Jean Pittman, Sanders, Kayla, Strahan, Ronald E., Voitier, Matthew, Beasley, Jeffrey S., Fields, Jeb S. | 7/17/2018 4:17:32 PM
Photo by Jean Pittman
2018 Louisiana Super Plants
Celosia ( Celosia argentea )
Our spring 2018 induction into the Louisiana Super Plants program is the Intenz Classic celosia. These are full-sun, warm-season bedding plants that thrive in the Louisiana landscape. Intenz Classic celosia is a low-maintenance plant can take the heat and will continue to provide attractive foliage throughout the summer and fall. The abundant and long-lasting purple flowers bloom from spring until fall and are an excellent visual signature that will attract bees and butterflies throughout the growing season. An upright growth habit with flower stalks, the Intenz Classic will grow 16 to 18 inches tall and 12 to 14 inches wide and will fare wonderfully in landscape beds or containers. Space Intenz Classic celosia about 8 to 12 inches apart in landscape beds to allow full spreading. These are great drought- and heat-tolerant plants.
Hydrangea ( Hydrangea paniculata )
The 2018 Louisiana Super Plants introductions include Limelight hydrangeas. Hydrangeas are very showy plants that are used to create great visual impacts in the landscape. Hydrangeas are known for their extraordinary blooms, and Limelight produces a bright lime-green to white inflorescence that is sure to impress. Limelight hydrangeas will grow 6 to 8 feet tall and equally as wide in partial shade and do very well throughout Louisiana. Blooms will express on new growth in early summer and continue until early fall. Limelight does great in the landscape and in containers because of its excessive flowering on upright stems. The Limelight hydrangea prefers well-drained raised beds and tends to require more water than other hydrangea cultivars, making it perfect for Louisiana landscapes. There are no major pest problems associated with the Limelight hydrangea, making it an excellent choice for you home. Remember, these plants will put on a show because they love the limelight!
Photos by Dr. Allen Owings
Southern Magnolia ( Magnolia grandiflora )
Few trees invoke the feeling of the old Southern homestead like our native Southern magnolia, and Little Gem is no exception. Southern magnolias are wonderful pollinators because of their fragrant and white flowers, which begin in late spring and continue until fall. These trees thrive in Louisiana’s climate and native soils and provide year-round landscape aesthetics. For these reasons and many more, the Southern magnolia Little Gem has been selected as a 2018 Louisiana Super Plant. One of the more compact commercial cultivars, Little Gem will grow between 25 and 30 feet tall and 10 and 12 feet wide. Little Gem can be grown as a dense shrub or can be trained to a single leader tree similar to other Southern magnolias. This makes Little Gem a popular selection for medium to large hedges. Little Gem has smaller leaves than many of the other Southern magnolias but provides the dark green foliage with rusty-brown undersides year-round.
Photo by Dan Gill
Louisiana Home Lawn Series
Dr. Jeff Beasley, Dr. Ronald Strahan, Kayla Sanders, Matt Voitier
Common lespedeza (Kummerowia striata [Thunb.] Schindl.), a member of the legume family, is a warm-season annual weed common throughout Louisiana. Lespedeza prefers areas with dry, underfertilized, compacted soils and is often an indicator of low nitrogen levels in the soil. Its stems become woody as it matures, allowing it to better compete with and choke out turfgrass. Lespedeza also has a low growth habit, which makes it difficult to cut when mowing. It emerges from seeds in early spring and becomes established in lawns by summer.
Common lespedeza can be identified by its small, dark-green, oval-shaped leaves that are trifoliate (occurring in sets of three leaflets) with smooth edges. Leaflets have distinct parallel veins that can be nearly perpendicular to the leaflet midvein. As lespedeza matures, its stems become hardened and woody. It typically grows in low-growing, prostrate mats. Lespedeza produces small pink to purple flowers at leaf axils beginning in late summer. For more information on Common lespedeza identification and characterization visit the USDA Plants Database at https://plants.usda.gov.
The best way to prevent or reduce weed encroachment is to maintain a healthy lawn through regular mowing and proper fertilization and soil pH management. Properly maintaining a lawn through these cultural practices promotes dense and vigorous turfgrass and allows the lawn to better compete with weeds. Below are the recommended mowing heights and nitrogen fertility rates recommended for each turfgrass species. In addition to these lawn care practices, manual removal of weeds may also be necessary.
