Yellow and white sweet clover

Posted on July 11, 2024 by Grassland Restoration Network blog

By Bill Kleiman

There are likely a lot of opinions about if and how sweet clover should be controlled, and I encourage you to share your experiences in the comments. What follows has been my experience over 30 years at Nachusa Grasslands.

June 25, 2013: Bill hauling out yellow sweet clover
July 11, 1997 Upland prairie planting full of white sweet clover being mowed

When I first started in 1993 there were two prairie plantings that were several years old and had come up in a lot of white sweet clover. We decided to mow it as low as we could after the Fourth of July. The above photo shows one of these prairie plantings with a very thick cover of white sweet clover. If we had chosen to spray this there would be no prairie planting remaining. So we mowed it.

The rule of thumb is to mow below the lowest leaves of the sweet clover. The clover drops its leaves starting from the leaves closest to the ground. By the Fourth of July the lowest leaves of white sweet clover are several inches above the ground so the mower can cut them below those leaves. The plant is a biennial so by the second year it is quite tall, and if all the leaves are mowed off there is no signal from the plant to re-sprout. Therefore it dies and no seed sets. But don’t wait too long to mow such that seed is on the plant.

Did this work? Very much so. We did occasional patch mowing over the next several years but at this point 30 years later there is just a sprinkling of sweet clover to chase down. Now, some might say it would have gone away on its own, with episodic flushes now and then. Maybe. We left no patches to test this idea.

The mowing must be very close to the ground. An offset hay mower does the best with this because the tires then don’t crush the stems and make it hard to mow the plant. Twice we had an offset hay mower do the task. The other times we had a standard rotary mower with a sharp blade running as low to the ground as possible. We also will use a batwing mower. We have used long hand scythes too for small patches.

We also do a lot of spading of sweet clovers. We haul them out if in seed. And we spot spray them at times if the situation seems to call for that. Most any broadleaf herbicide will work.

Some areas we have are simply ruderal junk, and you might have a flush of sweet clover, essentially no native plants, and the ground is too rough to mow. In such a place we might broadleaf spray across the patch. This quiets the situation for the season, but at some point we will want to establish native habitat and will seed this spot and try to manage it. When to plant a formerly ruderal area is tricky. Is the soil full of invasive weed seed? Do we have the time to care for it if it comes up in invasive weeds? I am not as intimidated of sweet clover as I am of say birdsfoot trefoil or those invasive Lespedezas.

For yellow sweet clover, the timing of the mowing is important. If mowed too early, before late flower, the plant will re-sprout and bloom and we assume set seed as little bonsai yellow sweet clovers.

July 16, 2020 workday to remove mostly yellow sweet clover from a new planting at the Williams tract. A weed scythe is on the ground. The plants in bundles to be hauled off to burn.

Here is Kevin Scheiwiller on sweet clover:

I have a response that reflects my personal opinions that have been formed from working with multiple agencies who may or may not agree with my opinion.

Having a group of dedicated people who care about the ecological health of a site is the most important and effective way to treat sweet clover or any weed really. Continued hand pulling is incredibly labor intensive, but has produced great results in many instances. This can take one or multiple decades just to clear out a moderate sized (50-100ac) restoration. High-quality, smaller restorations are important, but will not achieve our goal of large scale biodiversity conservation.

Some groups choose to ignore sweet clover completely in order to go after other more aggressive, exclusionary weeds. Many land managers have an anecdotal story of mowing sweet clover and reducing it by X%. We know that Transline and Milestone work great on it, but Juli Mason’s most recent post has got me thinking that this approach could be creating more harm than good by leaving high levels of residual herbicide in the soil. 

I’m starting to believe that the best approach is to spot mow the large patches while it is in full bloom and continue to overseed these areas with more prairie forbs. I don’t think this will necessarily get rid of the Sweet Clover but will continue to add competition and make it more palatable to spray or hand pull the stragglers. 

More passionate stewards across more acres is the best solution. 

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Registration Opens for GRN Workshop at Nachusa Grasslands, Franklin Grove, Illinois, September 10 and 11, 2024

Posted on July 3, 2024 by Grassland Restoration Network blog

Our target audience are a mix of staff with various experience levels who are involved in creating high diversity habitat for an agency or non-profit.   We can be a bit wonkish on tools, techniques, and strategies. Attendees might be a seasonal crew member, or a new hire who would benefit from interacting with seasoned experts.  They may be people who do the science of restoration.  The mix of folks who attend these workshops has been enjoyable. 

Agenda: We have several concurrent field trips planned, to keep the group size low enough for discussions to prosper.  We will look at and discuss various prairie restorations, a savanna or two, equipment used, our seed room, on-going science work, brush work and its overlap with prescribed fire.   

