Friday's Garden

A weed called cogongrass (CO-gun-grass) is among the world's worst weeds. It is rapidly spreading across the Southeast, and a University of Florida researcher says it's already overtaken kudzu as Florida's most obnoxious weed.
Cogongrass first appeared in the area around Grand Bay, Alabama. The seeds escaped from packing material sent from Japan in 1912. It was intentionally introduced into Mississippi as possible forage in 1921.
Cogongrass was introduced into Florida in the 1930s and 1940s as potential forage and for soil stabilization purposes. However, it was soon clear that cogongrass was of little economic (forage) benefit and could become a serious pest. Consequently, it was placed on the noxious weed list, which prohibits new plantings. Unfortunately, cogongrass was spread by illegal plantings and inadvertently transported in forage and in soil during roadway construction. It does not survive in cultivated areas but becomes established along roadways, in forests and parks. It is now found throughout Florida, from the Panhandle region well into south Florida.
A 2003 survey showed 1.5 million acres of cogongrass across the Southeast, compared to 1 million acres of kudzu. Florida has about a half-million acres of cogongrass, which is well-suited to its role as an aggressive weed. It's a perennial that can spread quickly, by both wind-blown seeds and underground creeping rhizomes. The rhizomes can form a very dense mat in the upper six to eight inches of soil and may comprise as much as 80 percent of the total plant mass. It is the rhizome system that makes this plant particularly hard to control. Elimination of aboveground portions of the plant can be easily accomplished, but if the rhizomes are not killed or removed, rapid re-sprouting and regrowth will occur.
Cogongrass varies greatly in appearance. The leaves usually appear light green, with older leaves becoming orange-brown in color. It can range in size from one to four feet tall. Two things will help you identify this malicious weed. First, each leaf has a prominent, white mid-rib or vein that is distinctly off-center, an unusual characteristic. Secondly, when it flowers, the seedhead looks like the kid's toy, the rabbit's foot.
Cogongrass thrives where fire is a regular occurrence. Researchers believe recent wildfires in Florida may make the problem worse, because fires kill smaller trees and plants, leaving lots of room for cogongrass to move in and take over.
Some Florida counties are making a concerted effort to bring everyone from government officials to landowners to researchers together to eradicate cogongrass. Everyone must work together to try to eradicate this invasive weed, including homeowners who may have a patch of cogongrass on their property.
Cogongrass can be controlled, but it takes an integrated regimen of mowing, coupled with repeated, well-timed herbicide treatments. Selective herbicide choices are limited; research is continuing in this area. In non-crop areas such as rights-of-way and fence rows, products such as glyphosate and imazapyr (Arsenal) will give good control. For more information on how to control invasive plant species, contact your local Extension Service.
After achieving good control of the cogongrass, you must introduce desirable vegetation as quickly as possible to prevent cogongrass from re-infesting the area. Be sure to choose species that colonize rapidly and tolerate the residual effects of your chosen herbicide.
Unfortunately, cogongrass may eventually re-infest in spite of control, so you must continue to remove cogongrass and treat re-infested areas before this grass can regain a foothold.