EDITOR’S NOTE: University of Florida/IFAS Extension Director for Nassau County and Environmental Horticulture Agent III, Rebecca Jordi, addresses questions about landscaping and gardening in northeast Florida. She is also a University of Florida faculty member.
QUESTION: Can you give me the names of crape myrtles which are not susceptible to powdery mildew? I am ready to get rid of the tree I now have and replace it because it never looks healthy. SG
JORDI: The best way to avoid powdery mildew is to plant one of the cultivars bred and selected for resistance to powdery mildew. Additionally, crape myrtle should be planted in sunny locations allowing free air movement so that wet foliage dries quickly. The following cultivars are showing excellent or good resistance to powdery mildew: Semi-dwarf (15 feet) – Acoma (white), Caddo (pink), Hope (blush-white), Pecos (pink), and Tonto (red). Intermediate (up to 20 feet) – Apalachee (orange), Centennial Spirit (dark red), Christiana (deep red), Comanche (coral pink), Hopi (pink), Lipan (red-lavender), Near East (pink), Osage (pink), Osage Blush (pink), Sioux (pink), and Yuma (lavender). Full tree (over 20 feet) – Basham’s Party Pink (lavender pink), Biloxi (pink), Choctaw (pink), Fantasy (white), Kiowa (white), Miami (pink), Muskogee (lavender pink), Natchez (white), Townhouse (white), Tuscarora (coral pink), Tuskegee (pink), Twilight (dark purple), and Wichita (lavender).
One other point I want to discuss is the importance of having a confirmed diagnosis before applying any pesticide. The condition on your crape myrtle is caused by a fungus therefore using insecticides would not be beneficial. The improper application of pesticides means we are not following the guidelines set by the Federal government on the pesticide label. In essence, we are breaking the law. Improper pesticide application wastes time and money and can contribute to the pest resistance. I know it is sometimes difficult to drop specimens by the Extension office but it is essential for us to provide the correct chemical for management. For any of your plant problems attend the free plant clinics at the Yulee office (86026 Pages Dairy Rd., Yulee) – the dates are listed on our website at http://nassau.ifas.ufl.edu. The next plant clinic will be August 6, 2012.
QUESTION: My neighbor has a red crape myrtle but she does not remember the name of it. Can you identify the name for me? VD
JORDI: It is difficult to identify plants down to the cultivar or variety especially when the environment can alter the way a particular characteristic of a tree or shrub will manifest. However, I can give you the name of several red crape myrtle varieties and that should get you started. The red flowering produces blooms throughout the summer into early fall. The first true red crape myrtle was breed and introduced in 1997 by Dr. Carl Whitcomb called Dynamite®. Dr. Whitcomb continued his breeding and later introduced Red Rocket®, Tightwad Red® and Siren Red®, each maturing at a different size than Dynamite®. The U.S. National Arboretum also has an important Lagerstroemia breeding program and recently released red-flowered Arapaho and Cheyenne. A few older selections have long been recognized for their good red flower color, but they never achieved the acclaim and notoriety of these later, improved selections. Thanks to the popularity of Dynamite®, red crape myrtles–new and old–are now very popular and widely available.
QUESTION: I found this in my neighbor’s yard. It grows about waist height – can you tell me what it is? My friend says it is a hibiscus but it doesn’t look like the leaf of any hibiscus I know. TO
JORDI:I am using your photo, which helped me tremendously in identifying this plant. I thought it might be a swamp mallow but I believe it is most likely a Red-leafed hibiscus – so your friend is correct. This hibiscus may be one of the common varieties called ‘Panama Red’, ‘Panama Bronze’ or ‘Red Shield’. It is a short lived perennial which blooms from the spring through the fall. It grows well in full sun to partial shade in cold hardiness zones 8-11. It does not tolerate long dry spells so be prepared to apply some occasional irrigation. It only reaches heights up to 4 feet but it spreads up to 6 feet. The color of the flowers range from rose to pink to cream but the real reason for getting this plant is the foliage. The color of the leaves ranges from burgundy to a shiny, bronze. The leaves are deeply lobed and the edges are serrated. Flower blooming may be somewhat sporadic. It will die back when the cold temperatures arrive but it should return for a few years in the spring.
Rebecca L. Jordi
County Extension Director
UF/IFAS Environmental Horticulture
Nassau County Extension
543350 U.S. Highway #1
Callahan, FL 32011
904 491-7340 or 904 879-1019