Here is a link to the Event Brite invite: https://www.eventbrite.com/e/grassland-restoration-network-workshop-tickets-925954965227

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Managing Invasive Wild Chervil (Anthriscus sylvestris) in Natural Areas

Posted on June 13, 2024 by Grassland Restoration Network blog

By Jason Johnson, Natural Resource Manager with Forest Preserve District of Kane County

Invasive wild chervil

Wild Chervil (Anthriscus sylvestris) is an herbaceous biennial or short-lived perennial introduced to the US from Europe, is about 3 feet tall, and in the Apiaceae family. It has a hollow stem, white umbel flower, and tripinnate leaves. Chervil blooms before most of these other common look-alikes such as Queen Anne’s Lace (Daucus carota), Japanese Hedge Parsley (Torilis japonica), Sweet Cicely (Osmorhiza longistylis, O. claytoni), and Poison Hemlock (Conium maculatum). Chervil spreads rhizomatously as well as producing large quantities of viable seeds. It forms dense stands, displacing native species. Shaded lowlands, especially near creeks, seem to be a favorite habitat for this invasive species. Flowing water and human activities, especially mowing, are the most common means of dispersal. On the plus side, the seed bank is very short lived. Seeds only survive one or two winters.

Chervil was first observed in Kane County, IL in 1975, but was not widely distributed until the late 1990’s or early 2000’s. By 2007 it was exhibiting rapid spread throughout the county; particularly in roadside ditches and has since spread to many of the surrounding counties. By my observations, Kane County has seen the worst of it in northern Illinois for some reason.

Invasive chervil on a right of way

Forest Preserve District of Kane County staff began noticing large populations of Chervil in a few preserves in the mid-2000’s and began treating them. From about 2007-2012, Chervil populations were exploding across the county and they were spreading into more and more County Forest Preserves. Roadsides in some townships were full of it and it was spreading into preserves from those road ditches. Creek corridors in a few preserves also had large infestations with very low native plant diversity. Because the Forest Preserve District holds land in so many disjunct parcels, we have a significant amount of edge. All of those edges are incredibly vulnerable to invasion by weeds. As Chervil spread around the county, we decided that it was necessary to focus a large effort on controlling it as part of our overall mission to preserve and protect the public lands of Kane County. Over the years, our list of Chervil populations has grown, but fortunately the size and density of those populations has been reduced. It is difficult to eradicate weed populations when you have a constant influx of new seeds, but even the densest populations on neighboring property are being held at bay with annual follow-up visits to treat scattered individuals that are trying to reinvade the preserves.

Invasive chervil on a creekside

When the District first began treating Chervil around 2007, we used glyphosate. Glyphosate is effective, but is not ideal due to its non-selectivity. An attempt at mowing it was made, but quickly abandoned due to how highly labor intensive it was. Also, the large root system of the plants allowed them to re-flower rapidly; defeating the efforts of the mowing crew. District staff began looking for an effective broadleaf specific herbicide to use on Chervil. Ben Haberthur, Restoration Ecologist at the time; now Executive Director, ran a field study in 2012 testing several different herbicides and determined 0.5% Transline (Clopyralid) as the best option. We have since increased the concentration to 0.75%, or 1 oz/gal., which provides better results. Rodeo (Glyphosate) was tested at 2.5% and it did the job, but as previously mentioned, is non-selective. Escort (Metsulfuron methyl) and Milestone (Aminopyralid) were also tested but did not have as favorable results. In hindsight, I think that Milestone may in fact work, but it was tested at too high a concentration; which killed all vegetation.

After almost 15 years of consistent field use, 0.75% Transline has shown itself to be very effective at controlling Chervil. Today, District crews begin spraying Chervil populations as early as March. Chervil is one of the first plants to green up in the spring, so is easy to locate early. Once flowers form, crews clip the heads to prevent them from going to seed. Follow-up visits continue into May until seed set. Due to the short-lived seed bank, large infestations are relatively easy to bring under control, however, if there is an off-site seed source the area will need to be monitored annually.

It is possible to treat large, established Chervil populations late in the year. Chervil seems to green back up in the fall and existing populations may be sprayed with glyphosate as late as November or December if the weather is mild. Native species have gone dormant by this time and thus will be protected from the effects of the herbicide. This method does only provide partial control of Chervil, but is helpful in reducing the size of large populations that were not discovered or not able to be treated the preceding spring. The reduced population size makes follow-up treatments easier the next spring.  

Bill Kleiman notes he tried spading chervil and found it difficult, but ok for a few plants.

wild chervil leaves are tri-pinnate. Photo BK
wild chervil flowers. Photo BK
Photo by BK. Wild chervil has this characteristic ridged stems with fringe of hair at leaf nodes. Hairy on the lower stems and smooth on the upper.

Here are a few sites to look at:

https://www.nwcb.wa.gov/weeds/wild-chervil https://www.vtinvasives.org/invasive/wild-chervil https://kingcounty.gov/en/legacy/services/environment/animals-and-plants/noxious-weeds/weed-identification/wild-chervil

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Finesse vs. Brute Force in Invasive Plant Management

Posted on June 6, 2024 by Grassland Restoration Network blog

Part 3 – Stop Spraying Thistles!

