Microclimates: A Guide to Mini-Zones

Paying attention to the microclimates in your garden can extend growing season as well as plant choice...

Caryopteris clandonensis 'Dark Knight'
Item # 30715 		Caryopteris clandonensis 'Dark Knight'
Blue Mist Spirea

each $8.29
3 or more $7.99
Aegopodium podagraria ‘Variegatum’
Item # 10910 		Aegopodium podagraria ‘Variegatum’
Variegated Bishop’s Weed

each $4.99
3 to 6 $4.79
7 or more $4.59
Caryopteris x clandonensis 'Longwood Blue'
Item # 30720 		Caryopteris x clandonensis 'Longwood Blue'
Blue Mist Spirea

each $8.29
3 to 6 $7.99
7 or more $7.79
  • Topic: Plant Selection
  • Author: Cindy Bellinger
  • Keywords: weather, microclimates, zones, berm, climate, site, location, Site Solutions
  • Date: November 2003

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Ever notice that bulbs along a south facing wall are the first to come up in the spring? Or that the locust tree here always loses its branches whereas the one over there never does?

Microclimates, those small areas of varying temperature and weather patterns, are often the key to sustaining a wide variety of plants in any garden.

Some landscape designers recommend living in a place for a year before planting a garden. This way you can make note in the shifts of light and wind, sun and shade throughout the seasons.

When I moved into my place, I was too eager to get a garden going so gave no time to learning the idiosyncrasies around the yard. I first toured the place late morning in spring. Lots of sun flooded the northeast portion of the yard, and without even thinking, I planted a succulent ground cover that’s barely been able to hold its own.

Climate is the basic factor for diversity among plants and animals everywhere. The weather variables that define any climate are temperature, wind, moisture and humidity. Working within these is the interplay of sun and shade.

It’s rare to find a garden that has uniform conditions throughout. Every garden is a composite of microclimates and even within the smallest gardens many mini-zones, as I like to think of them, can be found. Think of them as little gardens within little gardens.

The variations in temperature is often the result of variations in elevation, site exposure and airflow; and these can be manipulated to produce a range of plant diversity.

A berm (or mound) can be situated to face south for more sun. Tall brushy shrubs can block harsh sunlit areas. Dark stones absorb heat, thus reducing frost risk. White painted walls will reflect heat and so reduce heat gain.

But a vibrant garden takes advantage of what’s already there. For example, cold air is heavy and dense, it flows down slopes and settles in low-lying areas, getting caught against hedges and fences. Frost is more likely to occur in these areas, which are known as frost pockets. So here, you’d want to plant the hardiest plants, which often means choosing plants for a zone colder than your overall zone site.

Another variable is wind. Wind has a tendency to swish around the corners of buildings or hurl through openings between trees. Best not to plant in these corridors. Years ago some friends planted two locust trees; one on the south side in front of the house, the other on the eastern side slightly behind the house. The more protected one is strong and big. The other one looks a little mangled as the wind periodically takes off some of the branches.

Bare ground can lose 20 percent of its temperature when shadows hit it, and hot spots occur anywhere if no shade is available. Exposed western and southern walls, particularly light colored, will also saturate an area with heat. Plants that like full sun—hollyhocks easily come to mind—love these spots. Dark walls and mulch absorb heat.

Moist shady areas that rarely get any sun at all call for plants that are happiest in cooler climates like groundcovers such as Vinca and Bishop’s Weed. Shrubs that prefer these cooler places are Viburnum and Spiraea.

Each microclimate provides an opportunity to garden in a different way and to use each site to its best advantage. By keeping these mini-zones in mind and working with the natural laws of sun, wind, shade and water, any garden will fare much better through all the seasons.