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Wednesday, July 5, 2023

Crown Vetch - How to Combat an Evil

It's a threat to biodiversity. This menace can roll over a fine, ancient prairie or savanna, killing all - rare plants and animals alike. It's a bad plant! Really? Can a plant be "bad"? See Endnote 1. 

With its colorful but deeply ugly face, it glares at us, below:


A nightmare? But this is a story with a happy ending. We found the feared and hated killer invasive in a high quality area - near endangered species. We'll show what we did to wipe it out. But first we'll say why.
The photo above is a detail from Palatine Prairie where it was left to expand for many years. In large parts of this original prairie, as shown above, crown vetch had wiped out nearly every other plant and animal. Aside from couple of sprigs of toadflax (white flowers) and a few blades of sedge, nothing else survives.

In another photo from nearby, a few more plants survive. In the upper left corner are some blazing star and prairie dock leaves, but the trauma is shocking. Perhaps twenty plant species that would have been in this photo a few years ago are already gone, and vastly more species of invertebrates.

So what did we do (as photographed below) at Somme? After much experimentation, we've adopted a radical approach. In high quality areas, we cut most other vegetation, to save it - and get it out of the way temporarily. Think of a prairie fire in summer. Everything above ground is removed, and the prairie sprouts right back.
Here's what the patch looked like when we finished cutting away the rare beauty. Next step: we spray with Transline, a herbicide that kills mostly legumes (like crown vetch and prairie clover) and composites (like blazing stars and asters). So we especially carefully cut all the natural legumes and composites, and we also cut any other vegetation likely to get in the way of the spray. We want to coat every crown vetch leaf with that medicinal chemical. 
Next, step back for a minute to think about the context. The cut patch is in the middle with mostly prairie vegetation in the foreground and savanna vegetation near those trees. Literally hundreds of plant species here are threatened.

The open savanna or "prairie" vegetation here includes prairie lily, both white and purple prairie clovers, prairie violet, and scores more conservative plants.

The next act was to spray:
The blue is a dye in the Transline herbicide. We can see it coating every leaf. We did not successfully cut out every other plant, but we cut most of them. The bergamot and violets we see here will probably survive fine. If not they'll spread back in from around the edges. We cut them, to some degree, to save them. But we cut mostly to make sure we killed all the crown vetch.

Too many times, we had returned to a sprayed patch, years later, to find that we'd missed a bit, and the infestation was again virulent. (This approach is too demanding for larger populations, but even there, it may be helpful to use this sort of approach to save some patches of highest quality vegetation so that it and its soil biota can recolonize.)
Here, steward Eriko Kojima uses a backpack sprayer. For small patches, she often uses a little hand sprayer. 

She has done this work in very high-quality prairie ("Grade A") with complete, permanent control of the vetch, and no loss of high-quality prairie plants. For years, we repeatedly checked that spot. The crown vetch was completely gone. There was no noticeable difference between the sprayed patch of high quality prairie and the unsprayed high quality prairie all around it. 

On the other hand, we also know from experience that older patches of the vetch have years' worth of seed lying in the ground, waiting. They sprout. We watch for them and kill these smaller, isolated plants before they have time to booby trap the ground with more seed. After a few years, all but the worst populations are gone. The lesson: find it and zap it early.

This post is and update and expansion of a section of a previous post.

It would be good to hear from others about successful and unsuccessful approaches.  

Endnote 1

Biodiversity loss is a major threat to the planet. There are other evils: climate change, war, oppression of some people by others. Not all of us need to take time out of our happy lives to work hard to end all evils. But it's a badge of honor to humanity that many of us do pitch in where we can. Biodiversity is an incomparably important heritage that has evolved over hundreds of millions of years. Our species is unintentionally wiping out major parts of it. Numerically, most species and ecosystem types are threatened with oblivion or radical depauperization. 50% of the rainforest is gone. 99.99% of the original tallgrass prairie is gone. Less than that survives of high-quality oak ecosystems. Invasive species are today one of the two or three major threats to most surviving remnants. Many of us have been inspired by the words and actions of Rachel Carson, Aldo LeopoldRobert Betz, Tom Vanderpoel and many. Also, of course, there's this quote: The only thing necessary for the triumph of evil is for good people to do nothing. 

13 comments:

  1. Excluding the actual spraying with Transline (a clopyralid herbicide), removing from harm’s way desirable species that would be detrimentally affected by spraying is the essence of the proposed technique. Transline affects some 6 families with at least 79 genera (albeit some with species that are not desirable).