Chemical Control Practices
In addition to cultural practices, herbicide applications may be required to achieve effective weed control. Apply post-emergence herbicides when common lespedeza is observed in the lawn. Post-emergence herbicides like metsulfuron or a product similar to Celsius, which contains thiencarbazone, dicamba and iodosulfuron, are more effective on young, actively growing weeds. Follow-up applications may be necessary to achieve control. Populations of lespedeza that are allowed to persist into late summer can be very difficult to manage. When using any herbicide, you must follow the manufacturer’s labeled directions.
For more information regarding pesticides for turfgrass please reference the Louisiana Suggested Chemical Weed Control Guide at the LSU AgCenter website www.lsuagcenter.com.
Every day, LSU AgCenter extension agents see failing plants, trees or grasses brought to them in search of a fix.
“The plant is just sitting there,” said Lee Rouse, LSU AgCenter horticulture agent in East Baton Rouge Parish. “It’s not growing. It’s not flowering. It’s not fruiting. It’s not performing some task it was meant to do. What is wrong?”
“Typically, the first question is, ‘Have you had a soil test?’” Rouse said.
Soil tests by the LSU AgCenter Soil Testing and Plant Analysis Lab on the LSU campus analyze the soil nutrient content and whether it is acidic or alkaline so experts can recommend any fertilizers and treatments needed to grow certain plants, trees or grasses.
The analysis can pinpoint the exact needs of the soil, Rouse said, so instead of treating plants with a general fertilizer that provides a broad range of nutrients, a gardener can use what is needed.
“You may need those nutrients,” Rouse said. “You may not. You just don’t know until you get a soil test.”
Lee Rouse, LSU AgCenter extension agent for East Baton Rouge Parish, takes a soil sample from a bed using a garden trowel.
Photo by Kyle Peveto
Research associate Lauren Liuzza weights soil samples in the LSU AgCenter Soil Testing and Plant Analysis Lab.
Photo by Kyle Peveto
One of the worst summer weeds we have in Louisiana turfgrass is Virginia buttonweed. The spread of this weed has increased tremendously over the past few years.
Virginia buttonweed (Diodia virginiana ) is a prostrate-growing, mat-forming summer perennial with radially spreading branches. It is easily identified by its opposite leaf arrangements and its four, white star-shaped petals, which sometimes can also have pink streaks through the center of two of the sepals. Virginia buttonweed typically thrives in moist-to-wet soils in the lawn.
This weed gets its name from the seed capsules that resemble buttons that hang on the underside of the stems. Every seed capsule contains two seeds and has close to a 100 percent germination rate. Virginia buttonweed can reproduce by seeds, roots and stem fragments. The combination of these characteristics allows this weed to become the number one weed problem in Southern turfgrass.
This weed will continue to thrive in the lawn even while being mowed at a half inch. If the lawn is being mowed at the appropriate height, 1 to 3 inches depending on variety, then the weed will continue to thrive, set flowers, drop seed and reproduce. Unlike other broadleaf weeds in the lawn, mowing will not inhibit this process.
If you had Virginia buttonweed last year in your lawn, you can expect to see the mother plant re-emerging from the soil and the seeds of the mother plant germinating this month. Chemical control options for Virginia buttonweed include Celsius, Metsulfuron (MSM, Top Shot, or Mansion) Weed Free Zone or Weed-B-Gon. Repeated applications of these herbicides suppressed buttonweed in LSU AgCenter trials. Celsius and Metsulfuron are safe for all Southern turf, except bahiagrass.
Top Shot may be more widely available at your local nurseries and garden centers. Weed-B-Gon and Weed Free Zone are not quite as effective as Celsius and Metsulfuron. But with repeated applications, you will begin to see some suppression of Virginia buttonweed in your turf. Do keep in mind that St. Augustine and centipede grasses can become severely injured by the herbicides Weed Free Zone and Weed-B-Gon if they are applied when temperatures are above 90 degrees. Always be sure to read and follow labeled directions of all pesticides.