In many instances, the simple task of hand pulling is the
most effective way of eliminating unwanted plants. This pile of invasive Sweet Clover, Wild
Carrot and Oxeye Daisy was removed from a one acre barrens opening this past
summer. Remnants of last year’s plant
collection can be seen beneath this year’s greenery.
This area is typical of the Blue Jay Barrens openings. Steep, shallow, extremely dry soils present
numerous challenges to plant growth.
Invasive plants can become established, but not with the ease or
rapidity demonstrated in the former cropland areas.
The welcome mat for invasive plants is in the form of
exposed soil, a defining quality of barrens sites. A seedling that overcomes the other obstacles
can grow undisturbed by competing vegetation.
Colonization may be slow, but a persistent species can build quite a
population over a period of years.
This is my fourth year of pulling Sweet Clover and Wild
Carrot from this site. Plant removal is
quite an effective control method for these species. They are biennials that form a rosette in
year one, then produce seed and die in year two. If you can halt the production of seed, you
can eliminate new generations of plants.
An annual maintenance visit to each site is still necessary to catch any
new plants that may emerge. Sites that I
began treating 10+ years ago, now have only a few Sweet Clover plants per acre
and virtually no Wild Carrot. Sweet
Clover seed is notorious for persisting in the soil seed bank and remaining
viable for decades after falling from the plant. In order for the seeds to survive for that
length of time, they need to be incorporated within the soil profile where they
are protected by the ravages of weather and other environmental factors. I’ve noticed that most of the studies of
Sweet Clover seed longevity have been completed on former crop ground, where fresh
clover seed could have been neatly buried by common agricultural tillage
practices. Seed produced on the barrens
is unlikely to get buried to a depth that would allow it to be protected for extended
periods of time. The seed here stays
near the surface and either germinates or dies, so removing plants rapidly
produces positive results.
I’ve also been getting more hands-on with the invasive Oxeye
Daisy.
I’m still looking for an effective control method in the old
crop fields. The plant is too numerous
and too crowded by prairie plants to be easily removed by hand. There are also too many quality native plants
here to make herbicides a viable control alternative.
This Ragged Fringed Orchid, Habenaria lacera, visible in the
center or the preceding photo, is just one of many unassuming plants that has
found itself being pressured by Oxeye Daisy.
Oxeye Daisy has been slowly making its way into the
barrens. I hand pulled the daisy from a few test areas two years ago, with favorable results. This year I pulled Oxeye Daisy right along
with the clover and carrot. New daisy
plants begin as a basal rosette. When
they’ve stored enough energy, they send up a flower stalk.
Oxeye Daisy removal is totally effective if you leave no
viable plant parts in the soil. This
young plant pulled easily and shows no evidence of missing underground parts.
A slightly older plant displays the start of a rhizome that
would eventually give rise to new plants.
The stub of a broken rhizome on a pulled plant means that a viable plant
part has been left behind to grow a new plant next year.
A single plant will eventually produce a thick colony of
plants. This plant has a single tall
flower stalk and three healthy rhizomes.
I think I’ll be able to successfully eliminate Oxeye Daisy from the more
rugged barren sites, but I’m still looking for viable control options in other
areas.
I’m still collecting seed heads from Teasel in early August,
but I also now treat random plants while I’m out doing other invasive species
work. A shot of glyphosate into the
center of a basal rosette will kill the plant, or at least damage it enough
that it never produces a flower. Tall
plants can be cut and the stump given a little spray of glyphosate. These two methods would be difficult to apply
on a large scale, but are handy to use when finding a handful of plants in an
isolated location. It’s easier to
eliminate the plant at the time it is found, than it is to remember to revisit that
spot later on to collect seed heads.
Of course, I’m always interested in animals that feed on
invasive plants. I found this stalk
borer inside the base of a tall Teasel plant.
I doubt the borer would have killed the plant, but similar borers might
be the reason I occasionally find plants broken off at the base. These broken plants may lay down and hide in
the tall grass, but the flower stalks turn upward and still produce plenty of
seeds. Since I have trouble finding
these fallen plants, the borer may actually be hindering my control
efforts. Despite minor setbacks, I’m
sure that I can eventually get most of these invasive plants under control.