By: Julianne Mason, Restoration Program Coordinator, Forest Preserve District of Will County

Here are my top reasons for not spraying thistles.  I’m specifically talking about Canada thistles (Cirsium arvense), but who knows, maybe this applies to other non-native thistles too.

1.  It’s Unnecessary.  When native forbs get established, Canada thistles fade away.  Read about my experiences at Prairie Bluff below for an example.  Note that Canada thistles seem to coexist happily and indefinitely with non-native, cool-season grasses.  The fading phenomenon seemingly happens when native forbs get established and displace them.

2.  It’s Counterproductive.  Spraying thistles causes collateral damage to nearby forbs and can inhibit re-establishment of desirable forbs due to residual herbicide activity in the soil [See Part 2 of post] when herbicides like Transline or Milestone are used in excess.  This results in less competition for the thistles and perpetuates their re-establishment.

3.  Don’t We All Have Other Invasives to Combat?  There are more invasives displacing native species than we collectively have resources to address.  We should be focusing our efforts and herbicide on the ones that are displacing natives and reducing biodiversity (e.g., Phragmites, reed canary grass, etc., etc., etc.).  Yes, thistles are long ingrained in our culture as noxious weeds because they are problems in ag fields and pastures.  But, that doesn’t necessarily mean that they are serious problems in natural areas.

  1. Let’s Distinguish Between Weeds that are Symptoms of Problems vs. Causing Problems.  Thistles are usually symptoms of one of two problems.  One is when not enough native forbs are present.  This often happens in early restorations, when native communities are first planted in former row crop fields.  Or, it can happen when previous herbicide applications cause dead zones or “holes” in the native cover.  The second problem when thistles persist is the dominance of non-native, cool-season grasses.  Thistles seem to happily coexist indefinitely with non-native, cool-season grasses.  In this case, burning, overseeding natives, and addressing the C3 grass problem (we use post-burn application of clethodim herbicide) are the prescription, not spraying thistles.  Once the C3 grasses are dealt with and the seeded natives can get established, the thistles fade.
  2. Combat Thistles with Seed, Not Herbicide.  If thistles are symptoms of a lack of native cover, then combat the issue by a dormant seeding of native species, especially native forbs.

Case Study: Prairie Bluff – The Tale of Two Restorations

Here is my perspective-changing experience on thistles from the prairie restorations at Prairie Bluff Preserve in Lockport, Illinois.

Prairie Bluff is a 600-acre former row crop farm.  When it was in agricultural leases (prior to 2019), we restricted the use of chemicals that have groundwater advisories, which includes most broadleaf herbicides.  As a result, the ag fields became very weedy and Canada thistles were persistent throughout the fields; they were chronically just being suppressed by row cropping.  Funding for restoration of the preserve came from two different primary sources.  The two different restoration projects, although happening simultaneously, took almost opposite approaches regarding thistle management.  

Western Project Approach: Do a good dormant seeding and don’t worry about the thistles.

  • Dormant seeded with full prairie and wetland mixes – Feb 2020
  • Mowed or spot mowed the weedy parts of the prairie- Summer 2020 & 2021 (I don’t know if this was helpful or necessary, but it made both them and the grant agency feel like they were doing something to help the prairie establish.)
  • Prescribed burn – March 2022

Eastern Project Approach: Seed a more limited native matrix and battle the thistles into submission before establishing a more diverse prairie.

  • Boom sprayed Milestone herbicide – Fall 2019
  • Seeded native grasses, graminoids, and limited forbs – Feb 2020
  • Spot sprayed widespread thistles (essentially broadcast sprayed) with Milestone herbicide – Summer 2021
  • Prescribed burn – April 2022
  • [Summer 2022 – I realized that the western restoration was looking immensely better and decided to change course on the thistle approach in this restoration.]
  • Summer 2022 – laid off herbicide and avoided spraying thistles
  • Tested herbicide residual in soil – August 2022 [see Part 2 of blog post]
  • Overseeded more diverse mixes – February 2023

Western Area Results – Thistles Ignored, Thistles Faded:  In the western project area, where the approach was to not herbicide the thistles, there are almost no thistles remaining in the restoration.  It is a good-looking early restoration, dominated by Canada wild rye (Elymus canadensis), yellow coneflower (Ratibida pinnata), wild bergamot (Monarda fistulosa),golden Alexanders (Zizia aurea), foxglove beardstongue (Penstemon digitalis), rattlesnake master (Eryngium yuccifolium), field oval sedge (Carex molesta),and many other natives.  The diversity of the prairie establishing reflects the original seed mix. 

The only Canada thistles remaining in the western project area are present along the trail corridor.  There, non-native, cool-season grasses that were planted to be mowed turf along the trail shoulders have expanded out into the prairie.  The thistles are persisting in the non-native C3 grass zones, but not anywhere where natives have established.

