When it comes to killing woody invasive plants, winter is generally the best time. This may surprise you. Herbicide labels may confuse you because labels often say the herbicide should be used when the target weed is “actively growing.”
However, cut stump and basal bark treatments work great in winter as long as the plant has an above-ground stem with live inner tissue. Weed trees and bushes all have live inner bark – the cambium layer. Therefore consider winter treatment for invasive woody species such as Asian bittersweet, buckthorn, honeysuckle, kudzu, privet, tree-of-heaven, etc.
There are a number of advantages to working in winter (or late fall):
- Effectiveness: The greatest success I have had controlling woody species is in late fall, winter, or very early spring (before sap starts flowing up the stem to the branches). This is true for others too. Reinartz 2002.
- Ease of Movement: The absence of leaves and growing plants makes it surprisingly easy to move through dense growth.
- Comfort: Removing invasives can be a lot of work, especially if you use hand tools. You can stay warm without being sweaty and uncomfortable.
- No Mosquitoes or Ticks: This is a godsend. If it’s above freezing and there’s no snow, ticks can be out but at very reduced numbers.
- Identification of Targets: As long as you can identify the invasive by the bark and structure of the plant, Identification is much easier. Without leaves blocking your view, you can see so much better.
- Cold Temps: I usually do not work when it’s below about 20 degrees F. If it gets below that temperature, water-based herbicides may freeze, especially around the nozzle. Plastic containers also become more fragile.
- Deep Snow: It is difficult to do either cut stump or basal bark treatments if the snow is more than a few inches deep. You can remove snow around the base, but this can be time-consuming.
For cut stump treatments, cut the stump as close to the ground as possible (1 to 2 inches) above ground level. (I find that failed cut stump treatments often result from cutting the stump too high.) Brush off any debris on the stump face. (Dirt will neutralize herbicides such as glyphosate.) Then apply the herbicide immediately after cutting (within 5 minutes or so).
Good luck! I hope you are able to get out on a nice warm winter day to remove some invasive plants. It can really be enjoyable!