Windblown? Plant To Modify The Draft

Windblown? Plant To Modify The Draft

Everyone has felt the cooling effects of a breeze on a hot, summer day. Wind chill charts show us how an increase in wind speed can increase the discomfort of a frosty winter morning. What about the plants we grow in our landscapes and in our gardens? How are they affected by the winds, gentle and strong, warm and cold?

In the Rogue Valley, there exists a corridor extending from Ashland through Phoenix, situated to the east of I-5, where the wind seems to blow nearly every day of the year. It howls with the approach of winter storms and moderates the high temperatures of summer afternoons. In observing the trees that grow here, the first aspect that one notices is that the native white oaks appear to be shorter here than in other parts of the valley. Some cultivated trees, like flowering plums, have a decided lean to the south, indicating strong wind flows from the north.

Studies performed under controlled conditions have shown that the stronger the constant velocity of the wind, the shorter the overall height of the plant compared to those not exposed to wind. Plants exposed to these controlled winds also developed smaller leaves. This would be advantageous to the plant for two reasons: lowered transpiration rate and less damage from tearing and stripping.

In response to the detrimental effects of wind and its economic impact on agriculture, the use of windbreaks has been advocated for many years. A well-constructed windbreak can be an advantage to the homeowners in windy areas as well. Part science, part art, a windbreak can increase fruit yields, provide comfort and shelter for wildlife and can modify the climate enough to extend the growing season and the range of plants grown.

Windbreaks should never be completely solid or the turbulence they create downwind will negate any benefit derived from their use. Allowing approximately 40 percent of the wind to pass through is about ideal. Plants come near to this density. Planting multiple rows of plants of increasing height can increase the length of the area of coverage.

The trees and shrubs used for a windbreak or planting on exposed sites should be chosen for their mature sizes and the amount of protection necessary. The use of native plants is highly encouraged to lessen the need for supplementary irrigation. Certain varieties of pine, incense cedar, Arizona cypress and taller junipers are favored for their durability and hardiness.

If you don't have room to plant a windbreak, select open, small-leafed trees and shrubs that will allow wind to flow through them. Hornbeams, willows, Norway spruce and hawthorns are fine trees to use. Staghorn sumac, mugho pine, red-twig dogwood and snowball bush are large shrubs that fare well in windy conditions.

When planting in exposed locations, it is natural to want to tie plants, especially trees, tightly to stakes until they are well established to prevent wind-throw. While it may be advisable to initially provide support, do not over-fasten plants to stakes. The idea is to allow movement in the trunk and branches while preventing the plant from toppling. It is the repeated flexing of the core of the plant that causes expansion and strengthening of the trunk and allows the plant to support itself. A tightly bound tree will never develop the caliper of stem required and will become dependent on the stake for its support.

Friend or foe, beneficent or malevolent, the wind is part of our environment. Planting to deal with it is a big part of the world of gardening.

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