From the Ground Up: Take advantage of your own microclimates

LINN COUNTY - We've had some pretty cold temps already this fall, which makes me think back to last winter and wonder why some plants that I thought were hardy (Autumn Joy clematis) didn't make it, and others that aren't so hardy (some varieties of heuchera) did make it through the severe cold. This phenomenon may have something to do with microclimates and you may have them in your yard.

The U.S. Department of Agriculture calls microclimates 'fine-scale climate variations” over an area. A microclimate can be a small heat island around blacktop or concrete or a cool spot created by a small hill or valley.

Individual gardens can have very localized microclimates, influenced by shelter or exposure. The USDA states that 'No hardiness zone map can take the place of the detailed knowledge that gardeners pick up about their own gardens through hands-on experience.” No kidding.

For example, a hollyhock planted by a white wooden fence will grow differently than one next to a brown fence. The white fence will radiate more heat. Another example is a stream that creates a microclimate of damper air and soil, encouraging certain plants to thrive near it.

Gardeners can take advantage of microclimates to improve a plant's chances for winter hardiness, which usually means creating a warmer spot. The Japanese maple growing in a sunny sheltered corner of my front yard is a perfect microclimate plant.

Some tips about using microclimates to your gardening advantage:

l Focus on structures, like your house or a garden shed, that absorb the day's heat and radiate it back at night, or block chilling winds, creating warmer, more sheltered microclimates on the south and east sides. Also fences, walls and large rocks can protect plants from wind and radiate heat, creating sheltered spots. These structures can also cause cold air to pool, creating the possibility of localized frost damage on near-freezing nights.

l Focus on hard surfaces, like driveways, sidewalks, patios, paths that absorb heat and reradiate it at night, moderating night temperatures.

l Focus on trees and larger plantings, particularly their height, spread and orientation. Tall trees can create microclimates by shading and protecting plants. On the other hand, they can also prevent rain from reaching the ground.

l Focus on season extenders to add productive days to the growing season. Raised beds, row covers, and mulches can extend the season, allow air circulation, and warm or cool the soil. You can extend he growing season of vegetables by placing them in warm sunny spots, or in containers.

Interesting fact, Thomas Jefferson studied microclimates, experimenting with growing many different varieties of fruit on the warmer, southeast side of his Monticello home, where he successfully grew fruits from zone 9 on his land which was zone 7a.

' Jean Murray is a Linn County Master Gardener.