Summary
Coverage
Image showing typical coverage from spraying glyphosate foam from the Small Herbicide Foam Dispenser.
Comparing Herbicide Concentrations
Treatment areas where four, five, six, and seven percent active ingredient glyphosate foam were sprayed onto patches of crown vetch are shown and discussed.
Application to Individual Stems
Images and discussion of a test application of glyphosate foam to individual stems in a higher quality area.
Large Herbicide Foam Dispenser
Application areas before and after foam has collapsed are shown along with discussion about using the large foam herbicide dispenser compared to the small foam herbicide dispenser.
Other Related Blog Posts
Links to related posts on this blog are given.
Credit
The person who first gave me the idea of applying herbicide in this manner.
Coverage
The below image is an example of how much crown vetch foliage I would attempt to cover when spraying herbicide out of the Green Shoots Small Herbicide Foaming Applicator.
Comparing Herbicide Concentrations
The treatments discussed in this section were performed on 10/15/2023.
Four Percent Active Ingredient Glyphosate Foam
The below image is of a patch of crown vetch that had four percent active ingredient glyphosate foam sprayed onto it using the Green Shoots Small Herbicide Foam Dispenser. The dead stems are crown vetch that were killed by the herbicide application. There are live crown vetch shoots visible in this patch. The reduction in area covered by crown vetch was excellent but not complete. Also, notice that plants which I avoided spraying with the foam, like spiderwort (Tradescantia ohiensis), were not impacted by the application.
Five Percent Active Ingredient Glyphosate Foam
The crown vetch patch in the below image has no crown vetch sprouting up through the dead stems. Control in this patch was complete. There is some crown vetch visible in the grasses at the top of the image. I did not spray the crown vetch in the native grasses with glyphosate foam. I plan to use a different herbicide to control crown vetch where it is in native grasses or apply glyphosate foam carefully to individual compound leaves and stems.
Treated patch of crown vetch that has sprouting. Areas of it were completely killed. Possibly, I did not spray as much foam where the crown vetch is growing.
Six Percent Active Ingredient Glyphosate Foam
The patch of crown vetch in the below image has no stems emerging this spring. There is some crown vetch visible in the upper right side of the image. This crown vetch was not sprayed to avoid impacting native vegetation. Glyphosate foam will be applied to individual compound leaves and stems later.
Patch of crown vetch that also has no stems emerging. Six percent active ingredient glyphosate foam appears to be the minimum that results in complete kill.
Seven Percent Active Ingredient Glyphosate Foam
Like the areas sprayed with six percent active ingredient glyphosate foam, areas sprayed with seven percent active ingredient glyphosate foam also had compete kill of crown vetch.
There is a tall goldenrod left of the middle of the image showing herbicide impacts. It is likely I accidentally got some of the glyphosate foam on this tall goldenrod when I was spraying the foam.
Untreated Area
A patch of crown vetch that was not treated.
Application to Individual Stems
The below image is of a crown vetch plant that had four percent active ingredient glyphosate foam applied along the compound leaves using the Green Shoots Small Foaming Herbicide Dispenser. I did this as a pilot test in a higher quality area.
I put surveyors’ tape around the crown vetch treated in the above image so it would be easy to relocate later. When I checked the location on 4/21/2024 there was no crown vetch in this location and off-target damage was not visible.
I did this same method of treatment in other areas and all the crown vetch was not killed. This percentage of active ingredient and application method appears to be the threshold where control begins to occur.
Update: I visited this area again on 6/23/2024 and one stem of crown vetch was growing in the ring of surveyor’s tape. Either I must have not gotten enough herbicide on the stem in that part of the clone when I treated it last fall or this stem grew into the location from the adjacent plant (that was not treated with herbicide).
This is a difficulty of using the minimum amounts necessary to achieve control with the goal of preventing nontarget damage. The trade-off is more work later to treat what has survived.
Large Herbicide Foam Dispenser
Last December, I purchased the Green Shoots Large Herbicide Foam Dispenser.
On 4/21/2024, I was able to use it for the first time. I used it to treat individual crown vetch leaves with four percent active ingredient glyphosate foam. This in an area that was higher quality, and still has some quality plants, but now has lots of tall goldenrod.
A different area of this treatment location after the herbicide foam has collapsed into a liquid.
The Green Shoots Large Herbicide Foam Dispenser dispenses a thicker stream of foam than the Small Herbicide Foam Dispenser. When covering crown vetch leaves with the Large Herbicide Foam Dispenser more herbicide foam is applied. Since four percent active ingredient glyphosate foam did not provide complete control when I applied this foam to individual crown vetch leaves using the Small Herbicide Foam Dispenser, the thicker stream of foam produced by the Large Herbicide Foam Dispenser might give better control at this herbicide concentration.
I will mark the plants I treated when applying four percent active ingredient glyphosate foam with the Large Herbicide Foam Dispenser. This will allow me to determine if the increased amount of foam being applied gives a better application effectiveness.
Regarding using the Large Herbicide Foam Applicator, I find it to be easier to use than the Small Herbicide Foam Applicator. I like the hose provided with the Large Herbicide Foam Applicator that allows an herbicide applicator to be further away from where the herbicide is being applied. This can be helpful in avoiding herbicide fumes. However, I will still use the Small Herbicide Foaming Applicator for more careful applications in higher quality areas.
Other Related Blog Posts
Credit
The above method was adapted from how Laura Hunt has volunteers apply herbicide foam to control Sericea Lespedeza (Lespedeza cuneata) for the Southeastern Grasslands Restoration Institute.
Stewardship Chronicles 
Leave a reply to Crown Vetch Control At Hosah Park on 9/14/2024 – Stewardship Chronicles Cancel reply