If you live in a hot climate, there are many plants that may not be able to survive there – at least, not under ordinary circumstances. If you can create a microclimate in your garden, you might be able to coax these plants to grow and survive, despite the hot weather in the surrounding areas.
So, how do you create a cooler microclimate? Some of the best ways to create a cooler microclimate include the clever use of:
- elevation and slope
- rocks, hedges, and walls
- trees and shrubs
- soil amendments
If you take advantage of all of these factors in your garden, then you can create a cooler microclimate for the plants that just cannot take the heat. Let’s get into microclimates, what causes them, and how you can create one yourself.
How to Create a Cooler Microclimate
Before we can create a cooler microclimate, we need to understand what a microclimate is, and how it is created naturally. Then, we can take the steps to create our own cooler microclimate.
What is a Microclimate?
According to Wikipedia, “a microclimate is a local set of atmospheric conditions that differ from those in the surrounding areas.” These microclimate areas can be as small as a few square feet or as large as many square miles.
As far as gardeners are concerned, a microclimate has a different temperature, soil moisture, and sun/shade profile than the surrounding areas.
What Causes a Microclimate?
In nature, a microclimate is caused by things like:
- Elevation (How high is the microclimate above or below the surrounding climate?)
- Slope (How steep is the land within a microclimate? This can affect how water flows and drains.)
- Closeness to Mountains (For example, a valley between two mountains will form a pocket of cold air, called a cold sink).
- Distance from Water (For example, the “lake effect” occurs when warm air from a lake meets cold air passing by, and creates snow). For more information, check out this article on the lake effect from Wikipedia.
- Exposure to Wind (Natural rock walls, trees, and other factors can block wind entirely, or create a wind tunnel to make it more extreme).
Check out this article from Washington State University for more information on the factors that cause natural microclimates.
How to Change Microclimate (Methods for Creating a Cooler Microclimate)
To create our own cooler microclimate, we can take advantage of the ideas mentioned above. One great way to change your microclimate is by playing with elevation and slope.
Use Elevation and Slope to Create a Cooler Microclimate
If you have a slope in your yard, you can plant near the bottom of it to take advantage of gravity. Any rainfall or irrigation will run downhill and settle near the bottom of the slope.
This will keep the soil near the bottom of the slope nice and moist. Soil that is consistently moist will take longer to warm up in the spring, which will give you cooler soil for a longer time period.
On the other hand, planting at the top of a slope may result in drought conditions for plants, since water will run downhill. Also, the soil on top of a slope will warm up faster, since it is exposed to more sunlight.
Of course, if there are no natural slopes in your yard, you can create a gentle slope by taking dirt from one side of your garden and piling it up in another. Before you start this project, make sure that you orient your garden so that it is facing the right direction (more on this later).
There is another way to use elevation to your advantage. Remember the idea of a cold sink that I mentioned earlier (cold air trapped in a valley between two mountains)?
Well, you can copy this natural phenomenon in your garden (on a smaller scale) to create a cooler microclimate. We know that warm air rises, and on the flip side, cool air sinks.
If you can create an area in your garden that is lower than the surrounding land, then you can trap some cold air in the low-elevation area (like the cold air trapped in the valley between two mountains). You will need to do some digging, but the effort will be worthwhile.
You can create alternating mountains and valleys by digging trenches and using the soil to pile up mounds on either side of the trenches. Then, plant your crops in the trenches (valleys) to give them cooler air and some protection from the sun (at least during the early and late parts of the day).
Just remember that water will drain from the mounds down into the trench. If your soil is heavy clay that does not drain well, consider adding some compost to make it drain better.
For more information, check out my article on how to make soil drain better.
Use a Compass to Create a Cooler Microclimate
I know it sounds crazy to use a compass to create a cooler microclimate, but hear me out. The direction that your garden faces makes a big difference in terms of the sun exposure and wind that your plants will experience.
In the Northern Hemisphere, a north-facing garden will end up with soil that is cool & moist. An east-facing garden will stay cool and get protection from wind.
Check out this article from the Colorado State University for more information on how garden facing affects microclimate.
Before you dig any trenches, build any walls, or plant anything, decide on which direction your garden will face. It will save you a lot of work in the long run!
If you put your garden close to a tree line, hedge, or structure (house, barn, garage, shed) to give it shade, then make sure that the garden is on the north or east side to take advantage of the sun’s path.
Use Rocks, Walls, and Plant Barriers to Create a Cooler Microclimate
Barriers made of stone, wood, and even plants can help to create a cooler microclimate in your garden. These barriers can provide shade to keep soil and plants cooler on sunny days.
