Most of us know about the USDA Hardiness Zones and most gardener’s, including myself, live by them most of the time. With Climate change (I don’t want to hear any nonsense about it, it exists, it is real, move on), these zones are shifting, but the successful gardener knows the right spot for the right plant…..most of the time.
The more rebellious and curious gardeners like to stretch the limits of those zones or even cross into other zones and successfully grow crops by creating microclimates. We all live and garden in microclimates within our hardiness zone (city versus country, altitude, native soil type, etc.) but this post is about intentionally creating an area for raising plants with specific needs.
A microclimate is the climate of a small area that is different from the area around it. It may be warmer or colder, wetter or drier, or more or less prone to frosts.
Microclimates may be quite small – a protected courtyard next to a building, for example, that is warmer than an exposed field nearby. Or a microclimate may be extensive – a band extending several miles inland from a large body of water that moderates temperatures.
At Mount Vernon microclimates are created by the placement of brick walls surrounding one or more sides of a garden or orchard. In the upper garden the whole garden is walled in, the paths are made of gravel and it is in direct sunlight most of the day. This creates a climate ideal for planting vegetables side by side with flowers and also provides a seasonal climate appropriate for sustaining tropical plants (in pots).
In the lower garden the garden has a curved wall along the length of the garden. The wall faces south and absorbs the sun’s radiation all day long and then slowly releases that energy as heat to the nearby garden as the evening and night passes. This keeps the average temperature above the surrounding area and also extends the growing season by delaying the onset of frost.
Not everyone has the ability to create a walled garden, but that doesn’t mean you cannot create microclimates in your own garden. Placing large stones in and among your herb bed creates a warmer environment for heat loving herbs such as sage, rosemary and thyme that mimics their native, hot and arid climate of the Mediterranean. My herb bed is right next to my house, faces south and has several large stones (not quite boulders) of granite and quartz excavated from the yard placed decoratively for visual interest and also for temperature moderation.
Changing the soil structure can also create a microclimate. For example, in the beds where I grow root vegetables such as carrots, leeks, parsnips, etc., I add quite a large amount of coarse sand to the soil. This creates better drainage and better soil structure to prevent root forks and misshapen vegetables. This differs from the soil surrounding this bed and the native soil of the garden.
Adding additional light to an area can create a microclimate. Gazing balls, strategically placed mirrors can add sunlight to areas of the garden that do not get enough throughout the day. I added mirrors to my raspberry bed, while the sun passes this bed all day; it faces north so the additional light reflection warms the area making it more suitable for growing lush berries. I also added a large mirror to the east side of my garage to bounce sunlight into the vegetable garden and toward the bee hive. This will give the bees more morning light and heat to rouse them from their slumber. It will also add much needed light to the vegetable beds that require 8 hours of sunlight a day at least.
Adding a pond to the garden can create a microclimate to grow more lush plants such as hostas that are essentially bog plants, having a water feature such as a pond also makes the immediate surrounding area cooler. I have future plans for a pond in my own garden to enhance the tiny ecosystem.
Look around your garden and find the spots where you want to grow plants but perhaps have hesitated because of the position and see what you can do to cheek the environment in your favor; create microclimates!