We posted an animated video on YouTube showing how to kill a weed tree using foam herbicide. The video also explains why foam herbicide works better than liquid herbicide for cut stump applications.
Invasive vines can really take over. They primarily crowd out desirable species by shading them, but they can also girdle stems of desirable plants and cut off the free flow of plant sugars to the canopy.
To control them with herbicide, there are several things to keep in mind. First, a foliar application to vine foliage is almost always a bad idea. Usually the foliage of the vine is too intermingled with the foliage of desirable plants. Even if you can segregate the foliage of the invasive from the desirable, spraying upward where vines grow is inadvisable. You will likely end up with more spray mist on yourself than on the target vine.
Second, don’t pull the vine down from the canopy. If you do, you may do more damage to the desirable plant by breaking branches and tearing into live plant tissue (if the vine has adhesive pads that attach to stems). Focus your efforts instead on killing the vine and leaving it in place. If you want to speed its decay and to lessen strangulation of a desirable plant, cut notches into the vine stem. Again, avoid cutting the desirable plant.
Third, you will probably have better luck killing the vine if you apply the herbicide in late summer, fall, or even winter. Those are the times when the plant is translocating sugars to the roots which is also where you want the herbicide to flow.
If you want to prevent the vine from producing seeds, here is a trick that I use. After the vine has leafed out but well before it has produced fruit or seeds, cut the vine as high as you can from where it is rooted. Then allow the vine to regrow. It probably will do so vigorously with multiple new sprouts from near the cut. The trick is that you will do your treatment below this cut and new sprouts. This not only should prevent the vine from flowering and producing seeds, it will also sap the roots of energy and make the herbicide application more effective.
One way to apply herbicide is to use what is called a cut stump method (shown above). With this method, you cut the stem of the vine close to the ground – generally two to four inches above the ground from where the vine is rooted. (if the vine is rooted in multiple locations, you will need to cut and treat near each root clump.) Don’t cut so close to the ground that dirt gets on the cut face of the stump (dirt neutralizes herbicides such as glyphosate). But don’t cut too high because the treatment will be less effective. Then immediately treat the stump face with a concentrated foam herbicide. Apply the foam herbicide in a ring near the outer perimeter. You want to make sure the herbicide contacts the living plant tissue called the cambium which is just inside the outer bark. Green Shoots Foam Herbicide works great for this because you can precisely stack the foam right on the cambium and it will slowly soak in. If you wait more than about 10 to 15 minutes after cutting the stump, I would recommend re-cutting before applying the herbicide. Plants seal off wounds surprisingly quickly and this reduces the effectiveness of the herbicide. Follow the instructions on the label for the herbicide and the dispenser.
Another method is a frill treatment. With this method, you scrape or cut away some of the outer bark to expose live, inner bark as shown in the photos above. This method work especially well if the vine stem is horizontal because it provides a better surface on which to apply the herbicide. If you can try to remove bark from around the perimeter of the stem. Again, Green Shoots Foam Herbicide works great for this because the foam will cling to the frilled tissue. (Liquid herbicides on the other hand will drip right off.)
Be sure not to get herbicide on desirable plants. I even avoid getting herbicide on the outer bark of desirable plants. Although you may read that water-based herbicides won’t penetrate the protective, waxy layers of cork, it makes sense not to risk harm.
You have an unwanted tree growing vigorously in the wrong place – in the middle of a flower bed or in a native grass planting or next to a building foundation. You know you need to remove it. Winter is actually a great time of year to do this. Herbicides work fine in the winter if applied correctly. See Reinartz 2002.
If you simply cut the tree or bush down, you will soon get something far worse in the spring: a multi-stemmed bush like the one shown below on the right side.
There is a simple way to prevent this from happening: use the Green Shoots Foam Herbicide System to precisely apply a concentrated herbicide to the stump immediately after cutting to kill the stump. So here is what you do.
- Cut back the tree or bush – If it is a big tree or bush, I typically cut off the upper branches first and leave a tall stump anywhere from knee to shoulder height. Clear out the branches so you have room to work.
- Prepare the Foam Herbicide Dispenser according to the instructions. Be sure to read the herbicide label.
- Cut the stump close to the ground – try to cut it within 2 to 4 inches of ground level.
- Immediately apply the foam herbicide to the cambium layer of the stump. This is a thin layer of live inner bark just inside the outer bark.
The Green Shoots Foam Herbicide System has several advantages over standard herbicide sprays:
- Precision – This is critical when you are applying to the narrow ring of live inner bark less than 1/10 inch thick. With a liquid spray, the application is so imprecise – you may miss your target. At the very least, you will waste herbicide trying to hit the target.
- Less Drip – The foam herbicide sticks to the target and will slowly soak in. Liquid sprays will bead and drip off the target.
- Visibility – the foam is visible for some time after the application. This helps in identifying what part of the target you have treated.
For more information about the Green Shoots Foam Herbicide System, visit the Green Shoots website.
