Treating Invasives

I took advantage of the mild weather during the first half of November to search out and eliminate some invasive shrubs.  Most of what I find now are young plants that have not matured enough to produce seed.  Birds will continue to bring in fresh seeds, and plants resulting from those seeds are what I am primarily dealing with now.  Birds that left seeds on this spot had a varied diet that resulted in a cluster of my four primary target plants.  Clockwise from upper center are Autumn Olive, Multiflora Rose, Bush Honeysuckle, and Japanese Barberry.

Japanese Barberry is a recent invader of Blue Jay Barrens and has not become very well established.  By the time the first Barberry plants began showing up, I had already begun dealing with invasive shrubs.  Only a few got up to fruiting size before they were discovered and removed.  This species is easy to control by stump spraying with glyphosate.  Even a maximum recommended dilution of the chemical is enough to kill the roots.

I’ve still got a couple of small patches that continue to produce a wealth of new Bush Honeysuckle plants each year.  Fortunately, the glyphosate stump treatment quite effectively kills this invader.  It’s discouraging to annually deal with so many new plants, but the sites are small and the number of plants continues to decrease.  Five years ago, the new Honeysuckle growth here was thick enough to block the view of the ground, so I am making progress.  I have to remind myself of that fact each time I work here.

Only one larger Honeysuckle specimen was found this year.  It was roughly six feet high, but was not old enough to produce fruit.  Last year, this shrub would have been only two or three feet tall and would have been easy to miss in its position on the lower slope of the creek bank.  I don’t mind finding an occasional large plant, as long as I catch it before it has a chance develop fruit.

Autumn Olive is the most difficult shrub to control at Blue Jay Barrens.  I use a stump treatment of undiluted glyphosate 41% concentrate solution.  This method is quite effective as long as the plant being treated is displaying healthy, bright green leaves.  Once the leaves begin to yellow and drop, it becomes more difficult to get a good kill.

Older, fruit bearing  Autumn Olive specimens can be killed by the same stump treatment, but there is a high likelihood of root sprouts appearing the next growing season.  It may take a couple of years to eliminate the sprouts.  Seedlings also tend to recur for several years following the death of the large shrub.  Birds feeding on the fruit, drop some of the seeds from the previous day’s feast.  Some of these seeds are ready to sprout immediately, while some may wait through a few seasons before germinating.  The good thing is that no matter where the new plants are coming from, their numbers tend to lessen with each passing year.

Autumn Olive can grow so rapidly that they sometimes seem to appear from nowhere.  This area of Indian Grass was mowed last November.  Small Autumn Olive plants, hidden in the thick grass, were cut off a few inches above ground level.  With a healthy root system already in place, the regrowth from those cut stems reached six or seven feet high in one season.

This is what the base of that plant looked like.  The dead stub in the center of the stem cluster is the single stem that was cut off last year.  It’s obvious that mowing is no way to control Autumn Olive.

To effectively treat young Autumn Olive, you must cut the stem flush with the ground.  The problem is that the stem you see may not be rising directly above the root.  Autumn Olive commonly produces a horizontal stem that later gives rise to the aerial branches.  This horizontal stem is often hidden by thatch or neighboring plants.  In the photo, the stem to the left was attached to the root and the vertical shoot emerged three inches away.  Cutting and spraying at the base of the vertical shoot would most likely not kill the plant.

I am also beginning an assault on the invasive Crown Vetch.  It was planted along the road about 40 years ago, but only recently has it begun to show up out in the fields. 

I was going to spray the Autumn Olive with Clopyralid this summer, but neighboring vegetation made it impossible to get the spray through to the vetch leaves.  Instead of spraying, I went around and identified the locations of all infestations, about ten in all.  I mowed them this fall and will do my spraying next spring when the vetch begins growing.  I guess I don’t have to worry about running out of invasives to deal with.