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.