Invasive Control - Crown Vetch

I made an effort this year to seek out and spray colonies of the invasive Crown Vetch.  For several years now, I’ve been finding random clumps of this invasive plant scattered about Blue Jay Barrens. 

My efforts began last autumn when I mowed several Crown Vetch infested spots in the field. I returned to those spots in April to spray the early season growth.  I also targeted early season growth between the township road and my field fence.

I elected to use the chemical Clopyralid as a control agent.  Clopyralid is a selective herbicide that targets broadleaf plants, especially legumes.  Unlike glyphosate, which kills all green growing plants, Clopyralid leaves grasses unhurt, so the treated area does not become a big bare spot awaiting the arrival of new invasive seeds.

Within a week, the Crown Vetch was showing the effects of the herbicide.

A month after that, all traces of the invasive plant were gone.

The light colored area in the background at the upper left of the photo is the township road that runs along two sides of a large prairie opening.  A scattering of Crown Vetch plants, remnants of a government funded planting in the early 1980’s, persisted along the shady lane and produced seed that moved with the rain water to establish new plants along the edge of my field.  Hopefully, that influx of seed will now end.

In late May, I found a large infestation of Crown Vetch in a low area that receives runoff water from the road ditches. 

The vetch was growing at a rate slightly slower than its companion prairie forbs, making it difficult to see from a distance.  Fortunately, I was in the area doing some other work and just blundered into the middle of the Crown Vetch patch.  The Clopyralid successfully eliminated the vetch from this site, but it also took most of the other broadleaf plants.  That was a bit of a disappointment, but there was plenty of grass left, so the site was not bare. 

By late June, the Crown Vetch was blooming.  Blooming plants are easy to find and I made sure to search in all places likely to have an infestation.

Crown Vetch is aggressive enough to eliminate all neighboring plants.  By using a herbicide that doesn’t result in the elimination of all species, I have left things in better condition than they would have been if left to the mercy of the vetch.  Crown Vetch increases its growing area by using a technique known as sprawling.  Stalks grow upright by using neighboring plants for support.  Eventually, the stalk overtops the other plants and falls over.  The fallen stalks form a canopy over surrounding plants, causing those plants to suffer from shading and become less vigorous.  The affected vegetation eventually dies and the vetch claims this new growing area.  A single patch of Crown Vetch can eventually cover an entire field.

Most of the Crown Vetch clumps covered less than 50 square feet.  Only one was over 100 square feet.  I’ll have to wait until next growing season to what grows back on the treated sites, but I think the use of Clopyralid has had a positive impact on control of the Blue Jay Barrens Crown Vetch invasion.

Prairie Corridor Project

The final phase of a project intended to create an open corridor between two prairie areas has now been completed.  What was once a vicious tangle of invasive Autumn Olive and Multiflora Rose, now looks almost park-like.  A finish mower and a couple of picnic tables would make this a wonderful place to relax, but I have a different goal in mind.  My hopes are that this area will convert to prairie vegetation and act as a pathway to allow organisms to move freely between an existing prairie area to the upper right and a second to the upper left.  The only task left is to get rid of the few large trees.

I’ve chosen to kill the trees in place by girdling and applying herbicide.  Girdling is the act of removing a strip of living bark around the base of a tree.  This essentially stops the transfer of energy from the leaves to the roots.  Girdling alone will typically kill the top of the tree, but a forest of sprouts will emerge below the point of the cut and the tree will grow on.  To ensure the death of the entire tree, I have applied a 41% solution of glyphosate to the exposed inner bark at the lower part of the wound.  There should be no regrowth here.

The Allegheny Mound Ants that had been foraging up the tree were slightly befuddled by the loss of their path to the ground.  On some trees it took 15 minutes or more before they finally crossed the gap and went on their way.  These ants can be found on every tree in the more open areas of Blue Jay Barrens, but they do not go into the closed canopy woods.

Girdled trees included some growing in the Winged Sumac thicket.  Eventually, shade from the trees would have caused the death of the sumacs.

The dead trees should be a wonderful place for beetle larvae and woodpeckers.  Several of the trees are large enough to accommodate nesting woodpeckers.  Red-headed Woodpecker numbers have been increasing in the area over the past few years and I’m hoping that dead trees in a rather open setting might entice a pair to nest here.

Flowering Dogwood, Dwarf Sumac and a few oaks were left alive.  There are not enough of them to impede the growth of prairie vegetation.  Presence of these three species is consistent with the type of prairie typically found in this area and having them here is in keeping with the management goals of the adjoining fields.

The leafless dead trees will not block enough sunlight to slow expansion of prairie into the area.  In a few years, small limbs will begin to fall from the dead trees.  Larger limbs will follow and eventually, the trunks will come down.  Everything should be on the ground within ten years.  What happens to the fallen material will depend on how and where it falls.  Some will be left on the ground to decompose and some will be moved to facilitate future maintenance of the area.