Eastern Area Results – Thistles Battled with Herbicide, Prairie Restoration Suffers.  In the eastern project area, there are still lots of thistles in the restoration.  Lots of thistles.  The seeded native grasses are becoming established, but besides that, the rest of the vegetation is weeds.  Now the restoration has been overseeded with properly diverse mixes and we are avoiding widespread herbicide use to allow the seeding to establish.  Hopefully, the recently seeded native forbs will be able to establish well and displace the Canada thistles and other weeds (sow thistles, annual/biennial weeds, etc).  I’ll keep you posted on how the restorations are progressing in a few years. 

Just for good measure, here’s one more photo comparison of the western project area at Prairie Bluff where the thistles were not treated with herbicide, compared with the eastern project area where the thistles were originally boom sprayed with herbicide.  It’s only anecdotal data, but I think it’s time to stop spraying thistles.  Restorations are a lot easier and more successful when you view thistles as symptoms of a problem (i.e, lack of native cover) and not the problem themselves.

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Finesse vs. Brute Force in Invasive Plant Management

Posted on May 30, 2024 by Grassland Restoration Network blog

Part 2 – Soil Residual Effects of Herbicides

By: Julianne Mason, Restoration Program Coordinator, Forest Preserve District of Will County

To preserve or restore native plant diversity and community integrity, it’s often necessary to apply herbicides to kill invasive plants.  However, using herbicides can cause collateral damage to the native plant species that we’re trying to protect.  In addition to direct collateral damage, I have begun to appreciate how the soil residual effect of herbicides can inhibit establishment of the native species that we’re trying to restore. 

We spend a lot of money and crew-hours purchasing or collecting seeds of native plants to restore native plant diversity.  However, I have seen many examples of where we have gotten almost no native plant establishment from these seedings.  I started to consider the mechanism of how herbicide use to control invasive plants may be implicated in the lack of success of the seedings. 

In a recent mesic prairie restoration project in northeastern Illinois, the PBP project area had been sprayed with Milestone herbicide (aminopyralid) to target Canada thistles (Cirsium arvense).  Before I spent a hundred thousand dollars on native seed, I wanted to make sure that the residual herbicide level in the soil was low enough to allow the native seed to establish. 

In another prairie restoration area in northeastern Illinois, we boom sprayed the MRP project area twice with Transline herbicide (clopyralid) to target teasel (Dipsacus laciniatus) and birdsfoot trefoil (Lotus corniculatus) before seeding a mesic prairie mix.  I wanted to know why the seeding didn’t establish, and whether the residual herbicide level in the soil was low enough to try overseeding natives again.

For both areas, I sent soil samples to the South Dakota Agricultural Laboratories for analysis during late August 2022.  At the same time, I put soil samples from the two project areas in plug pots and seeded them with black-eyed Susan (Rudbeckia hirta; left plugs), wild bergamot (Monarda fistulosa; right plugs), and cilantro (front two plugs).  Black-eyed Susan is susceptible to both herbicides, wild bergamot is relatively tolerant of both herbicides, and cilantro is an annual that germinates readily (and I had extra seed lying around).  In the fall of 2022, most seed had germinated of all species, and there was not any difference between the soil samples.

By the spring of 2023, there was a notable difference between seedling survivorship in the soil samples with higher levels of residual herbicide and those without detectable herbicides.  In MRP-3, which had the highest level of clopyralid (from Transline herbicide) in the soil at 6 ppb, both the black-eyed Susan and wild bergamot seedlings were dying.  In PBP-6, which had the highest level of aminopyralid (from Milestone herbicide) in the soil at 6 ppb, the black-eyed Susan seedlings were dead, but the wild bergamot seedlings were still alive.  In nearly all the soil samples where the herbicide levels in the soil were below the laboratory’s detection limit, both black-eyed Susan and wild bergamot seedlings were alive.

Take-Home Messages:

  1. If you suspect that you might have too much herbicide residual in the soil, get it tested before spending a lot of time or money seeding natives!
  2. Be mindful of uncalibrated spraying – both uncalibrated boom spraying, broadcast spraying with a gun, and backpack spot spraying.  Our two examples with the highest soil herbicide levels had received an uncalibrated spray (via backpack spot spray or uncalibrated boom).
  3. Be mindful of the accumulation based on consecutive years of spraying.  Our two examples with the highest soil herbicide levels had also been sprayed two years in a row.

Here is a summary of the management history, the soil herbicide level, and the germination study results.

MRP-1:  No recent herbicide activity.

Clopyralid level in soil: below detection limit.

Germination results: Establishment & survival of black-eyed Susans and wild bergamot.

MRP-2: Broadcast sprayed with Transline herbicide (0.5%; ave 12 fl oz/ac) 1 year before soil tests.

                Clopyralid level in soil: 3 ppb

                Germination result: Establishment & survival of black-eyed Susans and wild bergamot.

MRP-3: Broadcast sprayed with Transline herbicide (0.5%; 19 fl oz/ac) 2 years before soil tests.

Broadcast sprayed (uncalibrated) with Transline herbicide (0.5%; 40 fl oz/ac) 1 year before soil tests.  *Note: this application exceeded the annual maximum application rate (24 fl oz/ac).

