Being a gardener in Florida is exciting. We have many plants to choose from and the weather is mostly pleasant but always seeming to surprise us. One disadvantage of living in such a place, in addition to having so many growing zones, landscape nurseries, and major shipping ports, is that invasive species that land in Florida don’t like to leave. One newcomer in the lineup of invasive pests is the crape myrtle bark scale (Acanthococcuslagerstroemiae). This invasive insect pest made its way from Texas and, as of a few weeks ago, the only Florida sighting had been in Santa Rosa County. Unfortunately, this pest has now been confirmed in Leon County. Landscapers and gardeners in north Florida should learn how to identify this pest and what options are available for control.
The crape myrtle bark scale, as the name suggests, has a pretty specific host – the crape myrtle (Lagerstroemia spp.). However, in the United States, this scale has also been found feeding on our native beautyberry (Callicarpa americana). Due to the widespread planting of crape myrtles, these should be the gardeners primary focus when looking for this new pest. If present on the tree, it is hard to miss. These scales feed on the bark and are a snow-white color. Being a scale, they produce honeydew that is then covered in black sooty mold. So, if you see a crape myrtle with black branches, look closely and you may see the white scales. If you crush these scales and they leave a pink goo on your fingers, then you very likely have crape myrtle bark scale. Of course, you can send a picture or sample to your local county extension office for confirmation.
Black sooty mold and white scales along the trunk and branches are a tell-tale sign of crape myrtle bark scale. Credit: Mark Tancig, UF/IFAS.
If you do happen to find crape myrtle bark scale in your own landscape, or one that you manage, proper control is important to prevent it from moving along any further. Since scales suck on sap and are protected by an outer shell, systemic insecticides are the preferred product for effective control. These include the neonicotinoids, such as imidacloprid (Merit) and dinotefuran (Safari). The larval stage can be controlled with a horticultural oil, sometimes mixed with another insecticide like bifenthrin (Talstar), however, this will not control the adults. Another option is to completely remove the tree and burn all of the plant material.
Excessive sooty mold has turned these branches black. Be on the lookout for crape myrtles looking like this to help identify crape myrtle bark scale. Credit: Jim Robbins, Univ. of Ark. CES. Retrieved from bugwood.
The crape myrtle bark scale can significantly reduce the aesthetic value of crape myrtles due to the black sooty mold that covers the bark. It is also known to reduce flowering and can lead to thinning of leaves. Since crape myrtles make up a big part of our managed landscapes, let’s all work together to scout for this pest and control it when found. If you have questions, please contact your local county extension office.
Difference in flowering due to crape myrtle bark scale damage. Credit: Jim Robbins, Univ. of Ark. CES. Retrieved from bugwood.
Crape Myrtle season is almost upon us. Soon, every roadside, landscape, and gas station parking lot in the deep south will be lit up in gaudy colors from white to hot pink to fire engine red. A well-placed Crape Myrtle (Lagerstroemia hybrids) can turn even the most boring landscape into a picturesque photo op once summer rolls around. These toughest of flowering trees also ask very little of gardeners to look their best, thriving in many varied settings with a wide range of care given to them. Despite their low-maintenance nature, I see all too many Crape Myrtles languishing in landscapes. While it is difficult to fail with Crape Myrtles, it is not impossible if you site and maintain the trees incorrectly. This summer, follow these three tips to get the most out of the best small tree a southern landscape can offer.
Properly sited, pruned, and maintained crape myrtle. Photo courtesy of Daniel Leonard.
Do not murder your Crape Myrtles. For any reason. No other tree gets lopped off each year to a random height in the belief that it makes it prettier. While your “murdered” crape may indeed produce more flowers the following season, you are permanently damaging the tree, giving rot and decay a foothold, unnecessarily making the tree more susceptible to storm damage, and ultimately shortening the tree’s lifespan. The only pruning that should be done to the species is an occasional “limbing-up” to expose the gorgeous flaky bark underneath and to remove dead or dying branches.
