July 18, 2015
Dot Zanotti Ingels
While a mild breeze can cool us and keep our skies a bit cleaner, stronger winds can cause anything from mild to severe damage to our gardens. Our large range of microclimates in Marin means that wind impacts us differently depending upon where we live.
The speed of the wind, its duration and the direction from which it comes determine the extent of wind damage. Winds above 30 mph are generally needed to break plants but damage can happen at much lesser wind speeds. In the inland areas of Marin the winds blow up and over the hills and gust through our lower valleys. We can feel like we are in a wind tunnel. At the coast and along the bay shores, wind is almost a constant and is accompanied by fog and salt spray. The tops of our lovely hills are also often windy. Tall or large buildings and even our homes can create their own wind tunnels.
Wind damages in several ways:
• Wind causes water to evaporate from the surface of a leaf about 30 percent faster than on a calm day. If the soil moisture is low (the condition of most soil during drought) so that water absorption by the plant does not match the water it is losing from transpiration off its leaves, water stress is the result. Leaves may appear smaller, look dry especially along the edges, or fall off. A dried-out plant is much less resistant to damage or disease than a well-hydrated plant.
• Strong winds can damage or break branches, leaves and fruit. Young, less established trees could be uprooted. Dense tree canopies can act like sails that catch the wind causing limbs to break or the tree to blow over.
• Along the coast, wind-blown sand can damage and bury root crowns of trees and shrubs.
What can we do to mitigate wind damage in our gardens? Plenty.
• Spend some time noting the wind patterns in your garden. Note the direction it comes from and how it may swirl around. This will help you decide how best to vegetate your space.
• Studies published in the Journal of Arboriculture and Urban Forestry show that thinning a tree does almost nothing to reduce the wind load. If a tree really has to have its wind load reduced, then reducing the overall height and width of a tree is the best option, and height is most important. This makes sense if one looks at trees that grow in wind-blown places. They tend to grow low and wide.
• Manage the water in your garden carefully (again, especially this year). Help your plants to maintain their hydration by keeping the soil evenly moist around them. You may need to give them an extra drink when wind is persistent. Add some extra mulch to cover any bare soil to help the soil retain moisture and the roots to remain more evenly moist. Loose mulches can be blown away with heavy winds and should be wet down before expected gusty winds. If you live with consistent heavier winds, select mulch that is heavier. Install an irrigation system that incorporates a water sensor to help with providing consistent, even watering.
• Choose wind-resistant plants. These tend to bend instead of break with a snap. Plant lists that include trees can be found on the Marin Master Gardener website. If you live by the coast, you need to note whether a species is also able to tolerate the salt spray.
• Use loose, flexible ties to stake young or newly planted trees. Your nursery professional can advise you how to best do this and how long you should provide staking before your tree can make it on its own. Tree canopies should be thinned to allow wind to pass through.
• Provide your yard with windscreens. These can be done with structures, natural elements or plants. Your home provides a screen for a portion of your space. A fence that is at right angles to the wind direction changes the wind pattern. Pergola structures or tent-like awnings with one side closed can work, too. Make sure that they are not completely solid. They need to be porous enough to allow some wind to pass through or they, too, can be wind damaged. If you are planning a large structure, you may be wise to contact a landscape professional.
• Leafy plants and hedges can also buffer a seating area or sensitive plant. Again, the plants need to be selected for wind tolerance in your microclimate.