 Clopyralid level in soil: 6 ppb

Germination result:  Both black-eyed Susans and wild bergamot germinated but died the following spring.

PBP-1:  No recent herbicide activity.

                Aminopyralid level in soil: below detection limit.

                Germination result: Establishment & survival of black-eyed Susans and wild bergamot.

PBP-2: Broadcast sprayed with Milestone herbicide (0.25%; ave 2.6 fl oz/ac) 1 year before soil tests.

                Aminopyralid level in soil: below detection limit.

                Germination result: Establishment & survival of black-eyed Susans and wild bergamot.

PBP-6: Broadcast sprayed with Milestone herbicide (0.25%; ave 2.6 fl oz/ac) 1 year before soil tests.

                Then, spot sprayed teasel with Milestone herbicide (0.25%) 2 months before soil tests.

                Aminopyralid level in soil: 6 ppb

Germination result: Black-eyed Susans germinated but died (only annual foxtail grass visible in 2023 photo).  Wild bergamot established.

Conclusion:  Remember, it’s not only Kill, Kill, Kill.  In conjunction with killing invasive plant species, it’s equally as important to seed and promote establishment of a diverse native community.  To allow native seed to establish, good practices are to avoid excessive spraying, be mindful of the soil residual effects of herbicides, and get the soil tested as necessary to know when it’s safe to apply the precious native seed.  A finesse approach is much more effective than brute force in invasive plant management!

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Finesse vs. Brute Force in Invasive Plant Management

Posted on May 23, 2024 by Grassland Restoration Network blog

Part 1 – The Soapbox

By: Julianne Mason, Restoration Program Coordinator, Forest Preserve District of Will County

Invasive plant management often feels like a brute force exercise.  We use the language of battle when we talk about killing invasive species.  However, it’s important to keep in mind that the actual goal isn’t to kill invasive plants – it’s to preserve or restore native plant diversity and community integrity.  It’s not only Kill, Kill, Kill.  Yes, we need to control invasive plant species before they take over and reduce the diversity of natives.  Yes, it’s often necessary to apply herbicides to kill invasive plants.  But it’s equally as important to do so in a way that promotes or re-establishes a diverse native community.  Otherwise, we’re caught in a downward spiral of killing plants, resulting in bare holes that get colonized by more weeds and invasive plants, killing those plants, creating more bare holes that get colonized by weeds, etc., etc., etc. 

The finesse strategy of invasive plant management recognizes that it’s generally most effective to use a selective chemical, selective application method, or selective timing to be able to control the invasive while minimizing collateral damage to native plant species.  Despite being as selective as possible, using herbicides can cause collateral damage to the native plant species that we’re trying to protect.  Furthermore, causing collateral damage to native plants can reduce the competition faced by invasive plants and can tip the localized playing field to favor more invasives.   I’m not saying that we shouldn’t control invasive species – we absolutely must do so to preserve native plant diversity.  However, we need to be mindful that using herbicides effectively must both: 1) effectively control the invasive, and 2) minimize impacts to native plants, or at least not inhibit their re-establishment. 

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Nachusa Grasslands Prescribed Fire Report

Posted on May 16, 2024 by Grassland Restoration Network blog

By Bill Kleiman

Lessons learned:

  • Fire breaks make or break you.
  • Daily attention to details makes a fire day go.
  • Volunteers, staff, and guest agencies can work seamlessly.
  • Most years there are under two dozen burn weather days so make use of them.
  • Mentor others
Four of the crew are from the Forest Preserve District of Cook County.  They sometimes send their fire crew to help others burn.  It is a win for them and us. When you burn with other crews you learn and confirm.  Two crew are from the Friends of the Illinois Nature Preserves.  There is one TNC seasonal there and four Nachusa volunteers. Getting the job done.
Big Woods unit burning well.  The flame lengths are modest but these fires set back the brush and support the ground layer plants, and the fires sustain the oak and the hickory which do well with sunshine.

The bottom line:

  • Number of burn days was 19.
  • We burned 2,204-acres of Nachusa, close to a record high, on 16 burn units
  • We assisted on 874-acres on 12 units.
  • Average size of a burn unit was 138-acres with a unit as small as 3-acres and big as 300-acres.
  • Average crew size was 14.
The Northern Illinois University Fire Huskies were on the fire line.  Here is NIU student Allyson Thompson with her mentor for the day, Susan Kleiman.  We are literally passing the torch to the next generation. Ok a flapper in this case.
Kaleb Baker (INPC), Pete Oliver (citizen), Phil Nagorny (TNC) at the Hill Site owned by the Middle Rock Conservation Partners.  At the base of the hill you can see where Kaleb walked a circuitous path with that red torch.
A day after the Hill Site fire with shrubs top killed by the heat but an old bur oak stands sentinel, that tree perhaps is old enough to have had Native American fires run past.
This is a new knife mulcher made by Denis Cimaf on our also new Cat skid loader.  This mulcher uses a sharp knife edge to make easier work of brush.  This allows this 100 hp machine to do more work than the older blunt toothed style brush mower.   The downside is you need to sharpen the teeth every day, or every other day, which takes about 20 minutes. 
 