Post contains content updated on August 20, 2018:
I remind people every year that late summer and fall are great times to apply herbicides to kill perennial invasive plants. I have discussed the timing of herbicide applications in several previous posts. So, get out and enjoy that cooler weather (it will come) and, for those of us farther north, beautiful fall colors!
In terms of priority, I would put perennial weeds into three groups for purposes of application timing: First are the perennials that need to be treated before a frost. Plants such as bindweed, crown vetch, and Japanese knotweed, die back after a frost. Therefore they need to be treated in late summer or early fall before a killing frost.
Second are the plants such as perennial thistles. Canada thistle is a prime target. Canada thistle can be treated a little later in the fall because it is more frost tolerant. In fact, this frost tolerance can be used to your advantage. If nearby desirable plants have died back or lost their leaves, you can apply herbicide to the thistle with less potential for damage to the desirable plants. Just make sure you apply the herbicide to foliage that is still green.
Third are the woody perennial weeds. These can be treated with cut stem or frill treatments from the fall into late winter (just do it before warm temperatures start pushing plant sugars up to the branches for leaf out). The application should be into the vascular system of the tree or shrub, e.g., cut stump, frill, or injection. The Directions for the Green Shoots Foam Herbicide System show how to do these applications.
You can also do foliar applications to woody perennials in the late summer and fall. Timing can be a little tricky: if you have had a drought, the leaves of the weed tree may be sparser and may not absorb the herbicide as well.
Green Shoots sells concentrated glyphosate in quanitites that are ideal for homeowners who are tackling woody brush or weed trees. We sell a 16 ounce bottle of concentrated glyphosate (41% active ingredient). Many stores sell what they call concentrated glyphosate. Don’t be fooled. Usually the concentration is well under 20%.
Especially if you are doing cut stump or frill treatments, a concentrate is essential. Glyphosate works well on plants in a concentrated form. It is almost like a quarterback blitz – glyphosate works better with a quick rush than with steady pressure. That’s why you need the concentrate.
Feel free to contact me with any questions. Just go to the Green Shoots website for contact info.
Fall is generally the best time to control perennial weeds. Perennials are moving sugars from above-ground sinks – in particular foliage – to underground sinks – rhizomes and roots, for example. for overwintering. In order to kill perennial weeds, these underground sinks must be destroyed.
Fall offers other benefits as well – cooler weather, less dense foliage, and fewer bugs!
What is the best way to kill invasive perennials? Several rules hold. Apply herbicide only to living tissue. Perhaps that’s obvious. That can be green leaves or stems or vascular tissue.
Since most people are probably least familiar with vascular treatment methods, I will discuss those. Photos above show each of these methods step-by-step. One method is to do a cut stump application. With this method a weed tree is cut down and herbicide is applied to the cut-surface of the stump. For most homeowners who used water-based herbicides, you should apply the herbicide soon after the cut is made. (There is debate about how soon but I try to do it within a few minutes if possible.) Two keys to this method are: first, make the cut as close to the ground as possible (e.g., 2 to 3 inches if possible); second, make sure you apply herbicide to the outer edge of the stump just inside the bark. This will ensure herbicide gets introduced into the phloem which will carry the herbicide into the root system. The Green Shoots foam herbicide system works great with this method because the foam stays on the cut-surface and doesn’t drip down the sides of the stump.
Another method is a frill application where the tree is left standing and cuts are made into the bark of the tree. Use a knife or chisel on smaller trees and a hatchet on larger trees to make the cuts. Apply herbicide to the exposed vascular tissue. These cuts should be made as close to the ground as possible. Of the two methods, I find the cut-stump method to be the most effective. However, the frill method probably takes less work especially when you are dealing with big trees.
For green-stemmed perennial weeds, I use a slightly different method. I bend the stem near the ground and apply the herbicide at the bend. For some reason, this method works better than just cutting off the stem. I don’t know why. The Green Shoots foam herbicide system works especially well with this method because the foam sticks tightly to the bend in the stem unlike methods that use liquid herbicide. This technique can be often be used even after the leaves are nipped by frost as long as the stem is still green.
For all these methods, use a concentrated herbicide mixture. For example, if I am using a glyphosate-based herbicide, I typically use a concentration of about 35 % active ingredient.
There are a number of benefits to these methods of application. First, they are very effective. I typically have a 100% kill-rate using the Green Shoots foam herbicide system with these methods. Second, they protect the environment. The methods allow for very targeted applications. And with Green Shoots foam, the herbicide sticks well to the target surface and very little drifts through the air or drips off onto other plants.
Treating a tall weed with herbicide or weed killer can be a challenge – especially if the target weed is near desirable plants. Conventional sprays are difficult to control. Fine droplets are hard to see, so it is difficult to know what you are treating with the herbicide spray. Moreover, the fine droplets in sprays have a tendency to drift. And, when the droplets do land on the target weed, they may bead and roll off the leaf.
This video shows an application to a perennial thistle using the Green Shoots Foam Herbicide System (link to video). Note how precise the herbicide application is – without drift, drip, or off-target spray. Toward the end of the video you can see the results where the weed has dead fifteen days after treatment.