MDC says now is the time to defend against invasive bush honeysuckle

St. Louis, Mo.—Everything green is not necessarily good. That especially holds true for bush honeysuckle (Lonicera maackii). Homeowners who have seen it take over their yards know firsthand the challenges that Missouri Department of Conservation (MDC) land managers face to keep the dreaded invasive plant from monopolizing our native habitats. The plant is particularly a problem in the St. Louis region.

The good news is bush honeysuckle's advantage can also be its Achilles heel because now is the best time to fight it.

It seemed like a good idea in the 1970s to introduce a plant from Asia that grows fast, produces sweet-smelling blossoms in spring and bright red berries in fall. But what appeared to be the ticket to quickly green up barren spaces soon became a curse as the plant began to expand unchecked like green wildfire.

One advantage bush honeysuckle has is that it greens up before our native vegetation in the spring, and remains green longer into the fall. This gives it both a head start at the beginning and an extra bonus at the end of the growing season for shading out other plants. Bush honeysuckle has another weapon in its arsenal, too. "It produces an allelopathic chemical in its root system which inhibits the growth of native plants," said MDC Wildlife Biologist Erin Shank.

Shank spends a great deal of time fighting bush honeysuckle on the MDC areas she manages. She said that its late green up can also aid homeowners in their attack against the invasive plant. "It's really easy to identify right now," Shank said. "Our native vegetation is not green anymore this time of year so bush honeysuckle really stands out."

The plant's active state also makes it susceptible to treating its foliage with herbicides. "You can do so with minimal to no damage to native vegetation because natives are dormant and won't uptake the chemical," Shank advised.

Shank said the first weeks of November are ideal for foliar spraying of honeysuckle. Such treatment is most effective on young to middle-aged stands that average less than 7 feet in height. The most efficient tool for foliar treatment is a mist blower, which is most useful on areas larger than 1 acre. Foliar spraying can also be accomplished less expensively with simple backpack sprayers. Shank recommends a 3 percent glyphosate (Roundup) solution with an added surfactant. Coat as much of the foliage as possible. Foliar spray when weather forecast predicts dry conditions for at least four hours after treatment.

When plants are over 7 feet high, cutting and stump treating honeysuckle is necessary. This practice can be done any time of year when the temperature is above freezing though there is some evidence that mid-autumn timing may be more effective. Cut stumps as low to the ground as possible, then treat the stump with 20 percent glyphosate solution using a squirt bottle within 10 minutes. It is crucial to treat the stump quickly after cutting. The low humidity conditions of fall cause stumps to dry enough in a short time to inhibit the uptake of the chemical to the root system. The cut surface of the stump should be lightly coated; herbicide does not need to be dripping off the stump.

"When mixing glyphosate, you should also add ammonium sulfate (AMS) to your mixture," advised Shank. "The pH of water in the St. Louis area is between 9 and 10. This high pH level breaks down the glyphosate in a matter of hours."

Once bush honeysuckle is gone, what are some good ways to get green back into a yard? "There is a whole suite of native plants that are great to replace it with," said Shank. She suggests American beauty berry, fragrant sumac, vernal witch hazel, wild plum, and choke cherry to name a few. An excellent source of native plant alternatives can be found at http://grownative.org. These plants will also be far more beneficial to native wildlife than the exotic bush honeysuckle.

Homeowners can win the war against the invasive bush honeysuckle, and now is the perfect time to attack it. For more information on controlling bush honeysuckle, go to mdc.mo.gov/node/5411%20.