Typically in May through June (starting mid-April this year) we recommend withholding use of 18-20% glyphosate (i.e. RoundUp Concentrate Plus) for cut-stump treatment of non-native invasive buckthorn. Here is why:
The cambium layer is the target area for application of herbicide in cut-stump method. The cambium layer, located next to the inner bark, transports energy from the plant downward for storage in buckthorn’s root structure. During the May through June timeframe the energy flow reverses direction to bring energy upward for leaf development and plant growth. It is during this time that application of herbicide to the cambium will have limited to no effect until full leaf out occurs and a downward energy flow to the roots resumes. During this “off” period of cut-stump treatment consider the following two-step buckthorn removal method:
Remove the buckthorn canopy by cutting stems high enough to leave adequate space for a second stump-cut in the future. This allows sunlight to reach the native species that would otherwise be shaded out by the buckthorn canopy. Return to the site in the future during a time when use of herbicide will again be effective. At the time of the second cut, cut the stump as close to ground level as possible without damaging your equipment. Without delay, apply herbicide to the cambium area of freshly cut stumps. The remaining stems from the second cut can be left in the woodland to decompose, placed on a slope to slow erosion or be mulched for ground cover. Refer to my previous blog* segment, EARTHWORMS, DUFF AND OTHER STUFF, about the importance of mulching if your buckthorn area is accessible for mulching equipment.
Another good use of time during the “off” period of cut-stump buckthorn treatment is pulling blossoming garlic mustard plants. Garlic mustard is blossoming now and it is critical to prevent more seeds from developing and adding to the seed bank. For more information about garlic mustard refer to the garlic mustard series, GARLIC MUSTARD – BANE OF MY EXISTANCE in my previous blog* segments.