All this past week I continued to spray small buckthorn shoots with Garlon 3A. I was somewhat stunned by how many there were.
The site I was working on (Unit 10) was cleared in 2000-2001 and has been burned annually ever since. Over the past three years prairie grasses have become established in the more open areas, and there are lots of good forbs, such as showy goldenrod, cream gentian, culver's root, stiff goldenrod, zig zag goldenrod, elm-leaf goldenrod, etc.
But buckthorn persists. Some of the plants I sprayed were about shin- to knee-high, with multiple stems, but there were quite a few that were almost rosettes, barely ankle height, like those in the photo above. These look like seedlings to me, but I find it hard to believe that there is still a seed bank in this unit. There hasn't been a berry formed here for 7 or 8 years.
There is so little data about basic ecology of buckthorn. There was some Canadian research on the extent of the seed bank, but no long-term research on how long the seed bank lasts. I am waiting for some faculty member at UW-Madison to take up the challenge and initiate a long-term program on buckthorn. The Arboretum has large populations of buckthorn, including some that are still making berries. I could think of some great research projects here!
Also, I keep reading various web sites and weed manuals giving me misinformation about control. For instance, "buckthorn can be controlled by burning." Obviously wrong, if my observations in Unit 10 have any meaning.
In the meantime, I am carefully marking all the areas I am treating so I can return to them next year and see what has happened.
The photo below gives a little idea of what we may be up against. This was a buckthorn plant I pulled up by the roots from wet soil after a rain. The dark stem in the lower part of the photo looks like a rhizome to me. In fact, if I can get the right kind of soil conditions, I can pull up structures like this that are 3-4 feet long, and have other plants at their far end. The fibrous root network makes me wonder how much herbicide we have to get down there to kill this guy off.
Follow this link to see what the site I have been working on looks like right now.
I think you would agree it looks great. But get down on the ground and look at all those buckthorn plants!!
I'm under the impression that if there are ample amounts of grasses in the areas of buckthorn infestation, that burning would eventually control this pest. Is this true in your savannas? From my experience, autumn olive and buckthorn are always a problem where forbs outweigh grasses because the forbs don't burn as hot or really at all when compared to grasses like wildrye and bluestem. If this is true, maybe it would be helpful (and sustainable) in the long run to focus energy on establishing grasses in the infested areas rather than the labor-intensive task of cutting and treating stems?
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