Don’t plant Crape Myrtles in shade. Crape Myrtles perform their best in 6+ hours of blistering full sun per day. Even light shade at various times during the day will greatly reduce flowering, cause the tree to appear thin, and force it to reach for the sun, creating a leggy look. There are many wonderful small landscape trees like Greybeard, Redbud, and Japanese Magnolia that make excellent Crape Myrtle alternatives in shady sites. If you can’t put a Crape in full sun, plant something else.
Keep the area under the canopy free of turfgrass. Turf is a wonderful feature in lawns, just not directly under crape myrtles. Grass does an excellent job of scavenging nutrients and water that otherwise would benefit the crape myrtle above. Also, having grass inside the dripline forces homeowners and landscape professionals to cut the grass right up to the trunk. This often leads to soil compaction from heavy mower traffic and damage from lawnmower decks and string trimmers, which damages the thin Crape Myrtle bark and can even girdle and kill the tree. Either kill out the grass and weeds under the canopy with a nonselective herbicide like Glyphosate and then mulch or plant a shade loving groundcover like Asiatic Jasmine.
Crape Myrtle is one of the most rewarding plants Panhandle gardeners can grow as well as one of the easiest. By following just a few best practices, not overpruning, planting only in full sun and keeping the ground free of turfgrass under the canopy, pretty much every landscape can enjoy success with the species. For more information on growing Crape Myrtle and other gardening topics, reach out to your local UF/IFAS County Extension office! Happy Gardening!
Crape myrtles are all around good tree selections for the landscape. When left in their more natural form with just a little selective pruning, crape myrtles can provide shade during our hot summer days. Learn the many qualities of the crape myrtle with UF IFAS Extension Escambia County.
Burgundy-leaved crapemyrtle is one of the most exciting breeding accomplishments in years. Unlike previous selections, many new crapemyrtle cultivars have leaves that retain dark burgundy coloration from spring budbreak through fall leaf drop. These plants add bold leaf color to a plant already known for its flower power.
Delta Jazz™ was the first crapemyrtle with burgundy-bronze leaves all summer long. Photo by Gary Knox
As is typical of many new plant introductions, the new crapemyrtles are grouped and sold in series, most of which are patented and/or trademarked. Delta Jazz™ was the first crapemyrtle with burgundy-bronze leaves all summer long. This year Delta Jazz™, with pink flowers, is being joined by Delta Eclipse™ (purple flowers). Future years will see Delta Breeze™ (lavender flowers) and Delta Flame™ (red). All have burgundy to bronze leaves from spring through fall and are expected to be mid-size, maturing at heights of 8 to 12 feet.
Another new series with burgundy leaves confusingly is being sold under two names: the Ebony series and the Black Diamond™ series. ‘Ebony & Ivory’ features white flowers that contrast nicely with dark burgundy leaves on red stems. ‘Ebony Embers’ has red flowers on plants with dark burgundy leaves on purple stems. ‘Ebony Fire’ has flowers that are bright red and its leaves are medium burgundy. ‘Ebony Flame’ has dark red flowers and dark burgundy leaves. Finally, ‘Ebony Glow’ is named for its blush white flowers on dark red stems with dark burgundy leaves. These selections are also sold as Black Diamond™ Pure White, Black Diamond™ Red Hot, Black Diamond™ Crimson Red, Black Diamond™ Best Red and Black Diamond™ Blush, respectively. All are expected to grow 8 feet or more in height (regardless of the name!).
‘Ebony Fire’ is a new crapemyrtle with burgundy leaves and bright red flowers. Photo by Gary Knox
The First Editions® Magic™ series of crapemyrtles includes two new selections with burgundy leaves. Moonlight Magic™ has the darkest burgundy leaves I’ve seen so far. Flowers are white and the burgundy leaves are glossy and narrow on a plant expected to grow to a height of 8 to 10 feet. Maturing at 4 to 6 feet, Midnight Magic™ has leaves that are a dull burgundy while flowers are dark pink. Note that other cultivars in the First Editions® Magic™ series (‘Coral Magic’, ‘Plum Magic’, and ‘Purple Magic’) have green leaves.
