Updated: January 21, 2021
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. 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 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. In winter, 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).
Freshly cut stump of weed tree
Foam herbicide applied to cut stump in winter
How late in winter can you apply? Read our other post on applying brush killer in late winter/ early spring.
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!
In this piece we identify the key advantages of our new ultra-low pressure electric dispenser (patents pending). (See also this YouTube video: Electronic Dispenser Dispenses Herbicide with High Precision.)
First, when used as a sprayer (i.e., for spraying liquid drops), ultra-low pressure (i.e., less than about 15 psi) offers key benefits. The biggest is less off-target spray. We did indoor testing in 2016, where we sprayed colored water on white paper using a Hypro(R) 30HCX8 hollow cone nozzle. We sprayed at a variety of psi’s. What was particularly striking in these tests was how far the spray extended beyond the primary spray band at higher pressures. At 30 psi, the spray band extended at least 30 inches beyond the center-line! This was an indoor test with no wind. At 9 psi the “shadow spray band” only extend 15 inches. This means, if you are spraying at a high psi, you are doing off-target damage to desirable plants and wasting a lot of expensive herbicide.
Second, ultra-low pressure places far lower demands on the pump and battery. This means our electric sprayer can be far lighter than the competition. Other electric systems typically weigh well over 15 lbs. Ours, even with the fully padded backpack frame, weighs about 10 lbs.!
Third, ultra-low pressure makes great foam! For example, you can hook up our foam-making attachments with the mesh brush. Use it to wipe foam herbicide onto foliage or onto stumps. As shown below, you will get high precision, no drippage (like you do with conventional wiping systems), and extended absorption of the herbicide into the weed’s vascular system because the foam keeps the herbicide in liquid form longer. (Here’s a YouTube video: Cut Stump Treatments)
We will be producing a limited quantity of our Ultra-Low Pressure Electric Dispenser in the first year (2017). We are primarily selling it to professionals with a strong need for the benefits offered by the system. Please contact Green Shoots for availability and pricing!
Our new dispenser works great for doing basal bark applications of herbicide.
Basal bark treatments involve the application of an ester herbicide in an oil carrier to the bark of a tree. We actually dial the pressure in at 2 psi – i.e., very low! This produces a narrow stream of herbicide that can be precisely applied even to very small stems such as the one shown below. This reduces off-target harm and reduces herbicide waste. We posted a YouTube video that goes into greater depth.
Green Shoots will be offering a new electric sprayer in 2017. The sprayer will operate on ultra low pressure. This has lots of advantages including more precision and less off-target spray. This is especially important when spraying herbicides because off-target spray can harm desirable plants and waste expensive herbicides. The battery will last for a full day. The sprayer can also easily be converted into a foam dispenser. The sprayer will have all sorts of other great features, many of which are shown in the following photos.
The pressure can be adjusted in increments of 0.2 psi and from 1.5 psi to 12 psi. Pressure from about 1.5 psi to 10 psi works great for dispensing foam. Pressure from about 5 psi to 13 psi works great for spray. Green Shoots will also offer a very comfortable backpack frame with a hip belt.
Remember with this electric sprayer there is no pump lever, so one hand can hold the spray wand and the other can be free. Elimination of the pump lever also makes it much easier to maneuver in thick brush.
We are testing our latest innovation – an ultra-low pressure sprayer. It can operate at under 10 psi.
Ultra Low Pressure Electric Dispenser
Spray pattern shows evenly spaced droplets
What are the advantages of ultra-low pressure? First, there is less drift. That’s because the ultra-low sprayer consistently produces medium size drops, not the very fine, drift-prone drops. Second, the drops from the ultra-low sprayer travel slower through the air. This means that the drops are less likely to bounce off the foliage of the target weed. Finally, the ultra-low pressure sprayer uses very little power. This means the sprayer can be lighter and still operate for a long time on a single charge. Here’s a video of ultra low pressure sprayer demonstrating the new dispenser.
We are offering a new product: a Stump Killer (see product). This product can be used right out of the bottle, i.e., no mixing required. It is perfect for those with a small number of weed trees to control. Here is our video explaining how to use it:
Here is a link to the video: How to Kill a Tree Stump Fast – 5 Tips.
We launched our new website! Please take a look: Green Shoots.
New Website Home Page
Check out our newest video How to Kill Invasive English Ivy Vines: 3 Steps. If you like PowerPoint presentations better, here it is: PowerPoint How to Kill English Ivy Vines. We will be publishing another set of presentations on killing English ivy groundcover. For that we recommend a foliar or wipe application. English ivy can be a real problem in many parts of the world. It can climb tall native trees and eventually even kill native trees. As a groundcover, it also can out-compete natives. One thing: English ivy can be controlled in the winter when many native plants are dormant.
At Green Shoots, we sell concentrated weed killer and our foam herbicide dispenser systems help you
apply that weed killer precisely and with low drift. Concentrated weed killer or herbicide is not just more economical. It is also more effective.
Read this paper (link) from Bryan Young, currently a professor at Purdue about glyphosate rates. In it he says: “The most consistent application factor that can increase glyphosate efficacy is lower carrier volumes.” What does Professor Young mean by this? He means that by adding less carrier (i.e., water) and increasing the amount of glyphosate herbicide (i.e., increasing the herbicide concentration) in the spray solution, the herbicide is more effective. Moreover, this is the case even though an application may cover less of the target plant.
Take a look at the photos below and this video to see before and after images of weeds treated with low volume/high concentration applications: Video (link). As you will see in the foliar applications, very small amounts of herbicide are applied to very small areas of foliage (probably covering less than 10% of the green foliage). In spite of the small amount of coverage, the weeds were completely killed.
Concentrated Foam Herbicide Applied to Bull Thistle Rosette
8 Days Later – Thistle Is Dead
This presentation at the Upper Midwest Invasive Species Conference, 2014, summarized some of our control work on invasive knotweed at Southwood Nature Preserve in
Foam Stream Targeting Invasive Knotweed
the Twin Cities Metro area. It also briefly discusses use of our foam herbicide system by the Northeast Iowa RC&D where they have had success treating a large infestation of greater than 25 acres. Finally, Washington State
Foam Herbicide Clinging to Knotweed Leaves
University did some testing this summer comparing our foam herbicide dispenser to traditional spraying techniques. So far (and these results are very preliminary), the foam herbicide has performed better than the spray even though half as much herbicide was used on the plots where foam was applied. The full presentation is online at: How to Kill Japanese Knotweed.
As soon as we get data from Washington State University on their testing of the foam system, we will provide a link or other information.