Wind is an oft-neglected but so important design parameter of green roof layout.
Dry, desiccating winds can damage or kill green roof plants faster then drought or a host of other environmental factors.
Included here are two photos of the same black-eye pea plants. One is on a wind protected green roof, the other is on a wind exposed green roof. Note the wind burn on the wind exposed roof plants.
Both looked the same prior to the 48 hour wind storm just leaving.
MetroVerde recorded between 10 and 20 Km/Hr winds on a continual basis for the 48 hours with almost non-existent water vapor or air humidity.
|Florida Green Roof, Wind Protected Green Roof Plants|
|Florida Green Roof, Wind Exposed Green Roof Plants|
Wind can burn or kill green roof plants quickly, taking an otherwise beautiful planting and turning into a brown mess within a matter of days. Even with more than adequate irrigation water applied - simply because the vascular system of the plants cannot keep up with the demand for water in the leaves.
CAM plants and those plants with stomata remaining closed or closing under lack of water conditions must be used as perimeter wind break plants on green roofs with out parapets or other wind protection if the green roof is not otherwise sheltered.
Understand the different types of photosynthesis green roof plants have. For a primer, check out the many articles we have posted before on CAM, C4 and C3 plants.
Other helpful sites are included here;
Great Irish Gardening blog article on wind damage in Ireland to garden plants.
North Carolina State University has another brief yet informative note on wind desiccation of plants.
Very interesting and informative Permaculture Wind Break Site.
Remember, your green roof site may receive plenty or precipitation or irrigation water, but if it is constantly exposed to desiccating winds the plants will experience the effects of wind damage.