URBANA – It is always recommended to purchase perennials, trees, and shrubs based on your USDA hardiness zone, said University of Illinois horticulture educator Candice Miller.
“But the fact is you can create microclimates in your garden that allow for growth of plants outside the hardiness zone,” she added. “By creating a microclimate, a gardener in northern Illinois for example, which is mostly zone 5, can potentially grow a zone 6 or 7 perennial or shrub in an area where he normally wouldn’t be able to.”
For more detailed information on microclimates, Miller cited the Cornell University Extension website at http://www.gardening.cornell.edu/weather/microcli.html. According to that site, a microclimate is the climate of a small area that is different from the area around it. This area may be warmer or colder, wetter or drier, or more or less prone to frosts.
Microclimates may be rather small, a protected courtyard or raised bed, for example. Or a microclimate may be large, like a band extending several miles inland from a large body of water that moderates temperatures, such as near the Great Lakes.
Your home and the other buildings around your yard can create many small microclimates. Your house absorbs heat during the day and radiates it back at night. If winds are from the northwest, this creates a warmer, more sheltered microclimate on the south and east sides of your house.
“This would be the best area to plant those out-of-zone plants,” Miller said.
Paved areas like patios, driveways, and sidewalks can also absorb heat during the day and re-radiate it at night, moderating night-time soil temperatures and helping to protect from frost.
“You can enjoy earlier blooms by placing plants next to paving or structures that radiate heat as well,” Miller recommended. “A heavy clay soil also acts similar to pavement, trapping heat and moderating temperatures.”
Barriers created with fences, walls, large rocks, or structures can also protect plants from wind and radiate heat, creating sheltered spots.
“Of course, there are always the benefits of adding mulch to the landscape,” Miller said. “Two to three inches of mulch can cool the soil during the summer and help retain moisture, but even more important, several inches of mulch will protect plants from the cold during the winter by moderating the soil temperature.”
“Whatever your choice of method for creating microclimates in your yard, fashioning areas in your landscape to be able to grow some of those more unique plants can be a fun adventure,” Miller said.