May 19, 2023 11 min read 0 Comments
Understanding and working with the microclimates on your property and in your garden offers a number of benefits. Using permaculture design principles to influence these microclimates can increase crop yields, widen the variety of plants you can grow, and extend the growing season. Even in small spaces or temporary container gardens on an apartment balcony can benefit from applying these design principles
A microclimate is any region, big or small, where the climate is noticeably and consistently different from the surrounding area. It helps here to understand what we mean by climate as well. The climate of a given area is the weather patterns over time; this includes the temperature, humidity, wind patterns, and precipitation. So a microclimate occurs when natural features or intentional modifications create an area where these factors are impacted.
The simplest example of a microclimate is to imagine sitting under a shade tree on a hot day while you contemplate your garden. The temperature under the tree is lower. There is less available light so understory plants are shorter. The humidity is likely higher. If you are on the leeward side of the trunk you are sheltered from the wind. The existence of the tree has created a tiny area of climate that is noticeably different from standing exposed to sun and wind even a few feet away.
From a macro perspective, microclimates are often noted when looking at urban and rural settings. In the urban setting, things like the asphalt, concrete and buildings absorb the energy of the sun, heating up and then releasing that heat back into the air. This results in higher urban temperatures than those in rural settings. In the rural settings, factors like proximity to water may cool down the air, resulting in more moderate climates at times, which is advantageous to areas with high summer temperatures. Water bodies like lakes, ponds, reservoirs and streams not only affect temperature levels, but also humidity levels (more water in the air).
The soil itself can cause climatic variances as well, mostly due to the amount of moisture absorbed and then evaporated back into the air. Clay soils retain more moisture than sandy soils and can affect the humidity and air temperatures of an area. Soil color will also have an affect on the temperature and radiated light. All of these can be mitigated with mulching and soil amendments.
The slope of the land is another factor that can affect climates, with some areas receiving more sun radiation than others. As the days get shorter and the sun sits lower in the sky, shadows can lengthen and block out entire portions of beds. Therefore, it’s a good idea to place garden structures further apart during these times to allow for more direct sun exposure. Sometimes, the wind can whip up and around slopes, damaging plants. Areas like this should be treated like any high wind area; setting up wind-blocks, either naturally or synthetically, can help protect plants and infrastructure. Even though strong winds may not directly kill plants, they can stunt growth or otherwise set the plant back.
There are four central factors that impact and can be manipulated to create microclimates:
The most important benefits of creating microclimates all come from the moderation of extremes. This moderation can help plants to survive outside their preferred growing zones and expand your growing options significantly. A variety of planting and growing tasks can be made more efficient and easier with an understanding of your existing microclimates or the creation of one.
When selecting crops to grow farmers and gardeners often limit themselves by the suggested growing zone in the seed description. This could be the number of cold hours required for perennials to set fruit or the days above 75℉ needed for tomatoes and peppers to ripen. A little moderation of climate conditions can create warmer or cooler microclimates to allow you to grow crops as much as 2-3 zones beyond your location.
Cooler areas of the garden with dappled shade can be used to keep lettuce and greens growing into the heat of summer without bolting. South facing spaces with plenty of thermal mass can keep heat loving crops happy even if you are prone to late frosts.
Limiting weather and climate related damage to plants and produce not only increases yields it also increases the quality of that produce. Late afternoon shade can prevent sunscald on peppers and tomatoes. Mitigating the high temperatures of the day and maintaining consistent soil moisture lessens the likelihood of flower and bud drop. More flowers means more fruit set and better overall yields.
There was a great study done on Microclimate Modification Using Eco-friendly Nets for High-quality Tomato Transplant Production by Small-scale Farmers in East Africa. They used an insect netting just like ours with a 0.4mm pore size. The increased humidity and protection showed that, “Starting seeds under a net advanced seedling emergence by 2 days and resulted in higher emergence percentage, thicker stem diameter, more leaves, and faster growth leading to early maturity of seedlings and readiness for transplanting. Netting improved root development by increasing root quantity and length.”
Creating microclimates can improve soil and root health by reducing the need for tillage and increasing the water retention of the soil. This article on Innovative Soil Management and Micro-Climate Modulation for Saving Water in Peach Orchards shows how the application of mulch combined with shade netting maintained high yields of quality peaches while reducing the need for irrigation significantly. The shading of the tree canopy reduced transpiration while the mulch reduced evaporation both increasing the humidity under cover and maintaining soil moisture levels.
The use of thermal mass in a microclimate can help save on costs of both heating and cooling. This is because any source of thermal mass, from stones and ponds to water barrels and raised beds, absorbs heat from the sun during the day and releases it overnight. Rock walls and water features are helpful in moderating temperatures for landscape plantings. In hoop houses or gardens raised beds and pots can be dramatically warmer than in ground plantings. This is particularly true of dark colored pots like black grow bags that hold significant heat overnight protecting tender crops from light frosts that can damage inground plantings.
When applying permaculture principles to your space your most powerful tool is observation. An ideal first step is to map out your property visually. Identify all structures, fences and trees as well as any significant slopes. Include in your map prevailing wind patterns.
Once you have a simple map you can add shade patterns and seasonality of those patterns. A line of cypress trees planted as a windbreak will produce a year round shade that lengthens northward as the sun sinks south in the winter. An oak tree will produce dappled shade in the spring and fall but a solid mass of shade in high summer.
