Rattlesnake weed tough to get rid of, but right herbicides will do trick

Posted: Sunday, March 27, 2011

In February 2010, I found a weed growing in my yard that I hoped I would never get.

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I have enough weeds to control, including niruri or chamberbitter, greenbrier and pokeweed. Now I have one of the hardest winter weeds to control -- Florida betony.

Florida betony is a member of the mint family. Plants that belong to the mint family have square stems. They are hard to control because most of them spread by underground rhizomes.

Florida betony produces an underground rhizome that will have 2- to 3-inch-long tubers growing off the rhizomes. The tubers look like the rattles on a rattlesnake. This is how it gets its common name -- rattlesnake weed.

These tubers are able to store a large amount of energy, which allows the plant to regrow each year and after herbicide applications. The plant can regenerate from root pieces or portions of the tuber left in the ground.

Florida betony is a winter perennial. It will emerge in late September to early October and will go dormant when the weather gets hot in May. The leaves are opposite one another and are long-stalked and lance-shaped, with toothed margins.

Florida betony will produce flowers that can be white or pink with purple spots. The flowers have two lips. The upper lip is hooded, and the lower one has three lobes.

These flowers produce seed that is viable, so Florida betony can be spread by seed.

The herbicides to be used are determined by where the Florida betony is growing.

In turf grass, products containing atrazine, 2,4-D, dicamba or mecoprop provide good, selective control. Other herbicides have shown some control of Florida betony on turf grass.

Research at the University of Georgia found that the following herbicides provided greater than 70 percent control two months after application: Monument (trifloxysulfuron), Manor (metsulfuron), Revolver, (foramsulfuron) and Speedzone (carfentrazone, 2,4-D ester, mecoprop, and dicamba).

These herbicides are labeled only for turf grass.

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

Dichlobenil cannot be applied over every ornamental plant. Check the label to see where and on what plants Casoron can be used.

This product is not usually found in stores in our area. Some stores can order the product, but it usually comes in a 50-pound bag.

Products containing the active ingredient glyphosate (Roundup) can be used to control this plant in ornamental beds if applied as a spray directly to betony without contacting desirable plants. The glyphosate will move through the plant to the tuber. If the tuber is small enough, the herbicide will kill the plant. However, most of the time it will take two to three applications to kill this weed.

When trying to establish a new bed in soil that contains Florida betony, consider using a 5 percent spray solution of glyphosate one week before cultivating the area. This will help reduce much of the betony population. The applications will need to be repeated to eliminate survivors.

Maintaining a good 4- to 6-inch layer of pine bark or pine straw can eventually smother the betony.

Another control option in plant beds is hand-pulling the betony. In areas that have a layer of mulch, the tubers of the betony can be found growing in the mulch. If the mulch is removed, there is the possibility of removing a large amount of tubers. But if a small piece of the tuber or plant is left, the weed will grow back.

The other day, I thought about the Florida betony that I had found and went to see if it was still there. It wasn't. In late April, I sprayed the weed with 41 percent glyphosate. If herbicides are applied a few weeks before the weed goes dormant, perennial weeds can be controlled more easily.

Florida betony is very tough, but if the right herbicides are used at the right times, this weed can be controlled.

Charles Phillips is a retired Columbia County Extension Service agent and operates Hort Consulting. He can be reached at cphillipshort@com cast.net or at (706) 836-2152.

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