When planning for planting this season, consider the microclimates in your yard. A microclimate is a local set of atmospheric conditions that differ from those in the surrounding areas, often with a slight difference, but sometimes with a substantial one. The term may refer to areas as small as a few square feet (for example, a garden bed).*

A microclimate can offer an opportunity as a small growing region for plants that may not thrive in the broader area.* Microclimates can be used to our advantage as gardeners, if we try to find the differences in our gardens that determine which plants will grow where, and then carefully choose and position our plants.

For example, microclimates can exist near our houses, where brick, concrete, and asphalt absorb the sun’s energy, heat up, and re-radiate that heat into the air: the resulting heat island is a kind of microclimate. The sheltered heat islands near our houses can reduce the severity of winter for our plants, and because of the slightly warmer temperature, the plants will grow more quickly in the spring. There is a southeast-facing microclimate outside my front door. As the sun moves from east to west it hits this area for most of the day. The sides of the house form a right angle, a corner, and the area contains a paved brick pathway bordered on three sides by gardens that are about three feet wide. The heat from the sun and from the house, combined with the shelter from wind, enable the perennials there to grow two weeks earlier than those in other parts of my yard, so it is similar to a zone six climate there.

Some more details on microclimates:

Another contributing factor of microclimates is the slope or aspect of an area. South-facing slopes in the Northern Hemisphere are exposed to more direct sunlight than opposite slopes, and are therefore warmer for longer periods of time, giving the slope a warmer microclimate than the areas around the slope. The lowest area of a glen may sometimes frost sooner or harder than a nearby spot uphill, because cold air sinks, a drying breeze may not reach the lowest bottom, and humidity lingers and precipitates, then freezes. The area in a developed industrial park may vary greatly from a wooded park nearby, as natural flora in parks absorb light and heat in leaves that a building roof or parking lot just radiates back into the air. Microclimates can exist near bodies of water, which may cool the local atmosphere, The type of soil found in an area can also affect microclimates. For example, soils heavy in clay can act like pavement, moderating the near ground temperature. On the other hand, if soil has many air pockets, then the heat could be trapped underneath the topsoil, resulting in the increased possibility of frost at ground level *