This area to the west, just outside the trees, will be the primary source of seed for colonizing prairie plants.  Our prevailing wind is from the west and it’s that wind that carries seeds into new territories.  By the time the last tree falls, this area should be healthy prairie.

Fescue Control Trial

There are over a dozen invasive plant species that are on the priority list for control at Blue Jay Barrens.  For some, I’ve found effective control techniques and those species are slowly being removed from the landscape.  For others, I’m still trying to discover effective control techniques.  One group that I am currently working on is made up of introduced cool season grasses commonly used for pasture, hay or landscape purposes.  The most visible members of that group are Tall Fescue, Orchard Grass, Timothy and Kentucky Bluegrass.  They all begin growth early in the season, slow down or enter dormancy during the heat of summer and revive to grow into late fall.  They are most easily detected in late spring when they overtop slower growing vegetation and send up their flower stalks.

Varieties of all of these grasses have been developed to be super vigorous and highly competitive.  Many native plants cannot survive the competition and disappear.  The challenge is to find a way to remove the invasive grasses from the stand without harming the natives.  I have some ideas and decided to try one out on the grass along the trails.  This is what a typical untreated trail edge looks like.  A secondary reason for conducting my trials along the trail edges was the fact that the mature fescue seed stalks lean out into the trail at the precise time that chigger activity peaks.  Brushing the stalks while walking invariably results in chigger bites, so no grass also means fewer chigger bites.

This point, formed by a fork in the trails, was last year thick with Tall Fescue.  Tall Fescue is the most aggressive of the four grasses mentioned.  Having been used for years for pasture, hay and erosion control, Tall Fescue is present on probably every farm in southern Ohio.  Kentucky 31 Tall Fescue was considered the farmer’s friend and because of its ability to survive on the poorest of soils, is probably responsible for much of the farmland soil remaining on the hillsides.  It’s a tough grass, but it has been eliminated from this small spot and the natives remain.

Last December 2, I used the brush mower to trim down dead stalks along the trail and expose the still green fescue beneath. I then applied a 2% solution of glyphosate to the cut grass.  Since most of the native species were dormant with top growth dead, there was no danger of their being damaged by the herbicide.

The effect of the herbicide is clear to see.  In the treated area the non-native grasses have been eliminated.  The untreated area farther from the trail still has a thick stand of grass.

In a very few areas, the treatment was not successful.  Even though the forecast was for dry conditions throughout the day of treatment, a rain shower hit the area about three hours after the herbicide application.  The spray should have had time to dry and adhere to the grass leaves, but since it was cool and I had just mowed off a large part of the leaf, it’s possible that the chemical was diluted enough to render it ineffective.  It could also be that a clump of cut vegetation covered this patch of grass and intercepted the spray or, even though highly unlikely, the guy wielding the backpack sprayer may have just missed this spot.

I noticed just one native species that did not survive the herbicide treatment.  Golden Ragwort, notorious for maintaining green leaves through the winter, went the way of the exotic grasses.  In this case it was just an area about three feet long that contained the ragworts, but it does illustrate a potential problem with this treatment method.  Any green plant still actively growing will fall victim to the glyphosate.  Before using this method of grass control it is essential that you know what other plants might be susceptible to the spray.  Then a decision can be made as to whether those plants should be sacrificed in order to remove the grass.  In this case, Golden Ragworts are quite common here and will quickly move back into their former haunt.

Other species are taking full advantage of their life without competition.  These Wingstem plants are out to set an all time height record.

The area along this trail used to contain a great stand of Monarda fistulosa.  The Monarda suddenly disappeared a few years ago.  It’s been slowly recovering and shows no damage from the glyphosate treatment.  I’m hoping that a few more years will find it back in its glory.

I’ve tried the December applied glyphosate treatment in the past on small, nine or twelve square foot plots.  One potential problem is leaving bare ground into which invasive plants can get a foothold. This is especially true with extremely thick stands of grass.  If native species cover less than half of the treated area, there is a high likelihood that colonizing weed species will appear on the site.  Teasel, Johnson Grass and Canada Thistle are some that are problems in this area.  Native annuals, such as the Giant Ragweed shown here, also take advantage of the exposed ground.  Giant Ragweed has always been a part of the flora along this section of trail and doesn’t cause me much concern.  It may be a bit more prevalent for a couple of years, but will soon return to its normal scattering of plants.

The native prairie grasses suffer no damage.  Their top growth has already died back by the time the glyphosate is sprayed.

This section of trail shows a healthy Indian Grass border.  The grass will be leaning in and just about closing the trail by September, but it doesn’t bother me as long as it’s native.

