By Heather Kolich, Agriculture and Natural Resources Agent
I find weeding therapeutic. It gets me outside into sunshine and fresh air. I can wave to neighbors and listen to birds as I make visible progress in cleaning up a garden bed or area of lawn. And since my family moved over the winter, weeding is a journey of discovery about our new landscape.
While the front yard was well maintained, the back is almost entirely a “natural” forest split by a small creek. I merrily pulled up winter annual weeds in the shade bed margin between lawn and woods, readying the beds for a 3-inch deep layer of mulch that will help smother out summer annual weeds.
One step deeper into the woods, however, I encountered three nonnative invasive plants that pushed my integrated pest management strategy to a different level.
Certain invasive plants are easily detectible during winter, so I already knew I would have to wrangle with two problematic species. Privet (Ligustrum sinense) and nandina (Nandina domestica) stay green in the winter while other plants are dormant and leafless. While weeding, I encountered small nandina shrubs in the shade beds. Beyond the beds are thick, impenetrable blocks of large privet bushes.
I didn’t notice the third invasive plant until the weather warmed a bit and sent snaking along the ground. Identifying this plant took some time and effort because it’s dimorphous; the leaf has a different shape during rapid growth. In this case, most leaves looked like perfect, miniature oak leaves growing opposite each other on a red vine. After a lengthy search, I identified the plant as Japanese honeysuckle (Lonicera japonica), which we usually see with oblong, lobeless leaves.
Several factors make these plants problematic: They grow in both sun and shade; they reproduce from both roots and seeds; they spread rapidly; and they destroy the natural biodiversity of southeastern U.S. forests by displacing native plants. Japanese honeysuckle occurs more commonly than other nonnative invasive plants, but nonnative privet has taken over 644,317 acres of Georgia forest lands.
Controlling invasive plants is a lengthy process that begins with identification. To achieve success, we need to know the lifecycle of the plant and understand how it spreads. Because privet and nandina spread by root suckers, simply cutting down the plants doesn’t eliminate them. Eradication requires a combination of mechanical removal, timely application of appropriate herbicides, and persistence through multiple seasons.
To ensure the safety of other plants and the creek, I’ll use a very targeted approach to each of these invasive plants. One component of my integrated pest management strategy involves pruning flowers and berries off the invasive plants to prevent seed distribution.
In a second component, after suiting up in the appropriate personal protection equipment, I’ll cut the stem or trunk of the plant close to the ground and immediately paint the stump with a 20% solution of glyphosate.
This application method eliminates the possibility of herbicide spray drifting to non-target plants. When glyphosate is applied to the stump immediately after making the cut, the plant pulls it down into the root system, where glyphosate works to kill roots. The dead roots won’t be able to push up suckers, but surviving root sections still can. The third component of my invasive plant eradication plan is vigilance and persistence.
If I consistently apply this plan, I expect to see progress this year and eradication in three years. At that point, my IPM strategy will focus on preventing a reinvasion of these plants through cultivation activities, including reintroducing desirable native woodland plants.
If you have a weed problem you want to tackle this spring, contact your county Extension office for assistance with weed identification and developing a comprehensive weed pest management plan.
Heather N. Kolich is the Agriculture and Natural Resources Agent for the UGA Extension Forsyth County.