Thermal mass can be shown by shading areas of your map in reds, yellows and blues. The larger and darker in color any large feature is the more moderation it will generate. Light colored features like a solid white fence will reflect light and heat back to nearby plants and create a significantly warmer microclimate on sunny days.
Observation is key for this step. The easiest way to identify possible frost pockets is to go out in the early morning and see where frost or heavy dew has gathered, often in low points in the land or under shade from trees. You will notice that some areas shaded by buildings do not show the same accumulation due to the moderating effect of thermal mass. These areas can be good places for trees that need significant chill hours or to keep your cool weather greens in the summer. Conversely, definitely not the place to put in peppers or tomatoes.
Knowing the composition of your soil (sand, silt and clay) will provide a baseline for the effect it can have. If you are not sure what your soil composition is this article shows How to Determine the Texture of Soil. When searching out favorable microclimates on your property it is ideal to test the soil in each area that you plan to treat separately. This will allow you to fine tune your amending and mulching practices.
There are a plethora of ways to create microclimates; some may last a season while others become permanent features of the landscape. Shade cloth, frost blankets, insect netting and moveable thermal mass (think 55 gallon water drums painted black) are all temporary ways to impact small areas. Even installing a hoop house or caterpillar tunnel can be lumped in with the somewhat temporary changes to a microclimate in your growing space.
Earth mounds, planted windbreaks and ponds are much more permanent installations.
Earth mound garden beds, commonly called hügelkultur, are a popular way to create garden microclimates and microclimate pockets within the garden. This fact sheet from Oklahoma State University does a great job of explaining how to build one. If your growing space doesn’t have any significant slopes, earth mounds are a great way to create some.
Planted windbreaks are a wonderful way to protect both plants and buildings if you have the ability and the space. They do not have to be huge walls of cypress trees though they can be. A windbreak can be as simple as putting an assortment of hardy shrubs on the windward side of your garden. Hedges of garden roses or other brambles like blackberries can make great windbreaks and provide nesting habitat for songbirds.
Shade cloth comes in a variety of colors and densities that allow you to customize a microclimate ideal for growing high value crops. Any color of shade cloth will protect crops from excess solar radiation. White will also help to reflect heat while aluminum coated shade cloth called aluminet can act as a thermal blanket overnight to moderate temperature shifts. To learn more about the types of shade cloth offered in our article Monofilament vs. Tape Shade Cloth.
Straw bales can be used in a myriad of ways to help moderate problems in the garden. Bales can be used to create small wind breaks, generate thermal mass, mulch, and even to create temporary berms to help hold water on the landscape.
South facing slopes in the northern hemisphere warm up quicker in the spring and receive more sunlight during the winter months. There are many ways to plant effectively on slopes from terracing to berm and swale and beyond. If you have a significant slope you would like to cultivate it is worth researching further to decide on the best method for your situation.
Are you looking for a temporary or permanent solution? Do you have the patience to wait for a windbreak or shade tree to grow in? Are you looking to grow annual crops or put perennials on the landscape?
Check the recommended growing zone and decide if you can create enough of a moderation to allow it to grow. Think about water patterns through the year. That boggy frost pocket where it is too wet for fruit trees might be just the place for a lovely bog garden or a willow tree that can provide you with building materials.
These will depend entirely on what you plan to build. It is advisable to have all your supplies arranged ahead of time in order to complete the project as quickly as possible. Particularly in the rainy season a half finished project can lead to issues.
Once your climate is set up you can add in your plants and get growing.
Sometimes the microclimates we try to set up don’t work exactly as planned. Make observations of your new planting area a few different times during the day to ensure it is performing the way you expected.
You can make adjustments over time as you become familiar with how each area behaves. It is important to make these observations again as the seasons change. You may find that a wind break you set up has become a shade structure as fall turns to winter. Or you may find that a straw berm you set up is holding too much water in the rainy season and needs a few channels cut to allow overflow to run out.
Microclimates can be created with temporary installations to mimic more permanent features of a permaculture landscape. Straw bales can be used as berms. Privacy lattice or quick growing vines on a trellis can take the place of a planted windbreak. Shade cloth can be used to cool certain areas and help retain humidity. If you use a little imagination you can find innovative ways to broaden your growing climate even if the land is not yours to modify.
The same principles on mapping and moderating apply even on a small scale at an apartment building or townhome. Light colored south facing walls will give you a warm microclimate with lots of reflected sunlight. Dark colored walls will hold and reflect heat. You can change these with shade cloth or by hanging silage tarp if you are not able to paint walls.
If you cannot put in raised beds you can use large grow bags placed on pallets in the same way.
The best plants to grow in a microclimate are those that take into account the strengths and needs of that particular area.
Heat sinks like dark colored stones can help in small areas. I like to put a few black rocks around tomato seedlings to protect against late frosts. It allows them to be planted out a few weeks earlier than otherwise possible.
Frost blankets can also be used in cooler areas to protect plants overnight.
Permaculture design is a way of using observation and ecological systems thinking to create sustainable and productive landscapes that solve problems and respect the land upon which they are grown. Micro climates are respected, modified or created in permaculture design to help moderate growing conditions and keep resources like water and nutrients within the ecosystem.
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