by Lawrence Rozas
Welcome to the Summer Doldrums of gardening. Knowledgeable gardeners forgo adding trees to their landscape this time of the year because newly planted trees struggle under the stressful conditions of a Louisiana summer. Rather, it’s a good time to do routine weeding in the relatively cool, early morning and relax in the shade with a cold drink when the temperature rises later in the day. Better yet, escape the summer heat entirely by moving indoors about 10 am to catch up on the gardening literature you have been putting off or work on your Fall to-do list.
If your plans for the Fall include adding native trees or replacing non-native trees with natives on your residential or commercial property, tree wind resistance should be a consideration. Tropical storms in the summer and fall are not uncommon here in South Louisiana. Avoiding tree species easily damaged or toppled by high winds and selecting those with moderate to high wind resistance is prudent for those of us living so near the Gulf of Mexico.
Recently, James Procter sent me an article published by the University of Florida on the topic. The document reports the results of a study comparing the relative wind resistance for various tree species common in urban areas of the Southeastern Coastal Plain (Duryea and Kampf, 2017). Although the research was conducted in Florida, most of the more than 80 tree species included in the study are native to Louisiana. Non-native species commonly used in residential and commercial landscapes in our area were also included in their study. Damage to trees in urban areas was assessed three to six days following the landfalls of four hurricanes (Erin, Opal, Ivan, and Dennis) that struck the Florida panhandle. The impacts of other hurricanes on trees also were documented using surveys of homeowners. A survey of urban forest professionals in Florida was conducted as well; these professionals were asked to rank the wind resistance of urban trees they observed following hurricanes.
The trees native to Louisiana that showed the highest survival following hurricanes in the study included Live Oak (Quercus virginiana), American Holly (Ilex opaca), Southern Magnolia (Magnolia grandiflora), Wax Myrtle (Morella cerifera), and Sweetgum (Liquidambar styraciflua). Bald Cypress (Taxodium distichum) was also ranked high for wind resistance. Forest professionals ranked Live Oak, Bald Cypress, Native Fringe Tree (Chionanthus virginicus), Native Persimmon (Diospyros virginiana), Hollies (Ilex spp.), and Sparkleberry (Vaccinium arboretum) in the highest wind resistance category. Sweetgum was rated as showing high to medium wind resistance by professionals.
Trees ranked in the lowest wind resistance category included several native species: Pecan (Carya illinoensis), Water Oak (Quercus nigra), Southern Red Oak (Quercus falcata), Cherry Laurel (Prunus caroliniana), and Tulip Tree (Liriodendron tulipifera). Non-native trees in this lowest category included Chinese Elm or Drake Elm (Ulmus parvifolia), Chinese Tallow (Triadica sebifera), and Bradford Pear or Callery Pear (Pyrus calleryana); these three non-natives not only pose a threat to people and property in high winds, they are also considered invasive species and should be avoided for that reason alone. If any of these non-native invasive tree species are on your property, replacing them with a native tree should be a priority.
M. L. Duryea and E. Kampf. 2017. Selecting coastal plain species for wind resistance. FOR119, School of Forest Resources and Conservation Department. University of Florida Institute of Food and Agricultural Science Extension. 15 p. http://edis.ifas.ufl.edu
From the ANPP Jul 2021 Newsletter