Sometimes folklore and science actually intersect, though often in unexpected ways. Take for instance, the case of ground ivy (Glechoma hederacea), a common and invasive perennial weed in Iowa lawns and gardens. Ground ivy is known by a variety of names, including Creeping Charlie, Creeping Jenny, and Ground-Over the-Gill.
Ground ivy spreads by seed and the vining stems which root at their nodes. The leaves of ground ivy are round or kidney-shaped with scalloped margins. Stems are four-sided. Flowers are small, bluish-purple and funnel-shaped. Ground ivy thrives in damp, shady areas, but also grows well in sunny locations. A member of the mint family, ground ivy produces a minty odor when cut or crushed.
Originally brought to the United States from Europe as a ground cover, the plant soon became a pest because of its spreading habit. Enter the "hero" of the story: the common household product called Twenty Mule Team Borax. Borax is actually sodium tetraborate, a white, crystalline, mineral salt formed in the beds of ancient lakes millions of years ago. As early as the 1920s, this mineral was being used not only for its cleaning properties, but for its ability to eradicate weeds.
Through trial and error, people found that borax could kill ground ivy. Why did the borax work? Borax contains boron, an important plant micronutrient. However, the difference between plant requirements and toxicity problems is very small. When excessive quantities are present, boron can damage and even destroy plants. We also know that grasses tend to be more tolerant of excess boron than are broadleaves.
But there is little research information on how borax affects turf and ornamentals in the home landscape. So in 1991, Harlene Hatterman-Valenti, ISU horticulture graduate student; and Nick Christians, ISU horticulture professor; conducted research on the effectiveness of borax in control of ground ivy in turfgrass and ornamental situations. Research was conducted over the next two years, and they concluded that, dependent upon weather conditions, borax indeed could indeed match or exceed the performance of common herbicides' in eradicating ground ivy.
They compared various rates of dry and liquid borax with Super Trimec (2,4 D + dicamba + dichlorprop) and Sharpshooter (saturated fatty acids of potassium salts). All borax treatments and Super Trimec provided greater than 90% ground ivy control the spring following application in 1991, when soil moisture was good. In 1992, a dryer year, only liquid borax and Super Trimec controlled 85% of the ground ivy the spring following application. They also found that cooler weather may reduce effectiveness. So if liquid borax and Super Trimec provide comparable results, which would a homeowner want to choose? As you would expect, "it depends."
Homeowners who prefer using conventional herbicides have some effective options. The most effective broadleaf herbicide products are those that contain dicamba. (Two other compounds commonly used in broadleaf herbicides are 2,4-D, and MCPP. Neither material effectively controls ground ivy.) Trimec and Weed-B-Gon Lawn Weed Killer2 are two widely sold products that contain dicamba.
Fall (mid-September through early November) is generally the best time to control ground ivy with conventional broadleaf herbicides. Two applications are usually necessary. The second application should be 10 to 14 days after the first. As always, when using pesticides, read and follow label directions carefully.
Some people, however, are looking for a "natural" weed management product, so the thought of applying a naturally occurring mineral like borax seems to be a better option. It's effective, inexpensive and easily obtained. Hatterman Valenti and Christians found that the damaging effects on bluegrass turf with borax can be longer lasting than Super Trimec (for instance, 10% visual injury 40 weeks after treatment with liquid borax in 1991).
Regardless of the type of material applied (broadleaf herbicide or borax), the key to successful control of ground ivy is proper application. Once the ground ivy has been effectively controlled and an healthy lawn reestablished, the home gardener needs to use good mowing, fertilization, watering, and cultivation practices to maintain a dense, healthy, competitive stand of turfgrass which should help discourage future invasions of this aggressive weed.
The best way to control ground ivy in flower and vegetable gardens is by hand pulling and hoeing. The key to effective control of ground ivy in gardens is persistence. Repeatedly pull and hoe the ground ivy (remove the plant debris to prevent it from rooting) until it has been eliminated. Once destroyed, maintain clean, weed-free borders around flower and vegetable gardens to prevent the ground ivy from "creeping" back in from adjacent areas.
So when callers to the ISU Hortline ask about the borax ground ivy control "recipe," they may sometimes detect a hint of reservation. ISU research does indeed show that the home remedy for ground ivy works. However, several questions remain to be answered: How long does it remain in the soil? What effects, if any, will the boron have on nearby plants? How much borax is too much? These unanswered questions indicate a need for more study in this area. Home owners will usually receive a caution to ensure that they apply it at the recommended rate.
The scientific process can sometimes be a long and winding road, much like the long and winding path of a stem of ground ivy. But research is beginning to untangle the thicket of unknowns about borax's effect on lawns. In the meantime, homeowners do have options in their fight to control ground ivy.
Recipe for Borax control of ground ivy on bluegrass
(Caution: apply over recommended area to avoid toxicity symptoms)
To treat 1,000 sq. feet:
- 10 oz. Twenty Mule Team Borax
- dissolve in 4 oz. warm water
- then dilute in 2.5 gal. water
(Past Horticulture and Home Pest News articles published about managing ground ivy in the lawn and garden can be found in the April 13, 1994 and July 18, 1990 issues. Homeowners may also wish to consult ISU Extension publication Pm-930, "Home lawn care: weed control" for more information about managing weeds in the home landscape."
This article originally appeared in the August 22, 1997 issue, pp. 132-133.