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Micro climate change, part I

Cats and dogs are microclimate masters. They can identify that warm, cozy spot or that spot in the shade better than anyone. This post explores what goes into understanding microclimates. In the next one, we’ll look at how to apply this to your garden—and especially to your Garden Tower.


Microclimates are identifiable climates at a smaller scale. That scale can range from a few miles to a square foot in your garden where a particular plant can be happiest. We deal with microclimates all the time. Think about the coldest part of your house in the winter or the hottest in the summer. The sunny window is another microclimate in your home. Take a tour of your home and think about those spots! How could you use them to your advantage? (Indoor plants, root vegetable or seed storage, summer sleeping areas?)b2ap3_thumbnail_Mogollon-Rim-by-Kevin-Dooley-CC.jpg

 

Just like your home, the garden has many microclimates. Mid-latitude gardeners of the northern hemisphere often identify a shady, northern wall that is challenging. West facing patios where air temperatures warm throughout the day and then have overheat under afternoon sun are uncomfortable, too.

 

As a gardener and designer, the good news is that we can organize and create solutions modifying microclimates for our benefit. Some plants (cooking herbs from the Mediterranean or succulents from the southwest) love those sunny, hot, western areas.

 

There are several factors affecting microclimates: moisture, temperature, winds, vegetation, soil, latitude, elevation and season. Use your observations of your own microclimates to make your home more comfortable and your garden more productive.

 

Where you are in relation to the equator [latitude] affects your general microclimate. Closer to the equator, you may be in the tropical or subtropical zones. The soil in these areas does not hold fertility in the same way mid-latitude, areas. Temperate soils act as a battery for deciduous perennials—storing fertility (organic matter, sugars in roots, etc…) in the soil for use in the next season. The advantage of subtropical and tropical areas is that the sun’s light is more constant—allowing plants to hold their own fertility throughout year. The Polar regions have yet another set of microclimate factors to design for. We unconsciously adapt to the ecological limits of our latitude—internalizing the flow of the seasons, for example. We can’t change these factors—only adapt to them. We can become roficient at placing our productive plants in those mimates that suit them—and making duke they have enough protection through the winter or spring and season to be productive. We can make sure there is enough protection from intense light, rain, and heat to produce in the hotter, more humid zones.

 

Elevation also affects microclimates. At the home scale, plants growing at the top of a hill vs. the bottom can make a difference—they are different microclimates. In the evening, plants at the top of the hill, the mountain, the forest lose the warm air faster than plants on the lower slopes or in the valleys (where heavy cool air can also pool). Apartments in a taller building are more exposed to light and wind, for example. Again, we may not be able to change our elevation (unless we have a large farm, or the ability to change apartments). Usually, we have to get savvy about choosing the right plants to grow—adapted to our elevation—or using greenhouses and shade houses to protect our gardens.

 

Moisture affects microclimates a great deal. The moisture regime you are in—from arid areas to humid areas with dozens of inches of rain each year impact microclimates. Most of our productive plants need more water than less. Moisture in the soil and atmospheric moisture are both important to the life of the plant. For this reason, many plants’ leaves reflect their ability to modify the microclimate immediately around them.

 

A plant’s form reflects a balance between absorbing or deflecting light. The form tells us about how a leaf transpires or absorbs water and materials from the atmosphere. It tells us how the plant holds humidity around itself. A community of plants can, to some extent, regulate their own humidity and light levels. Ever see squash “wilt” in the intense summer heat—even though it just rained? They were lowering their leaves to self-limit light levels. This is how vegetation can affect microclimates.

 

b2ap3_thumbnail_Clouds-on-the-Head-by-photophilde-CC.jpgWinds affect microclimates. It is a good idea to know your prevailing winds in both the summer and winter: they can change. You want to soften or block cold, northern winds or strong winds coming from large bodies of water. Likewise, tall buildings in urban areas speed winds up as they pass between buildings.

 

If you can enhance gentle breezes by creating a “path of trees and shrubs” for them, you can create a pleasant area, too. Letting prevailing, hot summer winds cross a pond or fountain before arriving at your patio, can be a good way to get a cooling, pleasant microclimate benefit.

 

Temperatures fluctuate a great deal in microclimate due to a whole host of other factors—many mentioned already. Latitude affects seasonal temperatures. Higher elevations see cooler temperatures or a wider range of temperatures throughout the day. Areas with more lush vegetation can be shady and cool in the understory and hot and humid at the edges. Temperatures near large bodies of water are more stabile—remaining warmer into the fall. Thermal mass affects microclimates in the garden a great deal. Any dense material that can absorb the sun’s light during the day and radiate heat out to the surrounding area creates thermal mass. Our homes create thermal mass. Brick walkways, and walls, tanks of water, and ponds all create thermal mass. They regulate the temperature and keeping plants warm in the shoulder seasons. Green houses--allow air to warm through the day and trap it inside—cool slower than the surrounding air. Shade houses prevent the sun’s light from entering an area—creating cooler zones in a hot climate.

 

In an upcoming post, we’ll take these factors together help you place your garden elements in just the right places to help them thrive.

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Micro Climate Change, Part II
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