The problem with learning about invasive plants species is once you know about them, you start to see them everywhere. It can be a little depressing. How joyous it was when I began my life in horticulture. Learning about amazing plant processes and all the wonderful plants used in the ornamental landscape. Indeed, at the outset of my botanical life, all plants were good.
In practice, things are quite different. My understanding of the term 'invasive' took shape after learning my first legally invasive plant – bush honeysuckle.
Bush honeysuckle describes a family of shrub-like honeysuckles. The most common invasive honeysuckles in Illinois are Tartarian (Lonicera tatarica), Amur (L. maacki), and Morrow (L. morrow). These plants hail from Europe and Asia and were once recommended for planting as ornamentals, for wildlife cover and food, and erosion control.
“Yet, landowners and researchers have now discovered, these non-native bush honeysuckles are a poorer quality wildlife food source than previously thought. Today, bush honeysuckle is considered one of the biggest threats to our native Illinois ecosystems.”
Bush honeysuckle can be identified due to their opposite leaf arrangement, white spring flowers along the stem, and pairs of typically red fruit in the fall. The center of the stem is hollow, whereas Illinois' single native honeysuckle species has a solid stem.
The best way to find bush honeysuckle is to look into the woods in the late fall or early spring where it can form dense thickets. Honeysuckle can survive in full sun or the shade of a woodland understory and it is the first to leaf out in the spring and last to drop its leaves in the fall. The shrub and herbaceous understory of woodlands vanish under the blanket of honeysuckle leaves. Leaving behind bare soil that washes into stream and rivers, choking out aquatic life. Overstory trees are not immune to the effects of bush honeysuckle. Research has shown that large tree in forests invaded by bush honeysuckle are stunted by as much as 40 percent!
Depending on the situation, there are different methods to control honeysuckle. Mechanical control using a saw or loppers to remove stems triggers vigorous growth and is often unsuccessful unless repeated multiple times a year, for many years. Some woodlands are so overgrown with bush honeysuckle, a person cannot even walk through the forest. In this case, most landowners use a skid steer or tractor with a brush clearing attachment. They then wait for the flush of new growth and can then walk through and spray the new growth with an herbicide.
In most situations, a landowner will turn to herbicides to control bush honeysuckle. Many use the cut-stump technique, where one person cuts the honeysuckle six inches from the ground and a second paints the stump with a 20 percent concentration of glyphosate herbicide. The second option is a foliar spray with a 2 percent concentration glyphosate solution. Either technique is best performed in the fall when the plant is sending energy to the root system and bush honeysuckle is one of the only shrubs with leaves making it easy to identify. Unfortunately, once you learn this plant you'll start seeing it everywhere.
There is a lot more when it comes to controlling bush honeysuckle and promoting native understory plants. Contact your local Extension office for more information on invasive plant species.