You can also use these barriers in a clever way to funnel wind into a tunnel, to help cool down a microclimate in your yard.
You can use all sorts of barriers to provide shade and produce a wind tunnel, including:
- Berms – a berm is just dirt piled up to form a mound, which can be long enough to surround your entire garden.
- Stone Walls – you can build a wall out of stone, which can be expensive and time-consuming. However, a solid stone wall will block the wind, allowing you to direct it to where you want it to go.
- Fences – you can also build a stockade-type fence out of wood or vinyl by purchasing panels from Home Depot or another garden and landscape store.
- Straw – this is a much more economical option than stone walls or wooden fences. All you need to do is build a barrier using bales of straw. Unfortunately, this straw barrier will not last very long, so you will probably need to do it every year. The good news is that you can use the decomposing straw in a compost pile to feed your garden every year. For more information, check out my article on how to make your own compost.
Check out this article from the University of Vermont Extension for information on microclimates in your garden.
Another benefit of barriers is that they can reduce traffic noise from the street in your garden. For more information, check out my article on reducing traffic noise in your garden and my article on plants that make a good sound barrier.
Use Strategic Planting to Create a Cooler Microclimate
It takes some planning, but you can be clever about the plants you put in your garden and where you put them. With a little thought, you can create a cooler microclimate for the plants that need it, without affecting the ones that don’t.
Companion planting is the idea of planting two or more species together so that they can help each other to grow. For example, planting marigolds together with tomatoes can help to protect tomatoes from root-knot nematodes.
In the same way, you can use companion planting to provide shade (and thus cooler soil and air temperatures) for plants that can’t stand the heat.
For example, you can plant taller plants (such as corn, squash, pole beans, or sweet potatoes) to provide shade. Nearby, you can plant shorter crops that prefer shade or cool soil, such as lettuce, spinach, or carrots.
You will need to give the taller plants something to climb on, such as a trellis (lean-to or A-frame). A trellis will serve a dual purpose, since you can put shorter plants that prefer shade under the trellis.
For more information, check out my article on trellises.
Build Structures to Create a Cooler Microclimate
In addition to building trellises, you can also build arbors or pergolas to help create shade, and thus a cooler microclimate for your garden. If you’re not sure about the difference between these structures, here is a summary:
- A trellis is a lattice, which can be freestanding, and always supports plants.
- A pergola can be freestanding, and has sturdy posts to hold up a flat roof, which provides partial or full shade for a deck or patio.
- An arbor is often freestanding, and creates a tunnel to shade a garden gate, path, or bench.
For more information, check out my article on the differences between trellises, pergolas, and arbors.
The best part about these structures is that you can use them as a support for plants to grow up and along. As the plants grow leaves, they can provide shade to other plants underneath the canopy of the structure.
Even without plants climbing up a pergola, you can use a light-colored tarp or fabric cover to provide shade and reflect away sunlight to keep things cool.
Use Soil Amendments to Create a Cooler Microclimate
If you think soil does not matter for your microclimate, think again! The type of soil you have will affect the moisture levels in the ground. This, in turn, will affect the microclimate.
Soil that stays consistently moist will warm up more slowly and stay cooler than dry soil. If your soil is sandy and drains quickly, then even heavy irrigation may not help.
Adding compost to sandy or dry soil will improve water retention. Lighter colored soil will absorb less sunlight and will stay cooler as a result.
For more information, check out my article on how to treat dry soil.
Use Irrigation to Create a Cooler Microclimate
This goes along with the last point – it’s no use having soil that retains moisture if there is not enough to go around! Water your plants frequently or install an irrigation system to give them the water they need.
You might be able to catch rainwater in gutters and barrels and direct it to your plants to save on water bills.
What to Avoid when Creating a Cooler Microclimate
Avoid planting near driveways or patios with dark-colored stones. Dark material will absorb more heat from sunlight during the day, and then release it at night.
Also, avoid planting in a greenhouse or cold frame – it may keep plants alive during the winter, but plants that prefer cool weather (such as lettuce) may bolt early and become bitter if left in these structures for too long.
For more information, check out my article on why lettuce gets bitter.
By now, you know how to create a cooler microclimate. By taking advantage of some ideas from good old Mother Nature, you can make things a little cooler for plants that can’t take the heat.
I hope you found this article helpful – if so, please share it with someone who can use the information. Until next time, stay cool and enjoy your garden’s pleasant microclimate!