For the complete report with more photos, map, data, and a list of fire crew go here: https://www.nachusagrasslands.org/controlled-burns.html

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Basal Bark Herbicide Treatments for Invasive Shrubs – the Type of Oil Carrier Matters!

Posted on May 1, 2024 by jmasonfpdwc

By: Julianne Mason, Ecological Management Supervisor, Forest Preserve District of Will County, IL

If you haven’t read Kaleb Baker’s recent post about his study that showed the effectiveness of basal bark treating amur honeysuckle, an invasive shrub, please do so now.  In the comment section of the post, one person noted that their previous basal bark herbicide treatments had been ineffective that had used diesel fuel as the oil carrier. The commenter wondered if the type of oil carrier used in the basal bark application may make a difference.  I came across my own case study recently suggesting that the type of oil carrier may make a huge difference in effectiveness of basal bark treatments.

As background, my agency (Forest Preserve District of Will County, Illinois) has been using basal bark treatments extensively to combat invasive shrubs for the past 8 years or so.  Our crew, contactors, and volunteers have done basal bark treatments to invasive shrubs covering over 10,000 acres during that time.  Our most common invasive shrubs have been bush honeysuckle (Lonicera tatarica, L. maackii, L. x bella), common buckthorn (Rhamnus cathartica), glossy buckthorn (Frangula alnus), multiflora rose (Rosa multiflora), and autumn olive (Elaeagnus umbellifera), but we target around 25 different species of invasive shrubs.   We typically use 15-20% triclopyr ester (e.g., Garlon 4) herbicide in bark oil. My general assessment of our treatments is that Kaleb’s reported effectiveness of >95% mortality of honeysuckles from basal bark treatments has been true for us across all invasive shrub species.  It has been consistently excellent, especially for non-rhizomatous species.  However, the shrub must receive a 360-degree application for almost all species, except multiflora rose and Japanese barberry.  For those two thorny invasives, all the canes must be sprayed at the base, but (thankfully) a 360-degree application is not necessary.

Proper 360-degree basal bark application (left) – this shrub will die. Missed individuals and ones only partly treated (right) with a basal bark application will not die.

Our basal bark herbicide treatments to invasive shrubs have been consistently effective, but it often takes a long time (12-18 months) for bigger shrubs to look fully dead.

Of note, it often takes bigger shrubs a long time to die from a basal bark treatment, especially big honeysuckles, autumn olive, and buckthorns.  They often leaf out and look perfectly happy the spring following a treatment, only to slowly succumb to death one year or so after treatment.  I generally find that by 12-18 months or so after treatment, most everything will have died if it had been properly treated.  Also of note, like Kaleb’s study, we generally use backpack sprayers to do the application.  I have not compared the effectiveness of basal bark applications done using paint rollers or brushes.

This past week, I came across a notable exception to our consistently effective basal bark treatments.  There are two hedgerows at a preserve near Braidwood, Illinois that were basal bark treated during the fall of 2022.  The treatment had been done thoroughly and well (i.e., proper 360 degrees).  The hedgerows were primarily composed of large honeysuckles, although there was a smattering of multiflora rose, autumn olive and other invasive shrub species too.  The honeysuckles and other invasive shrubs leafed out during the spring of 2023, which was not surprising or unusual following a fall basal bark treatment.  However, it was surprising to me that all of the basal-bark treated shrubs are still alive now, 18 months after treatment.  The treatment was completely ineffective. 

Unusually ineffective Fall 2022 basal bark application, viewed 18 months after treatment.

When I inquired into the unusually ineffective treatments in more detail, I found out that methylated seed oil (brand: Dyne-amic) had been used as the oil carrier for the basal bark treatments, not one of our usual bark oils.  This makes me think that we should be reporting and considering the type of oil used in basal bark treatments, especially given the seemingly inconsistent and differing results among different people and organizations.  To answer the commenter’s question more precisely, I have never used diesel or kerosene as the oil carrier for basal bark treatments.  However, my experience from the ineffective basal bark treatment of large honeysuckles when methylated seed oil was used as a carrier suggests that the type of oil carrier may have a huge impact on its effectiveness.

This list is not exhaustive, but it contains the brand names of bark oil that our crew and contractors have been using with reliably effective results. 

Not Exhaustive List of Bark Oils

  • Bark Oil Blue LT
    • Bark Oil Red LT
  • Impel Red Oil
  • JLB Oil Plus Improved
  • Premier Blue bark oil

Also, if the cost of bark oil is an issue or barrier, here’s a link to my previous post about cutting the oil with water for basal bark applications.  Using an oil-water emulsion for the basal bark herbicide application has been nearly as effective for us as using straight bark oil as the carrier.  And, it uses less than a quarter of the amount of oil. Some caveats: since it is water-based, it can’t be used below freezing temps. Also, we have observed that the application may not be as rain-fast as quickly. But, it definitely uses less oil product and therefore the materials are less costly when using oil-water emulsions for the basal bark treatments. My recommendation: ditch the methylated seed oil and other weird oil carriers. Use a proper bark oil, do a proper 360-degree application, and enjoy highly effective basal bark herbicide treatments to invasive shrubs.