The next step in controlling the invasive grasses will be to move away from the trail and into the field.  I’ll monitor the area along the trail through the summer and if things seem to go well, I’ll treat some larger sections of the field this winter.

Johnson Grass

There are some plants that are recognized by many people as being noxious weeds. One of those is Johnson Grass. These towering grass plants with their broad strapping leaves are a major weed of agricultural fields and cost farmers a lot of money each year in spray costs and loss of production. Seeds travel widely in flood water and as passengers on farm machinery. If you are trying to convince people that management for native plants is a proper thing to do, you definitely don’t want such a well known weed growing where everyone can see it. I battle with this plant every year and most of my trouble is within sight of the road. New seed is regularly deposited on the roadside by farm equipment, road maintenance equipment and vehicles that snag plants crowding the edge of the road.

The origin of one patch of Johnson Grass is something of a mystery. It’s a fairly new infestation, but it’s nowhere near a road. It sprang up on the site of a patch of Poison Hemlock that I eradicated several years ago. The hemlock is now gone, but Johnson Grass has taken its place. I know that the bare ground resulting from the loss of the hemlock was perfect for colonizing Johnson Grass, but I don’t know where the seed came from.

Fortunately, Johnson Grass is not found in the established high quality prairies, so I don’t have to worry about protecting rare plants when I go after the weed. An easy way to destroy small patches is to mow the grass in late July, wait for the grass to shoot back up and spray it with glyphosate herbicide.

Johnson Grass regrows much more quickly than most of the other plants, so it’s possible to spray the site without killing everything else. Even if everything else dies, that’s better than letting the Johnson Grass live. In the thickest patches of Johnson Grass, there’s really not much else growing anyway.

For patches this size, I use a backpack sprayer with a flat fan spray nozzle. This gives good coverage on the target plant and makes for a more controlled placement of the herbicide. That spray wand looks like the heat ray weapon on the Martian flying machines in the original War of the Worlds movie. Maybe if I dye the spray red, it will give the plants more of a scare.

Why I Spray Herbicide

I never walked Blue Jay Barrens before buying it. Of course, it wasn’t called Blue Jay Barrens then, it was just an old, rundown farm. My wife and I looked at the house and decided it was acceptable, but all I knew about the land was that I was getting a 100 acre back yard in a geologically unique area. I had no intention of doing any real management on the property. I was just sure that there was a lifetimes worth of fascinating nature out there to be discovered.

Things changed when I began finding rare plant species that had their continued existence threatened by shading or crowding by other species. One of the guiding principles of conservation planning is to put the land to the use for which it is best suited and this land was proving to be best suited to rare species and ecosystems. As a professional planner and the owner of the property, I felt responsible for seeing that the rare plants were protected. Besides, I thought it was all fascinating.

This was all pre-internet, so I didn’t have easy access to information. Restoration Ecology was a developing science and it was hard to find anyone that could give you sound advice. Wildlife managers recommended planting all sorts of exotic plants, but that didn’t seem to be quite the right thing for this property. I started gathering everything I could find about rare ecosystems and their management and developed my first management plan. The greatest management need was to remove the plants that threatened the rare species I was discovering.

People are often surprised when they ask me what kind of work I do to maintain rare ecosystems and I reply that I kill plants. Except for some time spent maintaining the trails, all of the physical work I do is related to removing unwanted plants. I cut and I pull and I spray all manner of aggressive plant life in order improve conditions for the rare natives. Most of the plants I’m after are non-native invasive species, but I also remove common native species in favor of the rarities. If I had a choice, I’d just let nature take it’s course, but we’ve made such a mess of our native ecosystems that I can’t see myself not doing all I can to save what I’m able to save.

I thought a long time about the use of chemicals to control invasive plants. After much study and thought, I decided that glyphosate herbicide, commonly known by the brand name Roundup, would benefit my management efforts. I chose to use glyphosate because of its benign interactions with the ecosystem. The glyphosate molecule is absorbed by plants and is designed to bond with a specific enzyme within the plant. This glyphosate bond prohibits the enzyme from forming a normal bond that would allow production of amino acids responsible for making proteins required for plant growth. The result is a plant that starves to death. These enzymes are only found in plants, so glyphosate only interacts with plants.

Glyphosate does form a second bond and that is with clay particles. This bond is formed when any glyphosate touches the soil and is so strong that the glyphosate is essentially neutralized. Plant roots are unable to absorb glyphosate bound to clay, so neighboring plants are not affected. In order to work, glyphosate must be applied directly to an actively growing plant. The glyphosate bound to the soil is degraded by microorganisms into naturally occurring soil substances.

Without the use of glyphosate, many invasive plants would be uncontrollable and I would have to face the fact that much of what is special about Blue Jay Barrens was destined to be lost. NOTE: The photos used in this post show areas of grass and rare plants that would not exist today if succession had been allowed to follow its natural course during the past 25 years.