EDITOR’S NOTE: Environmental Horticulture Agent III, Rebecca Jordi, addresses questions about landscaping and gardening in northeast Florida. She is the Extension Director in Nassau County, Florida and also a University of Florida faculty member.
Garden Talk Q & A
QUESTION: You often talk about not overusing Nitrogen fertilizers but isn’t it needed to keep the grass growing? JL
JORDI: I am going to take a recent study and use parts of it to answer your question. Nitrogen is important for growth but we generally are using too much. A little fertilizer can perk up a St. Augustinegrass lawn as spring arrives, but homeowners who overdo it may find they’re growing more than grass.
A University of Florida study suggests repeatedly using large amounts of nitrogen fertilizer can ignite a population explosion of Southern chinch bugs – the No. 1 insect pest of St. Augustinegrass, the state’s most popular turfgrass.
“Everything in moderation,” said Eileen Buss, an associate professor of entomology with UF’s Institute of Food and Agricultural Sciences. “When we try to overly manage a natural system we get the balance out of whack.” UF turfgrass experts advise homeowners to use no more than 1 pound of slow-release nitrogen fertilizer per 1,000 square feet of lawn, a recommendation found in the document “St. Augustinegrass for Florida Lawns,” available at http://edis.ifas.ufl.edu/LH010.
In the study, Southern chinch bugs produced the most eggs on St. Augustinegrass fed the equivalent of 2 pounds nitrogen per 1,000 square feet per month. That rate is a worst-case scenario, Buss said, but not unrealistic because people sometimes deliberately overfertilize in their zest to have the greenest lawn in the neighborhood. Resistant chinch bugs may be able to survive exposure to bifenthrin, a pyrethroid which is the top choice for Southern chinch bug control in Florida. However, pyrethroids should still perform well against nonresistant populations of Southern chinch bugs. Future research may examine the role of the nutrients phosphorus and potassium in chinch bug population growth, and the possibility of overfertilization may reduce turfgrass resistance to chinch bugs. Use 15-0-15 starting in April and use is in small increments until September so the plant can absorb it and grow slowly.
QUESTION: I have a Crown-of-Thorns plant in the shade and it is not doing well. What could be wrong? SD
JORDI: Crown-of-Thorns, Euphorbia milii, a native of Madagascar, is a common garden plant in southern states, especially Florida. It grows best in cold hardiness zones 10-11 which means South Florida for us. Typically it will die back during harsh, cold temperatures here in Northeast Florida so protect it from freezing temperatures.
Crown-of-Thorns produce flowers best in full sun and allow the soil medium to dry out between watering. Overwatering this plant can quickly cause root decay. It is a low-growing evergreen shrub with very thorny grooved stems and branches. The small flowers are produced in clusters of 2-8 at the tips of green flower stem about 1 inch long. The colors of the flowers are pink, red, yellow and white. It is salt and drought tolerant.
Genus Euphorbia includes other commonly available plants such as poinsettia. All parts of the Crown-of-Thorns plant are poisonous. Generally this group of plants is not appetizing to most animals but they will eat it if their normal food supply becomes limited. Drying does not destroy the toxicity of the plant, and Euphorbia in hay may be slightly more palatable to livestock. Contact with the white, milky sap may cause severe blistering as well as intense pain to open cuts or eyes. Honey made from the flowers of these plants may be toxic. Generally horses, cattle, sheep, cats, dogs and humans are affected by Euphorbia and may experience severe irritation of the mouth and gastrointestinal tract, sometimes with hemorrhage and diarrhea. Other general signs include blistering, swelling about the eyes and mouth, excessive salivation and emesis, abdominal pain and weakness. The sap may cause dermatitis. Death is rare. Work horses may suffer severe blisters and loss of hair on the ankles.
QUESTION: What can you tell me about the cardboard plant? I have seen it in garden centers but I am not sure I should buy it. TT
JORDI: The cardboard plant or cardboard cycad, Zamia furfuracea, is a very attractive cycad. The rigid, woody, medium-green foliage of cardboard plant emerges from a large underground storage root and forms a loose, spreading, symmetrical rosette. Providing a tropical landscape effect, cardboard plant’s mounding growth habit is ideally suited for use in containers or as a specimen. Several can be planted together for a lush, tropical effect. They also create a dramatic effect when mass-planted in a shrub border, eventually reaching to six or eight feet tall. However, they are best suited for cold hardiness zones 9b – 11. Remember along the coast in Fernandina, the cold hardiness zone is 9a. It could be tricky but if you are willing to protect it during cold season, you could potentially grow it here. It likes shade to full sun. It is drought and salt tolerant. It really has no diseases and can occasionally have red scale but this can be easily controlled if caught early. Review this complete publication from the University of Florida: http://edis.ifas.ufl.edu/fp618
See all the Landscape Matters clinics happening monthly during 2015, view Nassau County Extension calendar here.
Rebecca L. Jordi
Nassau County Extension Director
UF/IFAS Environmental Horticulture
543350 U.S. Highway #1
Callahan, FL 32011
904-530-6350
http://nassau.ifas.ufl.edu
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