In addition to milder winters, Sirman notes that growing seasons are often longer. “This year we had 25-degree [Celcius] temperatures until the end of September, which gives plants a longer period to harden off before winter. However, spring seems to be arriving at the same time—not soon enough!”
But there are also significant disadvantages to enviromental change: altered precipitation rates and weather extremes.
“The downside of climate change for us in the Prairies is the dryness issues,” says Sirman. “Our toughest trees are becoming stressed by droughts and thus weakened, which makes them more susceptible to pests and diseases.” There’s also the issue of less snow cover, necessitating using up valuable water to irrigate plants before freeze-up, “when snow cover used to take care of this naturally,” she adds.
Douglas Justice, associate director, curator of collections, University of British Columbia Botanical Garden, predicts the greatest challenge for gardeners will be the gradual increase in extremes of weather, particularly unexpected frosts at either end of the growing season. “This will hit fruit and vegetable growers especially hard,” says Justice,adding, “In south coastal British Columbia, where deepening summer drought is coupled with excessive winter moisture, the challenge will be to find ornamentals and perennial food crops that tolerate these particular seasonal extremes.”
John Valleau, corporate horticulturist for Valleybrook Gardens in Niagara-on-the-Lake, Ontario, advises, “Grow plants that grow well in your garden.” (In other words, pay attention to your property’s microclimates.) Valleau also cautions against becoming overwhelmed by potential climate change challenges. “There’s no need to do anything drastic and plant entire xeriscapes,” he says. “However, now is the time to reassess your plants and chuck out those that aren’t performing. Be ruthless with the water guzzlers and 10-minute wonders.”
Severe ranges in temperature also affect pests and weeds, says Justice. “Weeds are adapted to tolerating more extremes, including weather, soil conditions, atmospheric pollution, et cetera, and are often readily dispersed—think [how easily] dandelion [seeds travel].”