A microclimate mimics nature and even human behavior. Let’s say it is 105 degrees Fahrenheit on a sunny desert afternoon. What is the first thing you do if you are having to wait outside for your Uber ride? Move 10 feet over and stand or sit in the shade of a tree!
When the weather heats up in summer or cools off in winter, plants feel the changes. Some plants are more sensitive to direct sun, heat or cold than others. Southwest gardeners can use microclimates to cool a plant down or heat up the ground around it in winter. Learn more about growing zones on our growing regions page.
What Is a Microclimate?
Microclimate is a scientific-sounding name for a pocket of an area that can vary in temperature and exposure to the elements. Microclimates can be large, even miles wide. I live in a valley, so my nights can be 5 to 10 degrees colder than some of the nearby mountain slopes. You would think a few hundred feet of elevation would make it colder above. But cold air is heavier than warm air, and flows downhill to gather in a valley. This usually happens in our orchard after the fruit trees have bloomed, killing the fruit with a late spring frost.
Examples of Microclimates
Plants need the same kind of help sometimes. Microclimates can provide that help. Here are a few examples of microclimates:
- Greenhouses. A greenhouse is the perfect microclimate. The glass lets sun in during the day, but the house holds some of that heat in if you seal it up, at least enough to bump up the low temperature and keep cold-sensitive plants alive. Add some heat retainers like black drums filled with water and tile floors, and you heat it up even more. You also hold in more moisture, assuming the greenhouse is airtight.
- Shade. This is a top microclimate for heat-sensitive plants. The best time to shade these plants is in the afternoon, so typically they need to be planted under or near the tree on the east/southeast side. Most native and xeric plants need some sun to flower and thrive. With a little planning, you can plant them so they get plenty of morning/early afternoon sun.
- Walls and Hardscaping. In most cases, walls, fences and boulders can help shelter a plant from winds and cold. The hard materials gather heat from the sun and radiate that heat to a nearby plant at night. Walls also can be used to shade plants from hot afternoon sun if they run north-south and are west of the plant’s location. The plant needs to be close enough to be in the wall’s shadow, but not so close it is affected by poor air circulation and trapped cold (or heat).
- Containers and Raised Beds. Containers can help or hurt a plant in their microclimate role. They help because you can move them around into shade or sun to create microclimates for plants indoors and out or winter over cacti and other heat-loving plants indoors. Containers do not protect plants as well in winter, however, as the ground does. The container cools to the air temperature around it, exposing the roots to colder air than if in the ground. You can move containers against south-facing walls in winter. Raised beds that run east to west warm up faster in the spring, and any new vegetables or ornamentals planted on the south side of the beds should grow better.
- Exposure. South and west-facing walls get much more heat, especially in summer. Place plants that need a little cooler exposure on the north side of your house.
Tips for Gardening With Microclimates
A microclimate can go only so far – you can’t keep a plant alive all summer outside in the desert if it is a lover of cool temperatures and shade. And you can’t warm up your garden 20 degrees on a winter night. Still, microclimates can cut your work and increase your plant’s chance of success; here are a few tips to help:
- Remember how the sun’s path shifts by season and plan accordingly if you want to cool (shade) a plant or heat it.
- Even small changes, like adding gravel or organic mulch around a bed or plant, can be a microclimate.
- Another great way to create a microclimate is with cloths – a good strip of shade cloth can cool a tomato or block intense sun on your succulent, and row cover can help protect plants from cold.
- Mimic nature in your hot garden. If you have a large berm with xeric plants, place the one that least likes heat in the afternoon shade of another plant or the hill, or in a valley below, such as a dry river bed.
- If a plant is not doing well, it might be getting too much shade or sun. Think about moving the plant next season for better success.
Check out my zinnia microclimate experiment over on Gardening in a Drought to see how microclimates affected the annuals.