According to the Garden Helper’s Dictionary, a micro-climate can be thought of as ‘variations of the climate within a given area, usually influenced by hills, hollows, structures or proximity to bodies of water.’
So what does this mean, and how can it affect gardening and landscape projects around your home?
It could mean that it’s a lot colder (or warmer) where you live, compared with the next town, or the next street . . . or even just 10 feet away from your chosen planting spot.
Gardeners should greet this as wonderful news. Once you begin to understand some of the intricacies of micro-climates, it will allow you to get away with ‘daring’ experiments with plants that normally would not survive in our climate.
For example, there are several citrus trees around town that survived into the teens during the chilly Jan. 7 weekend with little damage. Some were planted facing south, up against a tall building which protected them from the north wind, allowing them to benefit from the heat retained in the building’s exterior walls.
To help readers understand this fascinating subject, here are six micro-climate concepts.
1. Urban Heat Islands
Buildings, roads and other concrete structures within cities absorb heat all day; they then release this warmth slowly at night, and raise the average night temperatures compared to the surrounding outer edges of the city. Notice how Camp Mabry’s low temps are always several degrees warmer than readings from the airport. Since I live in the Round Rock city ‘proper,’ I can get away with more tropical plants at my house than my parents, who live south in Buda.
2. The Effect of Large Bodies of Water
If you live near a lake or pond or the ocean, you’ll notice a high moisture level and humidity in the air. On the plus side, this moderates temperatures of the surrounding area, but it also makes everything seem a little ‘sticky.’ The effects of this extra moisture are most pronounced in coastal areas and large lakes and can create its own weather, i.e. The Great Lakes region ‘lake-effect’ snow storms.
3. Cold air sinks
The higher you live on a hill, the warmer in general you will be relative to the valley beneath you. Even small hills can make a difference. The last killing frost we had about 10 years ago saw agaves frozen solid at the bottom of my street; those of us at the top of the hill had little damage.
4. Compass Points
Different sides of your home (or even a privacy fence) can have very different temperatures in both the summer and winter. Dig in plants that need cooler temps year round on the east or north side of the house. Put plants in need of extra winter protection on the west or south side. This way they’ll get as much heat in the winter as possible and protection from the killing north winds.
Plants planted out in an exposed area will feel fluctuations in temperature more intensely than those set closer to a structure. For example, it’s better to plant something with larger leaves that may suffer sunscald when facing west or south or damage from north winds along an opposite facing wall. It is also easier to offer plants some protection from afternoon summer heat by keeping them closer to a north or east facing wall, fence or even a taller plant.
6. Reflective surfaces
Lighter colors, including concrete, painted surfaces and limestone, reflect more heat than darker ones. In the summer this heat bouncing back on to a plant could cook sensitive leaves on a 100 degree day leaving them brown on the edges with pale, washed out spots in the inner areas. Alternatively, these same places can be a life-saver for heat tolerant plants that need extra winter heat.
Armed with this knowledge, you should hopefully be able to add greater diversity to the collection of plants in your landscape as you explore the peaks and the valleys and protected areas around your home. Happy micro-climate gardening everyone!
If you have a question for Amanda or Chris, send it via email to email@example.com. Or mail a postcard to It’s About Thyme: 11726 Manchaca Road, Austin, TX 78748 www.itsaboutthyme.com