April 29, 2016
Ground Ivy Control
I expect to get certain kinds of calls at certain times of the year. My observations as I drove around led me to believe, and my suspicions were confirmed by the large number of calls I've received... 2016 is an excellent year for ground ivy in lawns. There is a small fortune, probably a large fortune, to be made is someone could just find a good use for this weed. One of my Extension co-workers says it best, "Ground ivy is a very horrible weed."
Ground ivy is a perennial broadleaf weed, meaning that it comes back from the roots year after year. This plant is the one that grows low to the ground and sends out runners, has scalloped leaves like a seashell, and has a small purple flower. It also has square stems and smells like mint when you mow over it because it is a member of the mint family.
People want to control it now, but this is very difficult. The major flow of energy and nutrients in the plant in spring is from the roots, where it was stored overwinter, to the above ground portion of the plant. Broadleaf herbicides applied now may burn the top growth and slow it from spreading, but it rarely gives satisfactory control at this time of year.
The optimum time to apply selective herbicides (kills broadleaf plants, but not the grass) is in mid-September to mid-October when there is adequate moisture and warm temperatures, good growing conditions, so the herbicide will be translocated to the roots. The good thing about treating then is, that is also the best time to control other perennial broadleaf weeds like white clover and dandelions.
The other herbicide alternative at any time of year are nonselective products containing glyphosate (Roundup) which will kill everything, weeds and grass, and then you would need to sod or reseed. So it is best to only use this in the spring or fall when you would normally establish new turf. This is a last resort measure when there is not enough grass to try to salvage using a selective broadleaf weed killer.
Even when you apply a selective herbicide in the fall, you will not achieve 100% control with a single application. You will have better luck with two applications about three weeks apart in the fall with the second application spot treating plants you did not control with the first application. Remember, to be effective, the plants need to be actively growing to metabolize the herbicide.
There is another alternative for use on bluegrass lawns ONLY! (Injury may occur on turf type fescues, buffalograss or any other species of turf.) This is based on some research that was conducted at Iowa State University.
Researchers there discovered ground ivy could be controlled with an application of borax. This nutrient can also be toxic to plants above certain levels. Ground ivy cannot tolerate as high a level of borax in the soil as can bluegrass. This difference in tolerance allows us to selectively control ground ivy while leaving bluegrass. Treatment can be made in spring or fall.
A borax-containing detergent (Borateem, 20-Mule Team Borax, etc.) Was dissolved in hot water, allowed to cool, and applied to infested lawns. Three concentrations of borax solution were used in the experiment. In the Iowa State study, each treatment was applied at a rate of 2.5 gallons of water plus the amount of detergent indicated per 1,000 square feet of lawn. Dry detergent was also applied at the highest rate for comparison. Control rates are shown below:
5 ounces 84%
10 ounces 81%
20 ounces 93%
20 ounces (dry) 74%
When treating your lawn, it is important to calibrate your application equipment. The rates are given as so many ounces per 1,000 square feet (an area about 31.5 feet square). You need to measure an area this size and spray it using plain water in your sprayer to determine how much water you apply per 1,000 square feet. Then dissolve the desired amount of detergent in that much water for each 1,000 square feet of lawn you need to treat.
For example, I fill my sprayer with water and spray a 1,000 square foot area. It takes one gallon of water to refill my sprayer so now I know I apply 1 gallon per 1,000 square feet. Then I measure the area I wanted to treat. It is an area 75 feet long and 40 feet wide or 3,000 square feet (75 x 40 = 3,000).
Since I determined I apply one gallon of water per 1,000 square feet and I want to treat 3,000 square feet, I heat three gallons of water and dissolve 60 ounces (3 x 20) of detergent in three gallons of water. I then let the spray solution cool and put it in my sprayer. If I walk at the same speed, this should just cover the 3,000 square feet.
Best results are achieved using a small pump sprayer. This is the easiest way to get a uniform application. People I visited with last year also reported using a sprinkling can or just shaking dry detergent from the box onto the lawn and then watering the lawn to soak it into the soil. Some had good luck with these methods while others indicated skips or areas where they burned the turf because of under- or over-applications.
It is important to note only slight damage to grass occurred when these experiments were conducted on bluegrass lawns. However, the same treatments caused more severe burn to tall fescue lawns. Also, rates higher than 20 ounces per 1,000 square feet were only slightly more effective on ground ivy but caused serious damage to bluegrass.
For more information on ground ivy other lawn weed control, contact your local Nebraska Extension office.