Growing up in the South, I learned about invasive plants early. Near the airport was an alien landscape of towering green monsters created by kudzu. Known as the ‘Godzilla’ of the plant world, it climbs in thick masses up and over trees, and covers houses and barns, open fields and hillsides. Believe it or not, at the right time of year, you can actually see kudzu growing. Under warm temperatures and good moisture conditions, it has been clocked growing nearly 3 feet in one day! Even now, it still dominates woods all over the South, decades after the last kudzu was intentionally planted for erosion control and after governmental agencies and private property owners alike have spent huge amounts of money and effort to remove it.
Growing like a Weed
The easiest definition of weed is simply ‘a plant out of place,’ basically any plant growing where it is not wanted. ‘Noxious weed’ is the term for a particularly nasty, hard-to-control pest plant. An ‘invasive exotic species’ is any vicious, aggressive imported plant or animal. ‘Exotic,’ in this context, simply means that a plant is not a native species.
When taken out of their usual communities, natural control agents are often left behind and exotic plants become weeds that can spread like wildfire. Here in Missouri, minor problem plants include teasels, giant fescue, wooly mullein, ox-eye daisies and Queen Anne’s lace. They are so totally integrated into the landscape that it would be nearly impossible to eradicate them. Familiar to all as an invasive exotic weed is the vining Japanese honeysuckle (Lonicera japonica), which scrambles over the ground consuming everything in its path. Other seriously aggressive plants in our region are the bush honeysuckles (Lonicera maackii and L. morrowii), garlic mustard (Alliaria petiolata) and Euonymus.
Lonicera–The Lolita of The Landscape
Our worst local plant invades by stealth and beguiling beauty. It was first grown for its sweet flowers, bright berries, interesting bark, supposed soil erosion control ability and long leafing. Introduced before 1900, bush honeysuckle came into wide usage in the suburban expansion of the 1950s and ‘60s as a popular privacy-screen plant.
The biggest problem now is that most people are still captivated by its beauty and not educated to its dangers. We did not know 50 years ago how devastating these plants would be to our local biodiversity as they multiplied rapidly in the natural environment. And we don’t have to go far to see this menace in action, as the epicenter of the Missouri epidemic may actually be in Ladue!
Destruction of native ecosystems
Favoring woodland edges, road cuts and waterways, bush honeysuckle colonizes rapidly. Once established, it snuffs out native wildflowers, herbs, shrubs and tree seedlings by leafing out early in the spring, before anything else does, and holding its leaves late in the fall. This constant shade makes it very hard for native plant seedlings to grow and results in solid stands of honeysuckle. The shallow root systems also steal much of the available water. Even tree seedlings are unsuccessful in growing through these dense thickets, so areas that are wooded now will become open as older trees die and no new ones can survive.
Another reason for the desolate honeysuckle landscape is allelopathy, the phenomenon where a plant produces chemicals that inhibit the growth of other plants around them. Both the roots and leaves secrete toxins, with the highest concentrations in the leaves. Leaf litter on the ground over the winter suppresses future plant competition. And studies have shown that even if a plant does manage to grow under honeysuckle, it will be significantly smaller, bloom later and produce less seed. Eventually, you’re left with nothing but honeysuckle. The final insult to biodiversity is the heavy bloom of honeysuckle thickets that draw the attention of pollinating insects, so much that many of our native species with similar bloom times do not get their flowers pollinated at all and seed set is drastically reduced.
When Lonicera becomes abundant, the whole composition of woodlands and forests is affected and local populations of wildflowers, understory species, birds, bees and even canopy trees will be threatened. In the end, a monoculture of honeysuckle is an environmental disaster.
Invasive Plant Leafs-out Early
One of the easiest ways to identify bush honeysuckle is by its habit of leafing out very early. Now is the time to mark plants for future eradication. The leaves are in pairs closely placed to the stem. Later in spring, familiar white and yellow flowers line the arching branches in neat, double file rows. In autumn, the berries are a bright clear red.