    Please expand a description of the cutting/removal technique. Is it hand clipping at ground level? Is it weed whipping? Is it mowing? How much hand clipping, for example, could a person cover in, say, a 3-hour, volunteer workday. Follow-up in any restoration effort is always critical in order to successfully eradicate a weed species. More info, please.

    At Poplar Creek/Carl R. Hansen Woods there is at least one area (not ever under restoration) where crown vetch covers at least 1 acre.

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  2. Kirk,

    Thanks for the good question. I referred it to Eriko Kojima, who has a lot more experience with this method than I do. She wrote:

    We typically go after crown vetch as soon as we can find it, before bloom if possible, definitely before seed set. If we find it only after it has partly gone to seed, we need to add the step of carefully clipping off and bagging all mature and immature seed pods.

    We clip all the vegetation among and near the crown vetch - all the way to the ground in most cases. It is important to coach volunteers to avoid clipping off some of the crown vetch in the process. The main reason for doing the clipping is to expose the entirety of the crown vetch to see and spray the whole infestation and not inadvertently miss any. We try to spray every leaf and stem of the crown vetch. We then flag and map the area and return a week or two later to check if there are any resprouts or any parts that we missed. We may check again that same year. And we keep the red flag up and check it the following year. It is prudent to check any area that has had crown vetch for three years. It goes without saying that it takes much longer to do the clipping than the actual spraying. We clip and spray, then move on to the next patch. We start with the ones that are infesting the highest quality areas then go to the lesser priority areas.

    Because of the clipping, desirable are not harmed by the herbicide, but the primary benefit is to expose the entirety of the crown vetch. To reiterate, our goal is to completely eliminate the crown vetch.

    Following this painstaking approach motivates us to be serious about this pest. We have become very vigilant about looking for crown vetch and finding it while it is a new, small infestation. As soon as we find a new patch, we run home and run back with the Transline herbicide.

    All our experience is with small patches, less than ten or fifteen feet across.

    Hope this helps,
    Eriko

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  3. The team of restoration practitioners, of which you are included, constitute the greatest combined amount of brain power dedicated to ecological restoration in any given area on the planet. If the team says the outlined procedure has been proven to be effective by monitoring for a few seasons after the treatment, then this must be considered as fact.

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    1. My experiences have not been with personally applying Transline herbicide. I refused to pay the high price required for the small about of crownvetch control work I have time to do.

      The first experience with applying Transline herbicide to crownvetch I would like to bring to everyone’s attention was from the discussion at the 2018 Grassland Restoration Network’s visit to Horlock Hill Prairie in LeRoy Oakes Forest Preserve in Kane County. Horlock Hill Prairie is a prairie reconstruction that received transplants from other locations as these locations were being destroyed. Patrick Chess gave the tour. At one point, we looked at the results of targeted spraying of crownvetch with Transline. The Transline had not prevented crownvetch from returning the next year and the current year’s spraying had highly visible impacts on the many prairie composites (Silphiums most visibly). Patrick Chess said this is an example of “What not to do.”

      The second experience with applying Transline herbicide to crownvetch (and bird’s-foot trefoil) is observations I have made from the work of staff at Spring Valley Nature Center in Schaumburg, Il. The staff told me they spray the crownvetch (and bird’s-foot trefoil) with Transline. They have been spraying crownvetch (and bird’s-foot trefoil) with Transline every year for many years (likely well over a decade). The repeated spraying of crownvetch has not even reduced the size of the patches. The spraying kills the plants back to the ground for the season preventing seed production, so the patches have remained about the same size for several (or more) years.

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    2. Given the above experiences, in my own crownvetch control efforts I have chosen to use non-selective, but very effective, glyphosate herbicide and apply it selectively. I found a product by Greenshoots that dispenses the herbicide as a foam. I tried the methods shown in one video, break a stem and apply the herbicide foam to the broken stem, but I found this to be too slow when tens of thousands, if not hundreds of thousands, of stems needed to be treated regularly. I just started grabbing as many stems as I could in a bundle, squirting foaming herbicide in the middle of the bundle, and then squeezing the bundles of stems up to the tip of the last leaf until the entire plant was covered with herbicide. This proved to be faster and very effective but was using more herbicide than necessary. To minimize off target damage as much as possible, I did trials with reduced concentrations of herbicide (below what was recommended for treatment to bent stems) and determined that the minimum active ingredient of glyphosate that would be effective was between four and five percent.

