Wicked Weeds: Creeping Charlie
By Bonnie Cummings
Just the name, Creeping Charlie, gives one a clue that it is hard to stop! In our area, the familiar common name of creeping charlie is how we have come to know a perennial, non-native invasive weed, more properly called ground ivy. In other areas, Ground Ivy (Glechoma hederacea) has other names such as run-away-robin, field balm and cats-foot. Native to Europe and south-west Asia, this plant was introduced by the early settlers and is now found in all areas of the United States except the Rocky Mountains. “What were they thinking?” you may ask! Ground ivy was cultivated for centuries in its native habitat and had multiple uses as a medicinal herb, salad green, ground cover, potted plant, food flavoring (the Saxon’s used it to flavor, clarify and preserve beer be-fore hops were introduced) and a substitute for animal rennet in cheese making. In short, it came here because it was useful. In light of modern scientific research many of its uses have been debunked and discouraged since it has known toxicity to cattle and horses and suspected toxicity to humans.
Creeping Charlie can be identified by its round to kidney - or even fan - shaped leaves which have round, toothed edges, on a hairy upper surface. Leaves attach via long petioles, in an opposite configuration, to square stems which root at the nodes. When crushed, the plant gives off a distinct scent, another clue to its membership in the mint family. This habit of rooting at the nodes is what gives ground ivy its “creeping” description and makes it so difficult to control. It thrives in moist, shady areas but can do very well in full sun and encroaches into flower beds from lawns where it thrives due to its ground hugging ability to avoid the mower blades. Flowers are blue-purple, bilaterally symmetrical, tubular and attractive to a number of native bee species. Blooming from April to July, each flower produces only 4 seeds and these can remain in the soil for up to two years, sometimes longer, but are not the main reproductive manner for the plant, which relies instead on its stolons to spread it far and wide.
Controls for this invader range from hand pulling in flower beds if the coverage area is manageable to spraying in spring and again in fall with triclopyr, Dicamba or 2,4D among other chemicals, all of which should be used according to the label. Use of borax products is discouraged since borax is damaging to many other desirable plants and to the environment, especially when it penetrates into ground water. When hand pulling is employed, care should be taken to entirely remove the bundles of roots wherever the stem has touched down, as well as at the central plant from which the stolons have spread. Use of the same control chemical should be avoided in multiple years and rotation among available chemicals is recommended in order to prevent resistance. A healthy lawn, kept at 3 inches in height may be the best defense. In some severe cases, the only solution may be glyphosate to entirely kill the affected area.
Sources: Weeds of the Northeast by Uva, Neal and DiTomaso, Weeds of North America by Dickinson and Royer, Wikipedia and Michigan State University publication Ground Ivy Control for Home Lawns (E0006TURF).
Photo Credit: Virginia Tech Week ID Photo Credit: Michigan State University Extension