These cultivars are too new to know how well they will perform in north Florida and the Gulf Coast. The best place to view these cultivars side by side is at the LSU AgCenter, Hammond Research Station, in Hammond, LA. There, Dr. Allen Owings has developed a beautiful garden where he is evaluating crapemyrtles and many other plants. For more information and to read Dr. Owing’s comments on new crapemyrtles, visit http://www.lsuagcenter.com/en/our_offices/research_stations/Hammond/.
All these new cultivars will have the brightest burgundy leaf color when plants are grown in full sun (at least 6 hours of direct sun each day). Any amount of shade will likely result in pale burgundy or burgundy-green leaves, as well as reduced flowering and growth. As with other crapemyrtles, these new cultivars are tolerant of drought, heat, rain, humidity and all but wet soils. When buying crapemyrtle, place the plant in a location where it can grow to its full height without the need to prune it regularly. After planting, sit back and enjoy these crapemyrtles’ bold burgundy foliage as well as the abundance of colorful flowers!
1Extension Specialist and Professor of Environmental Horticulture, University of Florida/IFAS, North Florida Research and Education Center, Quincy, Florida. gwknox@ufl.edu.
Crapemyrtle flowering has been spectacular this year!
While most other garden plants droop from summer’s heat, humidity and heavy rains, crapemyrtle thrives and puts on an outstanding show of flowers all summer and fall. Thanks to modern breeders, there are all sizes of improved hybrid crapemyrtles with flower colors of lavender, purple, white, pink, or red.
Crapemyrtle Cultivar: ‘Tonto’ Image Credit: Gary Knox
Just say “No” to Pruning
Crapemyrtle varieties come in tree-size, patio tree and shrub categories.
Tree-size crapemyrtles grow 25 ft. tall and are ideal as flowering trees. Patio tree-form plants (up to 12 ft.) are beautiful as small, flowering specimen plants near patios, walkways, and entrances. Shrub forms (up to 6 ft.) make excellent accents in a shrub border and smaller types are effective as large groundcovers or container plants.
Crapemyrtle Cultivar: ‘Red Rocket’ Image Credit: Gary Knox
Make sure you buy the right size crapemyrtle for your home. Don’t make the mistake of planting a tree-size crapemyrtle in an area too small for its ultimate size, or you’ll find yourself pruning it hard – and often – to keep it from out-growing its place.
Crapemyrtle Cultivar: ‘Sioux’ Image Credit: Gary Knox
Recommended Varieties
Some of the best tree-size (25 ft.) types are Natchez (white), Red Rocket® (red), Sioux (pink) and Apalachee (lavender). Superior patio tree crapemyrtles (12 ft.) are Acoma (white), Cheyenne (true red), Tonto (fuchsia red), Hopi (pink) and Catawba (purple). Smaller shrub (6 ft.) crapemyrtles are hard to find, but Cherry Dazzle® is a nice mounding red and Pixie White and New Orleans (purple) are good selections.
Planting and Garden Care
When it comes to planting, crapemyrtle is very tolerant and forgiving with three exceptions. First, crapemyrtle needs sun to flower freely, so plant it in a site receiving at least six hours of direct sunlight each day. Secondly, crapemyrtle will not grow in wet soils. Finally, never plant crapemyrtle too deep — if you do so, it will punish you by not flowering for years and years. Planting too deep literally smothers the roots, requiring the crapemyrtle to regenerate a new root system in the soil above.
Crapemyrtle is very drought tolerant and almost seems to thrive on neglect. On the other hand, regular watering and fertilizer will help crapemyrtle grow faster and bigger.
Crapemyrtle Cultivar: ‘Acoma’ Image Credit: Gary Knox
More Beauty on the Way!
Breeders are continuing to improve and introduce new crapemyrtles. Many new varieties were released in the last couple years. In particular, watch for new types with purple-burgundy leaf color all summer long! Time will tell which new ones grow best in Northwest Florida. Stay tuned as the world of crapemyrtle continues to evolve and improve!
*Gary Knox is Professor of Environmental Horticulture with the University of Florida. He is stationed at the North Florida Research and Education Center in Quincy, where he evaluates more than 100 cultivars of crapemyrtle.