      I have since applied foaming glyphosate to handfuls of reed canary grass stems, handfuls of purple loosestrife stems, and flowering spurge stems. This concentration works well on reed canary grass if only four to six inches of stem/leaves up from the base are covered. Purple loosestrife needs at least six inches of stems/leaves covered up from the base in Spring and a reduced amount in fall. I just started applying foaming glyphosate to flowering spurge stems this spring and won’t know if my application has worked until next year.
      I have marked adjacent plants (violets, bergamot, culver’s root) that have shown impacts from foaming glyphosate being applied to invasive plants adjacent to (and in the case of violets over) them. If only the minimum concentration and amount of glyphosate foam necessary to control the invasive species is applied and the glyphosate foam is applied as low to the ground as possible then adjacent plants that did not get foaming glyphosate directly on them recover the next year. To reduce impacts on adjacent species further, I am now test what concentration of glyphosate in foam will be effective when applied to four inches of stem length at the base of crownvetch stems. As Bill Kleiman likes to say, “When you are in good areas tighten up your application.”

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    3. The described method would be faster than the method you describe since the vegetation would not need to be clipped. It is still time consuming since each plant must be treated (reed canary grass, purple loosestrife), handfuls of stems must be treated (crownvetch), or each stem of a clone must be treated (flowering spurge). When I apply herbicide in this manner, I try to approach treating 300 reed canary grass or purple loosestrife plants. The limiting factor is squatting down to apply the herbicide low to the ground. This is very tiring to certain leg muscles. However, this method is great in a high-quality area where you want to control invasive species without killing other plants. In areas highly invaded by invasive plants, I can cover two to four hundred square feet in three hours which is the most time I am willing to continuously apply herbicide in this manner.

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    4. Today, I spent a little over an hour applying foaming glyphosate to about four inches of stems at the base of crown vetch in quality prairie. I had to move all the other plants out of the way searching for small crown vetch plants, squirt the herbicide into my gloved hand, squeeze my hand around the stem to cover it with herbicide, then pull any leaves off that had gotten herbicide on them if they were nontarget plants. I only was able to cover about 30 square feet. More than any other invasive plant to control, crown vetch leaves me feeling defeated.

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    5. James, glyphosate doesn't work well on it. Try Milestone (Aminopyralid), it's exceptionally effective against legumes.

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    6. If I completely cover crown vetch with four to five percent active ingredient glyphosate foam, the crown vetch dies. If I am careful and get little to no herbicide on adjacent plants, they show impacts but recover the following year. Still, I am trying to do better.

      Hand wicking herbicide with glyphosate is an approved method. To my knowledge, hand wicking is not approved for Transline or Milestone.

      I just cannot spray herbicide in areas with quality plants. I have seen too many plants I have known for many years kill when adjacent weeds were sprayed. I would only spray herbicide in pure stands of invasive species in spots not within two feet of anything of quality.

      The idea of cutting off all quality plants so the crown vetch receives most of the spray is intriguing. I think the method I have been using works just as well, harms the desirable native species less (helping them keep resisting invasion), and is faster. However, I have not compared the two methods in a study.

      In infested areas, it is very time consuming to locate each crown vetch plant (or group of plants), move other vegetation out of the way, and carefully cover the crown vetch with herbicide. I fear that if I used a method that causes more damage to the native plants, the long-term result might be that the crown vetch infestation would be worse.

      I have seen crown vetch repeatedly rebound from spraying along right-a-ways where a broad-leaf selective herbicide application is used. This regularly sprayed area continues to be dominated by crown vetch, teasel, spiderwort, field thistle, annual weeds, eastern red cedar, stunted buckthorn, Callery pear, and some sparse native grasses. I do not want adjacent quality prairie to turn into this eco-hellscape. Consequently, I am careful to apply herbicide in a manner to minimize damage to existing native plants.

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    7. Where can I buy Transline?

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    8. Here is the video I mentioned above for broken stem treatment of crown vetch. This is the most selective method I have found that would an excellent choice for high-quality areas where you don't want to kill any other plants. As mentioned above, I mostly apply the foaming herbicide using a gloved hand covering the foliage. This method is faster but also causes damage to adjacent non-target plants which so far have all fully recovered.

      https://www.youtube.com/watch?v=jW9Jk56Jr08

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  4. I wrote the following blog post to contrast applying glyphosate foam to crown vetch stems with the recommended method of spraying the crown vetch with herbicide (Transline or Milestone). I hope it gives you an idea of the difference in quality that can result from the much more effort intensive application to each stem or a group of stems.

    https://stewardshipchronicles.blog/2023/08/21/crown-vetch-control/

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  5. Astute readers will notice that I discussed controlling flowering spurge, a valued native, when what I am really working on controlling is leafy spurge, an invasive species. I know the difference. I just sometimes mix up the names of plant species until I've put what I have written aside and look at it later with a clear mind.

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