Posted in Invasive species | Tagged , , , , , , | 8 Comments

A Study on Controlling Bush Honeysuckle

Posted on April 25, 2024 by Grassland Restoration Network blog

By Kaleb Baker

Photo 1. One of the many signs delineating the honeysuckle subplots

Amur honeysuckle (Lonicera maackii) is an invasive shrub that flourishes along forest edges and in open woodlands. Amur honeysuckle shades out native flora with its early leaf-out and prolonged leaf retention, and when left uncontrolled, can produce a near monoculture, threatening biodiversity.

Land stewards everywhere have implemented a variety of different eradication methods, including hand pulling, cut-and-treat with herbicide, foliar-applied herbicide from backpacks or helicopters, basal bark herbicide treatments, and prescribed fire. Continuous treatments and monitoring are needed to eradicate Amur honeysuckle, making the cost, effort, time specificity (amount of nontarget damage), and applicability (when and where a method can work) important factors to consider.

This study explored how effective basal bark treatments and prescribed fire are at controlling honeysuckle, the amount of nontarget damage from those treatments, and the subsequent vegetative recovery. Basal bark and fire are commonly used control methods. The basal bark herbicide was made with 2.5 gallons of Garlon 4 Ultra mixed into 12.5 gallons of basal oil making 15 gallons of 16.67% Garlon 4 Ultra, equivalent to 10% triclopyr ester because Garlon 4 Ultra is 60.45% triclopyr. Basal bark treatments involved spraying the 10% solution of triclopyr around each plant’s base from a backpack, which was both quick and easy. The nozzle was pointed mostly downward (not horizontally), spraying with moderate pressure using a narrow cone pattern.

Figure 1. Depiction of spraying the bottom 15-30 cm (6-12 in) of a bush honeysuckle from 2 directions so the herbicide fully covers the surface all stems to the point of nearly running off. Application sometimes required 3 directions or spraying the inside of a ring of stems to ensure complete coverage.

In this study we included 800 individually marked Amur honeysuckle (Lonicera maackii) at 5 different sites within Nachusa Grasslands and Franklin Creek State Natural Area (Ogle and Lee counties in northwest Illinois). In order to see if the season of application affected honeysuckle mortality or the extent of damage to non-target flora, five basal bark treatments were applied in fall 2017 (11/26 – 12/17), winter 2018 (1/28), early spring 2018 (3/10-3/11), late spring 2018 (5/4-5/5), and a control with no application. (Application caveat: there was no snow during any application). Prescribed fire was administered to half of each of the 5 sites in spring 2018. Honeysuckle mortality was checked in the early fall of 2018 to allow the honeysuckle time to fully die.

All basal bark applications were equally effective at killing Amur honeysuckle (statistically indifferent), regardless of treatment timing. There was an insignificant variation in how effective the treatments were with the late spring treatment only being 96.7% effective. The combined mortality rate of herbicide treatments was 98.4% across all four herbicide treatment seasons, compared to a 2.5% mortality with no basal bark treatment. Mortality was not dependent upon honeysuckle size (height: <1m to 3+m tall, number of stems: 1-12+ stems, or root collar size: 10-150+mm). Prescribed fire did not impact mortality positively or negatively.

Figure 2. Graph shows the bush honeysuckle mortality when checked the fall after treatment with no difference between treatment timings (98.4% averaged across treatment seasons).
 

However, if the plants had been checked earlier in the year, we would have concluded basal bark treatments were ineffective. A subset of individuals across treatments was opportunistically checked on 5/13/2018 to see if they were leafing out. Of the 317 honeysuckle checked, 75% of the treated honeysuckle showed signs of leaf out.

ControlFallWinterEarly SpringLate SpringGrand Total
Leafing Out6443464754254
No Leaf Out02116161063
Grand Total6464626364317
% Leafing Out100%67%74%75%84%80%
Figure 3. Table shows the number of individual honeysuckle found to be leafing out or not on 5/13/2018, just over one week after applying the Late Spring treatment.
Photo 2. A treated honeysuckle (right) that leafed out then died. The honeysuckle on the left was not been treated and is healthy.
 

A 1m2 quadrat was placed around 200 Amur honeysuckle to measure nontarget damage to the plant community in spring 2018. The “ring-of-death” equated to about a 10-inch radius on average. The size of the nontarget damage did not differ based on fire treatment, basal bark treatment season, or any measured size of honeysuckle.


Photo 3. The amount of nontarget damage (aka “ring-of-death”) on year one (2018)
Photo 4. Looking down at one of 200 1m2 quadrats used to measure nontarget impacts of basal bark and fire treatments.



