs, while the sidebar on page 10 (“Salt-intolerant trees and shrubs”) gives examples of species to avoid in areas that may see a high concentration of deicing salt in the winter.
“Choose plant type and location carefully around walkways, particularly near steps and building entrances,” Pettway advises. These locations typically see a high concentration of deicing chemicals. Only high-tolerance plants will survive in these environments, unless protected from the salt in a raised planter, or by some other means. Pettway says that he often considers planting annuals in these high-traffic areas.
Parking lot considerations
The slope of a parking lot has much to do with how it handles accumulated snow and it’s runoff. By placing primary push zones at the bottom of a lot whenever possible, runoff flows will be directed away from the lot itself, reducing the chances of someone getting injured on runoff that has refrozen in the lot. Effective drainage for runoff should also be a primary design concern, as heavy runoff unchecked can erode the landscape and cause other types of damage. Ideally, snow melt should be directed to a storm sewer that could properly deal with the volume of water, but in their absence, ample drainage can be achieved by a number of methods. The goal is to let runoff disperse into a large area where ice from re-freezing won’t be a danger. Pettway reminds that anything planted in these runoff areas should be known to be tolerant to salt injuries.
Some landscape designers like to break up the “concrete jungle” effect of large parking lots by planting trees and plants inside the small parking islands within the lot. Pettway advises against this practice however, as he says that it creates additional hazards to avoid while removing snow. Instead, he says that moving plants and trees to the perimeter of the lot, perhaps on a raised perimeter berm, can create good visual area distinction with fewer concerns for snow removal crews in the winter. If you must plant within the islands, Pettway advises to consider planting annuals and using simple ground cover such as cedar chips to lessen the possibility of removal-related damage to the landscape.
Snow removal is a simple fact of life for many of us, but good landscape design can do much to help manage accumulated snowfall and its runoff, and prevent the attrition of trees, shrubs and plants.
Chris Grassman is a freelance writer based in Lincoln, Neb.
EXAMPLES OF SALT-TOLERANT TREES AND SHRUBS
Ash, Birch, Siberian Elm, Silver and Norway Maple, Mulberry, English and White Oak, Russian Olive, Blue, Spruce and Black Walnut
SALT-INTOLERANT TREES AND SHRUBS
Alders; Black Cherry; Hemlock; Black, Red and Sugar Maple; Pin, Red and Scarlet Oak; and White, Red and Scotch Pine
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