Gaining the Upper Hand
Bush honeysuckle can be controlled by prescribed fire (not an option in urban areas) or by cutting and treating stumps with selective herbicide. Pulling out young seedlings is easy when the soil is damp, but removing established stumps leads to soil erosion problems. Just let them re-sprout and treat again with herbicide. Recent scientific studies using lance-style herbicide injectors show good control, but these are prohibitively expensive for homeowner use.
Biodiversity and the Backyard Birder
Marguerite Garrick, an active member of the Gateway Cooperative Weed Management Area, says bush honeysuckle has “a strong negative impact on migratory birds.” Planted originally as an attractive food source for birds, it actually lacks the nutritional value needed for the long flights of migratory birds. Birds eat it like junk food and then drop the seeds down fence rows and through woodlands, contributing significantly to spread. She reports that in monitoring areas where all bush honeysuckle has been removed, there has been a noticeable increase in the bird population.
Biodiversity Preservation Begins at Home
When my husband, Peter, lectures on the great value of biodiversity and the increasingly severe threats to it, many people ask what they can do to help preserve it. One of the most important ways everyone can help is to begin in their own backyard. Be a good neighbor and responsible Earth steward by removing bush honeysuckle from your own property. Our world will be better for it.
The War on Honeysuckle
• Mark plants NOW with tagging tape as they leaf out and are easy to identify. If you are not sure about identification, bring a sample in a sealed baggie to the Plant Doctor desk at the Missouri Botanical Garden Kemper Center (10 a.m. to 3 p.m., Monday through Saturday).
• Make your action plan to remove and replace vegetation as needed, order mulch and new shrubbery and check local garbage rules and schedules.
• Assemble the artillery: Collect compound-action, fiberglass-handled loppers, a small pruning saw, a light duty chainsaw, herbicide and applicator, dye or food coloring to mix with herbicide for marking, and an energetic volunteer to help you.
• Time the assault: Now is the best time to launch into battle because the plants are easy to identify by their early leaf out.
• Commence the attack: Cut stems near the ground, leave stumps in place. Paint with 20- to 25-percent solution of RoundUp or similar product within an hour of cutting. Tint the herbicide with dye or food coloring so you don’t miss any stumps.
• Don’t Retreat, Re-Treat! Spray any stumps that re-sprout when the shoots are soft and tender. They absorb herbicide more easily at this stage and one or two reapplications will kill even the most stubborn.
• Replant areas that were heavily infested with Lonicera will be nearly barren of other plants. To prevent soil erosion, mulch bare areas and replant with suitable alternative shrubs and groundcovers.
• Prevent Reintroduction by annual inspection, Watch for new seedlings: knee-high sprouts are easy to pull out on wet days
• Form a neighborhood Honeysuckle Hunter brigade to help educate others about the problem and how to identify Lonicera. Enlist energetic young people from Scout troops and church groups to help elderly residents clear their properties. Cooperative action by whole communities can reduce the seed bank for reintroduction.
Lucky to Live in Ladue
• The Ladue Garden Club has tackled this problem with enthusiasm and virtually eliminated Lonicera from Rhodes Park as they have worked to develop rain gardens along the Deer Creek tributary that runs through the park.
• Another great citizen effort is the Deer Creek Watershed Friends group. According to chairman Rick Holton, “both bush honeysuckle and euonymus are in our gun sights.” Shallow-rooted honeysuckles contribute to erosion along stream banks and reduce down-stream water quality. The group is recruiting volunteers to join in a Deer Creek Clean up on April 25 for the City of Ladue. There are already 45 Creek Captains to facilitate clean-ups on nearly every stretch of creek in the City of Ladue. Sign up at deercreekfriends.net/day-of-service-sign-up.
• City residents may have their honeysuckle debris hauled away at regularly-scheduled spring pick ups. The branches are taken to Edie’s Mulch Pile where they are shredded and converted to mulch. The mulch is then available to for pick-up or home delivery for a modest fee. Call Ladue Public Works at 993-5665 for more information.
Helpful Web sites:
Grownative.org has great replanting ideas using native Missouri plant species.