by Don Janssen, Extension Educator
Many times the difference between success and failure with some plants is dependent on a little known and sometimes misunderstood factor called microclimate.
A microclimate is a variation in temperature, humidity or wind velocity due to differences in elevation, direction of slope, soil, vegetation or some other factor. An area might be prone to late spring or early fall frosts, warm up sooner or dry out faster in the spring, or be the last place in your yard where the soil freezes in winter.
When you avoid planting frost-susceptible plants in a low spot in your yard, you are recognizing the importance of microclimates in gardening and using that knowledge to increase your chances of gardening success. Likewise, when you put a bird feeder up where it will be sheltered from winter winds, you make it more attractive to backyard birds and so more enjoyable.
Examples of planting advice based on knowledge of microclimates abound. Planting fruit crops on high ground and locating mildew-plagued plants such as lilacs and zinnias where good air circulation will help dry their foliage are two. Another is the recommendation to plant evergreens such as holly and rhododendron where they won't be exposed to drying winter sun and wind.
Microclimates sometimes allow gardeners to succeed with plants that are technically out of their natural range. A plant that should not survive a typical winter may grow for many years in a sheltered spot before an unusually harsh winter kills it. Sometimes, however, a microclimate that provides milder conditions is not appropriate. The best example is probably spring-flowering bulbs planted too near a building, where heat radiating from the basement prevents the soil from cooling down enough to provide the chilling treatment the bulbs require.
Gardeners aren't the only ones to take advantage of microclimates -- they are often surprised to find that moles were active in their gardens all winter. But it makes sense, if you think about it. If the soil is high in organic matter or heavily mulched, it will be slow to freeze, and insects and earthworms will be active there long after the lawn is frozen. Add an insulating layer of snow that persists all winter, and you have a microclimate that makes the garden much more hospitable than other parts of the landscape.
For a quick lesson in microclimates, go outdoors on a brisk, breezy winter day and compare your comfort level on the leeward side of a thick evergreen hedge and a windswept hilltop. Watch where the snow melts first and where the frost lingers in the spring, and then you can use your awareness of microclimates to your garden's advantage.
University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office