Recognizing Microclimates


How can your neighbor start their peas a week earlier than you always have success while you barely manage to get a cool season crop going at all? Why do their tomatoes last two weeks longer than yours and produce like crazy right up to the end?
The answer could be microclimates. A microclimate is formed by the combination of natural events and features in your yard that accentuate them or protect from them. Several common microclimates are:
1. Exposure to Wind
Exposure to wind can desiccate plants and stunt growth. If your property is open to the prevailing wind, choose hardy, wind resistant shrubs and perennials to go there. Lavender, sage and other shrubby herbs might be a good choice. Or block the wind with a fence or hedge. A hedge or windbreak will block wind for a distance of 10 to 20 times its height. An 8 foot hedge will block wind for 80 to 160 feet.
If your house has a breezeway or other configuration that forms a narrow passage between buildings, this can funnel wind into the area and speed it up. A hedge of wind tolerant plants on the upwind side can make your wind tunnel a more pleasant place to be for both you and your plants.
2. South and West walls
Walls facing south and west concentrate heat by reflecting sunlight back to the surrounding area. Masonry and stucco wall absorb heat and radiate it back at night. In places with cool summers this can help ripen summer vegetables like tomatoes, peppers and eggplants. If you have hot summers shade these walls with sun loving vines like grapes or scarlet runner beans.
3. North walls
Outside the north wall is the coolest place on the property. Planting fruit trees on the north side of the house, where they will be shaded in winter but get some summer sun will keep them from flowering too early if you live in a place that tends to have warm periods followed by more hard freezes.
In warm climates this is also a good location for cool season crops. Leafy greens, peas, beets, members of the cabbage family and radishes can be grown here for a longer season than you might have in other areas of the yard.
4. Cold Air Pockets
Cold air flows downhill and warm air flows uphill. If you are in an area where cold air can flow downhill into your yard, then be blocked by the house, a fence or hedge, that area will be cooler than the surrounding area. Cold air can settle into enclosed patios or yards making them colder than the surrounding area. An outlet for the cold air allows it to flow out, giving slightly more frost protection.
In mild climates fruit trees that need long chill times to set fruit and that tend to flower too early can be grown in these cold air pockets. Apples, apricots, cherries, peaches and pears may do much better if planted in cold air pockets in zones 7 to 10.
Check both winter and summer air flow. The hedge that provides summer wind protection may create winter frost pockets and snowbanks. A snowbank where your summer garden will be is great. A snowbank in your driveway is not.
5. East wall
An east wall gets up to half a day of sunshine, but is much cooler than a west facing wall that gets sun in the afternoon adding to warmer afternoon temperatures. Plants that need plenty of sun but prefer cooler temperatures can be planted on the east side of the house. This is a good place for artichokes, asparagus, onions, potatoes, spinach and others.
6. Overhanging eaves
Eaves can protect the most delicate plants from damage due to heavy rain. It is also a couple of degrees warmer under the eaves, so heat loving vegetables and fruit that might be a bit frost tender for your area can be grown under the eaves. Remember that the eaves keep rain off the plants growing there, so be sure they get enough water.
7. Shade Trees and Overhead Structures
Shade trees and structures create a peasant environment for people and a milder climate for plants growing under them. In summer it is a bit cooler in the shade and in early winter the shade tree or structure can hold the heat radiated from the earth, making it a degree or two warmer and extending the growing season. Lettuce, beans, cucumbers, root vegetables and a variety of herbs will grow in light shade or with only three to five hours of sunlight a day.
8. Sloping ground
As cold air moves downhill along slopes it picks up heat by mixing with the warmer air. Moving air tends to be warmer than stagnant air in low spots or on mountain tops for that reason. South and west facing slopes pick up more heat than flat land, north facing slopes less. Grapes are often planted on south and west facing slopes to take advantage of the extra heat to make the grapes sweeter. In mild climate fruit trees can be planted on north facing slopes for the reasons mentioned above.
9. Dry banks
Water flows over, rather than soaking in on sloping ground. As the water flows it can erode the soil. Perennials with fibrous and deep root systems will hold the soil on these slopes. A south facing slope is an excellent place for an herb garden. Drip irrigation can provide the water that might be needed without causing the bank to erode.
Lynn Doxon started gardening when she was two years old. The had her own garden at the age of 8. She has a PhD in horticulture and worked for several years as an Extension Horticulture Specialist with the New Mexico State University Cooperative Extension Service.
She has an online course in organic gardening that is available at http://www.homegardenblog.net.
Her passion is that everyone, from the renter in the tiniest apartment to the homeowner with an acre of yard will grow some of their own food. She and her husband have the goal of developing an urban farm that provided the majority of their food.

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