February 10, 2018
Dot Zanotti Ingels
Every day our local news meteorologists report on the weather of the Bay Area and then pinpoint the microclimates of a tighter geographical area. For us, that generally means Marin County is taken as one unit. They may break it down to coastal and inland areas, but that is not nearly specific enough when you are planning your home garden plantings.
A microclimate is the climate of a small or restricted area as it differs from the climate of the area surrounding it. The term can refer to an area as small as a few square feet (such as a garden bed) or as large as many square miles.
Have you ever wondered why your neighbor may be having tomatoes ready to pick while yours are still green or that you can grow citrus and they cannot? Across a single location there can be a significant number of varied microclimates. These different microclimates may have atmospheric conditions that differ from the area they are right next to. Some of these variations are because of general atmospheric conditions that are determined by where you live. But by understanding the factors that affect your specific microclimate you can somewhat modify these factors through your garden design. You can change or improve the microclimate on your property to accommodate a larger variety of plants.
What are the factors that affect your personal microclimate? What can you do to make some changes?
• Topography or sloping ground. The angle of the sun or the slope of a property are major factors in determining the solar radiation, the wind exposure and the water flow it receives. You can warm up a north-facing property by creating sun traps like masonry walls, rocks and patios that gather heat in the sun and then slowly release it later. That can help tomatoes ripen sooner and keep your less hardy plants protected from frost.
Providing shade trees or structures can protect south-facing plantings from beating rays. Terracing can dramatically alter the structure of your hilly garden. Even in a small yard, some areas may be more or less exposed to wind than others. The flow of wind can be dramatically altered by mediating its flow by planting hedges or living screens or providing open space in solid fences and walls where wind can mildly pass through instead of tumbling over them.
Water is more than the moisture that we put into the soil. Where it pools in a garden, how much of it you cover or how it flows through your type of soil can be modified and amended.
• Soil and vegetation. The composition of your soil affects your garden microclimate through how much water it retains or how much evaporates from it. A heavy clay soil retains much more moisture than a soil that is predominantly sand. How much moisture a soil retains affects the humidity and temperature of the air above it. The amount of vegetation on a site, along with the soil and water, combine to affect the microclimate, by covering the soil and preventing the loss of heat and moisture from it.
• Artificial structures. How your house is sited means that your eaves and shade patterns are fixed, but remember that the exposure of each can change with the time of day and the season. Other artificial structures are fun to design and provide microclimate adjustment and added personality to your home and garden.
Microclimates are dynamic things that change as you and nature make changes to your property. Mature plantings and the siting of artificial structures evolve and you need to evolve with them. This means making notes about the sun angles in your garden seasonally. Evaluate water patterns and amounts. Consider soil amendment. Keep track of daily temperature variations and wind patterns. Have fun knowing that your microclimate is yours alone!