Botany
Weed of the Month
February, 2010: Stachys floridana, Florida Betony, Rattlesnake Weed
One of our few native plants that is seriously weedy and has become a pest in Florida and beyond.
Stachys floridana (Florida Betony, Rattlesnake Weed)
Photo courtesy of Linda Lee, University of South Carolina Herbarium
Distinguishing Characteristics: Erect perennial herb growing 10 – 15 inches tall, often forming dense colonies; stems slender, usually unbranched, square in cross-section; leaves opposite, the lower ones often with the petiole as long as or longer than the blade, the upper ones nearly sessile; leaf blade oblong to oblong-lanceolate, truncate or subcordate at the base, toothed along the margin, about 1 – 1.5 inches long; flowers borne in whorls on the upper parts of the stem, pale pink with darker lines on the lower lip, about a half-inch long; rhizomes fleshy, white, segmented, resembling the rattle of a rattlesnake.
Distribution: This plant is native to Florida, but during the 1940’s and 1950’s it began to spread through the Southeast. Today it is present throughout the region, from Virginia to Texas, and it has been detected a few places in California.
Occurrence in Florida: It has been collected throughout the state, from Escambia County to Miami-Dade County, but its distribution is spotty in the southern half of the peninsula. It forms dense stands in lawns, ornamental beds, woodlands and disturbed sites, in sun or shade.
Similar Species in Florida: Four additional species of Stachys are native to Florida, but they are all rare and of limited distribution. The Florida Betony might be confused with the Henbit, Lamium amplexicaule, a winter annual, also in the mint family, that is common in northern Florida. The flowering season of the two plants overlaps in the late winter and early spring, but the Henbit has purple flowers. In addition, its leaves are round in general outline, and they have a “wrinkly” texture.
Means of Dispersal: Seeds are borne profusely, but the plant also spreads rapidly by means of its underground rhizomes. Even small parts of the detached rhizome will grow into new plants.
Comments: Although most seriously weedy plants are introduced exotics, a few native species are vigorous enough to be included in this category. The Beggarticks (Bidens alba), Muscadine Grape (Vitis rotundifolia), and Virginia Creeper (Parthenocissus quinquefolia) are three examples in addition to the subject of the present column. Since these plants are native, they are not included on the FLEPPC’s list of invasive species, but the Florida Betony is considered invasive by the State of North Carolina. The curious rhizome that makes this plant such a problem is buried several inches underground and is difficult to remove. It is edible, with a pleasingly crunchy texture and a bland, slightly sweet taste. The plant grows actively in the winter and early spring, and then it is vulnerable to control by herbicides.
Further Information: http://pubs.caes.uga.edu/caespubs/pubs/PDF/C867-11.pdf 
Dr. Richard Weaver, Botanist
Florida Department of Agriculture and Consumer Services
Division of Plant Industry
1911 SW 34 Street
Gainesville, FL 32614
