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'Rattlesnake weed' hard to control in yard, garden

By Mark Czarnota
University of Georgia

Because of its name, many people think Florida betony (Stachys floridana) escaped its Florida borders to become a problem weed in turf and ornamentals from North Carolina to Texas.

Actually, we're not 100-percent certain of the plant's origin. Wherever it came from, though, it's hard to control in your yard and garden.

Florida betony is a winter perennial. Like most plants in the Labiatae family, it has a square stem with aromatic, opposite leaves. Sometimes called Florida hedgenettle, its flowers are usually pink and have a classic mint-like structure.

Unlike its relatives, Florida betony produces unique tubers that look like the rattles of a rattlesnake, giving it the "rattlesnake weed" name by which it's sometimes known.

Have a rattle?

These "rattlesnake" tubers can grow to more than 3 feet long in soils with a high sand content. Many people relish them for their crisp, succulent flavor. Who knows? Maybe one day we'll be figuring out how to grow Florida betony instead of killing it.

Florida betony is dormant during the hot, humid summers of the South. In most of Georgia, it starts growing in early to mid fall, slows in the extreme cold of winter and continues until late spring.

We don't have a lot of information on controlling betony. In turfgrass, though, products containing atrazine, 2,4-D, dicamba or mecoprop provide good selective control.

Ornamental choices

In ornamentals, dichlobenil, sold under the trade name Casoron, provides excellent control of Florida betony in select established woody ornamentals.

Products containing the active ingredient glyphosate, such as Roundup, can provide some control if sprayed or applied directly to the betony without contacting desirable plants.

Consider using glyphosate if you're going to put new ornamental plants in an area containing betony. Spray a 5-percent solution of glyphosate, using a product that's 41-percent glyphosate or greater, one week before you cultivate the area. Repeat applications to eliminate survivors will be necessary.

All of these products work well if you use them according to their labels. If you prefer the nonchemical route, maintaining a good 4- to 6-inch layer of pine bark or pine straw should eventually smother the betony.

New products

Many new herbicides have been introduced to the turfgrass market. Preliminary testing has shown that some provide excellent control of Florida betony.

In 2004 and 2005, the University of Georgia ran trials in several places with heavy Florida betony infestations. The sites averaged 41 betony shoots per square foot during both years.

In these tests, these herbicides provided greater than 70-percent control two months after being applied: Monument (trifloxysulfuron), Manor (metsulfuron), Revolver, (foramsulfuron) and Speedzone (carfentrazone, 2,4-D Ester, mecoprop and dicamba).

Unfortunately, all of these products are labeled only for use in turfgrass. For now, frustrated gardeners will still have to rely on hand-pulling, mulch, Casoron and glyphosate to keep this weedy menace at bay.

Anyone for some fresh betony tubers in your salad?

(Mark Czarnota is an assistant professor of horticulture with the University of Georgia College of Agricultural and Environmental Sciences.)

(Mark Czarnota is an extension horticulturist with the University of Georgia College of Agricultural and Environmental Sciences.)

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