Oh, the weather outside is frightful, but removing invasives feels so delightful

by | Feb 15, 2024

Though the long nights, short days and dropping temperatures may tempt you to stay indoors, winter is an optimal time to accomplish some important things on your property. Many management practices can be implemented during this time of year that you’ll be thanking yourself for doing come spring. Winter is a preferred time to conduct prescribed fire operations in the Southeast providing a reduced risk of damage to desirable timber and a larger window of days with favorable weather conditions. A dormant season prescribed fire will not only knock back undesirable woody stem encroachment, but it can also reduce some fungal diseases such as Heterobasidion root rot (formerly known as annosum root rot), Tubakia leaf spot and brown spot needle blight. Prescribed fire helps remove the infected leaf litter and the fungal inoculum, or any part of the pathogen that can cause infection, thereby lessening the likelihood of infection the following spring. Seek advice from a forestry professional to determine if burning is suitable for your property.

Oriental bittersweet can be easily recognized from fall through winter by the bright red, berry-like fruit with yellowish-orange outer skin.

Invasive Japanese honeysuckle (left) compared to yellow jessamine (right).

The increased visibility due to dormant vegetation during winter also presents a strategic opportunity to rise and reclaim your property from those invasive vines and woody species that have invaded your land and now stick out like a sore thumb. These unwelcome guests can disrupt the balance of your landscape. Often, their presence deters certain wildlife, creating a domino effect that impacts food webs and leads to shifts in forest composition. Invasive vines like Japanese honeysuckle (Lonicera japonica), oriental bittersweet (Celastrus orbiculatus), English ivy (Hedera helix) and Chinese Wisteria (Wisteria sinensis) can choke out trees, eventually killing them by blocking out sunlight. They can also weigh down trees, making them more susceptible to damage. Invasive trees and shrubs such as Bradford pear (Pyrus calleryana), thorny olive (Elaeagnus pungens), autumn olive (Elaeagnus umbellata), multiflora rose (Rosa multiflora) and Chinese privet (Ligustrum sinense) displace and aggressively outcompete native plants for space, light, water and nutrients. Japanese honeysuckle and less established shrubs can be hand-pulled after rain while the soil is still moist. For more mature vines that have become established and grown into the canopy, the most feasible approach is cutting. Using a good pair of pruning shears, loppers or a handsaw, cut each vine in two places, at ground level and then at eye level. This method is referred to as a “window cut.” After cutting, resist the urge to pull down the vines as this poses a safety risk to you and may also damage the tree. The upper portion of the vine has been severed from their source of nutrients and will die and decompose in time.

Glyphosate solution with an indicator dye added to the outer edge of a stump greater than 4 inches in diameter. Photo Credit: Miller, James H. U.S. Forest Service, Southern Research Station.

Immediately after cutting, apply a solution of glyphosate or other recommended herbicide to the root stump to prevent regrowth. A spray bottle sold at most garden and feed stores, or a sponge applicator can be used for this method. For stems less than 4 inches in diameter, herbicide can be applied to the entire top of the stump. For stumps greater than 4 inches in diameter, it is only necessary to apply herbicide to the outer edge. As an alternative, a foliar herbicide can be used several weeks later on the regrowth. If you’ve chosen to use a foliar herbicide, give it time for new shoots to emerge before applying. Treating too early will only defoliate regrowth. The best practice is to wait about six to eight weeks, allowing new shoots to mature enough to absorb and transport the herbicide down to the roots, finishing the job. If you prefer not to use an herbicide, make your lower cut around 1 to 2 feet from the ground. Keeping in mind that the stump will send out new shoots, continue to remove all regrowth as soon as you see it. This will eventually exhaust the root system and kill the vine.

Proper disposal is critical to the control process. If leaving vine material to dry and decompose, consider placing it in an area without access to soil. Avoid composting unless you are certain there is no living plant material remaining. Basal bark treatment, hack and squirt, girdling, cut stump herbicide treatment and hand pulling are all effective methods for controlling invasive trees and shrubs. A basal bark herbicide treatment can be used for stems with a diameter at breast height (DBH) of 6 inches or less, or shrubs with multiple stems. For some, this is the preferred method because it requires no cutting. An oil soluble solution typically containing triclopyr and carrier oil to aid penetration is sprayed 18 to 24 inches from the bottom of all stems and any exposed roots. The bark should be thin to be most effective. You can test this by scraping the bark with your fingernail. The plant is a good candidate for basal bark treatment if the tissue beneath the bark layer is slightly damp and has a greenish hue.

Hack and squirt demonstration. Photo Credit: Cody A. Lastinger and Stephen F. Enloe, University of Florida.

Hack and squirt is a method of making small, angled cuts into the bark and applying a glyphosate, triclopyr or other recommended herbicide to trees and shrubs to kill them. The cuts should be closely spaced and angle downward to create a well. The tree absorbs the herbicide and dies over time. Similar to the hack and squirt method, girdling can be achieved by using a small hatchet or saw to cut a ring all the way around the trunk of a tree or shrub, removing a band of bark to expose the vascular tissue, thereby cutting off the plant’s nutrient supply. Herbicide can be applied to the wound immediately following the cut. While methods like girdling and hack and squirt are cost-effective, they’re not advised for large trees in public areas or near infrastructure. These methods kill the plant over time and when the tree eventually falls is unpredictable. Adding an indicator dye to your solution is good practice because it helps track what has already been treated. Remember to treat cuts within 5 to 10 minutes for best results as waiting too long will allow the wounds to dry, significantly decreasing herbicide penetration.

These methods give you the upper hand against tackling invasive vines and woody species during winter as your application is focused precisely where needed, significantly reducing the amount of herbicide used and sparing nearby plants from unintended harm caused by drift. Think of it this way: treating a stump, a precise squirt to a tree base or a downward cut, requires far less herbicide than blanketing an entire leafed-out shrub with a foliar spray. Right tool, right gear, right amount – remember, always use pesticides as described on the label. The label is the law. Select an herbicide that meets your objective, wear the appropriate PPE and always follow the labeled recommendations or have a licensed herbicide applicator do the work. If you prefer not to use herbicide, a plant extracting tool is recommended on shrubs and small trees around 3 to 5-feet-tall with a DBH of up to 2 inches. Make sure to remove the entire root for this to be effective. Girdling is also an option on woody species with larger stems, but results will take a little longer.

If this post hasn’t motivated you to leave the comforts of your warm abode, consider reclaiming your property from those invasives Friday, March 1, by joining the N.C. Forest Service, N.C. State Parks, N.C. Native Plant Society, N.C. Botanical Garden and many others for the inaugural statewide Weed Out Day during National Invasive Species Awareness Week. See the Forest Health Program’s Invasive Plants page for more information on invasive plant identification and specifics on treatment recommendations. For recommendations on treatments and herbicides, contact your local N.C. Forest Service county ranger.

 

References:

Grover, A. (2023, Nov. 8). ’Tis the season – winter invasive plant control. Pennsylvania State University Extension. https://extension.psu.edu/tis-the-season-winter-invasive-plant-control#:~:text=You%20can%20stem%2Dtreat%20non,with%20oil%2Dsoluble%20triclopyr%20products.

Reinartz, J. A. (2017, September). Winter is an excellent time to control invasive shrubs using the “Cut Stump” method. UW-Madison Extension Forestry. https://woodlandinfo.org/wp-content/uploads/sites/383/2017/09/POOP-1.pdf