Buckthorn eradication: results of a five year study
Because of buckthorn's importance, there have been many earlier posts from Tom's Blog. A list of these posts, with URLs, can be found at this link.
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Buckthorn is probably the most difficult shrub to get rid of in prairie and savanna restoration (it’s at the top of IPAW’s list). Because of its strong allelopathic nature, if unchecked it can form extensive monocultures.
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Buckthorn is probably the most difficult shrub to get rid of in prairie and savanna restoration (it’s at the top of IPAW’s list). Because of its strong allelopathic nature, if unchecked it can form extensive monocultures.
Removal of buckthorn requires the use of an herbicide,
either as a basal bark or cut stem application. Although these treatments are
very effective, they do not eradicate an infestation for two reasons:
- There is almost always an extensive seed bank. This is fairly easy to control, and only persists for several years.
- There are numerous dormant root masses capable of sending up new shoots, and these are a much more difficult problem. Experience has shown that these viable structures can remain alive for at least 15 years, perhaps longer, even if any new shoots they form are mowed or top-killed by annual fire.
What I am reporting here are the results of a long-term
study I carried out at Pleasant Valley Conservancy. The area used was a small
part of a much larger bur oak savanna which was first cleared of buckthorn in
the 1999-2000 period. The initial fairly large-diameter shrubs were killed by
basal bark treatment with Garlon 4 in oil. After the shrubs had died (which
took about two years) they were removed when the savanna was restored. Since
then, the site has been burned annually.
Despite annual burns, new buckthorn shoots kept appearing
every year. Each shoot was part of an extensive underground root mass. Five
years ago I decided to see how long it would take to get rid of them. I think I
have finally succeeded.
Starting in 2010 I canvassed the site carefully and sprayed with Garlon each buckthorn shoot, counting as I proceeded. In the three
early years, when there were lots of shoots, I returned over and over again at
2-3 week intervals. At the end of the season, I made sure that there were no
live buckthorn shoots left.
The table shows the results. I should emphasize that the
effectiveness of my spraying is not in question. Thus, a shoot found in 2012 is
not one that had been sprayed in 2011 and not killed. My conclusion is that in
this small area there were many dormant root masses, but not all of them left
dormancy the same year.
Year
|
Buckthorn shoots
sprayed in study area
|
Year total
|
2010
|
not
recorded
|
>300
|
2011
|
12+30+71+35+27
|
175
|
2012
|
17+18+55+5+44+20+82
|
241
|
2013
|
6+7+8
|
21
|
2014
|
0
|
0
|
Another conclusion is that it is possible to eradicate a
site of buckthorn, but the site must be revisited in multiple years.
One might ask what effect this multiple spraying might have
on the natural flora. That’s a lot of Garlon! I should emphasize that I was
careful with my spraying, making sure that nearby “good” plants were not
treated. The table below is the species
check list I made this year, when no spraying had been done. The diversity is
satisfyingly high! Note the presence of Gentiana
alba, a State Threatened species. There are actually two separate patches
of this species, one of which has numerous stems, and both patches flowered.
Latin name
|
Common name
|
Actaea rubra
|
Red baneberry
|
Agrimonia gryposepala
|
Tall agrimony
|
Allium cernuum
|
Nodding wild onion
|
Amorpha canescens
|
Lead-plant
|
Andropogon gerardii
|
Big bluestem
|
Anemone virginiana
|
Woodland thimbleweed
|
Asclepias syriaca
|
Common milkweed
|
Asclepias verticillata
|
Whorled milkweed
|
Aster ericoides
|
Heath aster
|
Aster novae-angliae
|
New England aster
|
Aster sagittifolius
|
Arrow-leaved aster
|
Campanula americana
|
Tall bellflower
|
Desmodium glutinosum
|
Pointed tick-trefoil
|
Desmodium illinoense
|
Illinois tick-trefoil
|
Elymus hystrix
|
Bottlebrush grass
|
Eupatorium altissimum
|
Tall boneset
|
Eupatorium purpureum
|
Purple joe-pye weed
|
Gentiana alba
|
Cream gentian
|
Gentianella quinquefolia
|
Stiff gentian
|
Heliopsis helianthoides
|
Ox-eye sunflower
|
Hieracium kalmii
|
Canada hawkweed
|
Lactuca canadensis
|
Tall lettuce
|
Monarda fistulosa
|
Wild bergamot
|
Ratibida pinnata
|
Yellow coneflower
|
Rudbeckia hirta
|
Black-eyed Susan
|
Schizachyrium scoparium
|
Little bluestem
|
Silphium integrifolium
|
Rosinweed
|
Silphium terebinthinaceum
|
Prairie dock
|
Solidago rigida
|
Stiff goldenrod
|
Solidago speciosa
|
Showy goldenrod
|
Sorghastrum nutans
|
Indian grass
|
Sporobolus heterolepis
|
Prairie dropseed
|
Toxicodendron radicans
|
Poison ivy
|
Tradescantia ohiensis
|
Common spiderwort
|
Verbena stricta
|
Hoary vervain
|
Zizia aurea
|
Golden Alexander
|
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