Figure 4. Shown is a chart series of percent living vegetation coverage (native and non-native species) (y-axis) of 80 quadrats with the control treatment on the left in dark blue and the herbicide treatments following in chronological order. Within each chart, the x-axis is the year 2018-2021. Each dot represents the total percent cover of each quadrat, the triangle is the mean percent cover of that treatment that year, and the dotted line shows a linear trendline.

The tendency to revegetate is further exemplified when looking exclusively at native species as shown in Figure 5, meaning the treated areas aren’t being recolonized just by nonnative species.

Figure 5. Shown is a chart series of percent living native vegetation coverage (y-axis) of 80 quadrats with the control treatment on the left in dark blue and the herbicide treatments following in chronological order. Within each chart, the x-axis is the year 2018-2021. Each dot represents the total percent cover of each quadrat, the triangle is the mean percent cover of that treatment that year, and the dotted line shows a linear trendline

However, the communities were simplified in the area surrounding treated honeysuckle. The species richness was impacted by the herbicide treatments. Averaging across all four years, the early spring treatment had 1.4 fewer species than the control and the other herbicide treatments had 1.9-2.3 fewer species than the untreated honeysuckle (Figure 6). Though, there did not appear to be any species or group of species that were particularly susceptible.


Figure 6. Each box shows the richness of native (red) and non-native (blue) species from different herbicide treatments from 2018-2021 from 80 quadrats. The bold center bars are the median. The hinges are the middle 50% of the data, and the whiskers include data from the 1st to 3rd quartiles.

Note (mostly speculative): Some managers prefer using a paint roller instead of a backpack sprayer to minimize nontarget damage. This could limit nontarget damage but could also limit target species mortality because less herbicide is applied to the target. Other managers speculate that rainfall soon after application may increase nontarget damage preferring to not basal bark unless there will be 48 before precipitation.

Key take-aways:

  • Basal bark treatments were highly effective at killing bush honeysuckle (98.4%).
  • While prescribed fire was not effective at killing bush honeysuckle, it did not inhibit the basal bark treatments so fire should continue to be implemented to maintain fire-adapted communities.
  • Basal bark treatments did impact the local vegetative communities (~10 inch radius on average).
  • The “ring-of-death” recovers in time but is slightly simplified.
  • There was some evidence that early spring basal bark treatments had slightly less nontarget damage (~0.5 higher species richness).

For managers, basal bark treatments are another tool in the toolbox with advantages and disadvantages. Below is my current mental framework for some common treatment options and considerations.

ConsiderationsCut-and-treatBasal BarkFoliarForestry Mow
Tool CostLowHighMediumHigh
EffortHighMediumLowLow
Time per AreaHighLow/Medium (stem density dependent)LowLow
SpecificityHighMediumLowLow
TimingNearly anytimeNot summerNot dormant seasonAvoid growing season
ApplicabilityCan be used most placesShould not be used in wet or super sensitive areasShould not be used in sensitive areasShould not be used in wet or sensitive areas

A peer reviewed paper detailing this study has just been published. It can be read for free on open access at this link https://url.us.m.mimecastprotect.com/s/8HJJCADXrnszWR7lsGqmsc?domain=doi.org

Below is a similar post as Kaleb’s. On the Blogsite you can search for related posts, and you can get our weekly posting sent conveniently to your email.

A family affair: Successful control of invasive honeysuckle with basal bark herbicide
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GRN Workshop at Nachusa Grasslands September 10 &11, 2024

Posted on April 18, 2024 by Grassland Restoration Network blog

By Bill Kleiman

Registration will open in June.

Here is a quick update. We would start the workshop mid-morning September 10 and end mid-afternoon on the 11th. We have limited space so we may not be able to accept all who wish to attend. If you can’t make this workshop, we do plan to re-start our annual one-day open house for resource managers in 2025.

These are the themes of tour discussions we hope to cover. We will limit tour sizes to keep the discussion easy and repeat the tours so you can hear what you like.

  • Prairie plantings. We have many very good plantings and some poor ones. Hike through several and discuss lessons learned.
  • Brush work and fire. We will look at habitats where we have used frequent fire in combination with brush mowing and basal bark herbicide.
  • Hand harvesting seed. We will cover how we map and track our seed harvests. How we dry, store, mill, mix and plant seeds. We will also discuss seed harvesting for savanna and woodland.
  • Science. We have a robust science program that we will explain as we look at projects in the field.
  • Fire break preparation and operations: We will look at fire break equipment and pumper units in use. We will look at several fire breaks and burn units to discuss what we have learned to help us get a lot of fire on the ground.
  • Bison grazing program. What results are we seeing after ten years?
  • Volunteer Stewardship and Citizen Science. Tours will have some of our great volunteers as co-leaders and you can hear their viewpoints.
photo by Chares Larry

Since we are starting weed season here are a few posts from the past to consider:

Hand held herbicide sprayer
25 Drums, 1 Applicator, 1 Sprayer & 1 Winter
Invasive Reed canary grass control
Basal bark G4 on Echinacea purpurea
THE 1-2 PUNCH
Weed management tips
Wild Parsnip. Is it invasive or just a weed?
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