Tag Archives: invasive species

Piehl’s Dye Experiment and Implications for Herbicide Treatment

Are you sure you want to apply herbicide to this plant?I never thought about this when applying herbicide to cut woody vegetation, or even herbaceous weeds, but we should be watching out for nearby parasitic and hemiparasitic plants. Wood-betony (Pedicularis canadensis), for example, taps into relatives of a number of species we’re often trying to suppress or eliminate from ecological restoration projects (e.g., aspen, cedar, honeysuckle, maple, pine, sumac). Martin Piehl’s techniques for studying the relationship between hemiparasites and host plants included tracer experiments where he applied a water-soluble dye to cut trees and watched for its appearance in nearby hemiparasites. “After several days, in the case of the aspen host, a high enough concentration of dye was taken into the leaves of the parasite to cause them to wither and die …” Granted, he was applying a large amount of the chemical. But it is certainly worth keeping in mind. Fortunately, most of the invasive plants I’ve had to apply herbicide to are far from our wood-betony colony.

If anyone has personal experience with this, please let me know. I’d also like to compile a list of parasites and hemiparasites found in Wisconsin. I was actually surprised when I first learned wood-betony is a hemiparasite. There could be another parasite or hemiparasite connected to the honeysuckle (Lonicera spp.) I intend to cut and apply herbicide to later.


Piehl, MA. 1963. Mode of attachment, haustorium structure, and hosts of Pedicularis canadensis. American Journal of Botany 50(10): 978-985.


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• firm or obstinate continuance in a course of action in spite of difficulty or opposition

• the continued or prolonged existence of something

ORIGIN mid 16th cent.: from French persistance, from the verb persister; influenced in spelling by Latin persistent- ‘continuing steadfastly.’

— New Oxford American Dictionary

We didn’t fully grasp the nature of the path we were about to embark upon when we asked Michael Anderson to burn our prairie remnant and about two acres of surrounding grassland ten years ago. The process appeared simple enough: restore fire to the land so native plants might flourish. I knew very little about native plants and ecology when we started. Actually, I didn’t think much about native plants, especially prairie plants, before Blue Mounds Area Project ecologist Bob Wernerehl told us about the shortgrass prairie remnant growing near our new house. And I certainly didn’t think much about exotic plants and their dreadfully wicked ways. But I was about to learn a lot.

There were the Years of the Thistle, when we invested dozens of hours trying to eradicate solid patches of thistle (Carduus spp. and Cirsium spp.) that firmly stood their ground. We used string trimmers, a lawn mower, a machete, loppers, and, finally, a propane torch to evict them. I seriously wondered whether it was worth the effort. Family and friends had to be called in as reinforcements to work quickly enough to prevent more seed from falling on the ground.

There were the Years of the Sweet Clover, when we invested dozens of hours trying to eradicate solid patches of sweet clover (Melilotus alba) that were advancing toward the relatively pristine prairie remnant forming the core of our project. Year after year, we tried to pull it before it dropped more seed and finally had to ask Errol Jung to mow it down to buy us a little more time. Ideally, a person burns the area two springs in a row to largely eradicate sweet clover, but the weather never cooperated and the bare ground under the thistle and sweet clover interfered with the spread of fire. Again, I wondered whether it was worth the effort.

Then there were the Years of the Wild Parsnip, when we invested dozens of hours pulling and cutting wild parsnip (Pastinaca sativa), preferably late in the day to protect ourselves from the phototoxic sap. I started by pulling the plants a day or so after it rained—or cutting their roots just below the soil surface—and hauling them to the compost pile to avoid dropping viable seed on the ground, but Merel Black offered some sound advice for accelerating the process: cut or mow the plants just before the seeds harden and leave them lay where they fall … the seed aren’t viable and you’ll see far less wild parsnip next year. It really works!

Then there was the Year of Success. Yes, success! Persistence—“continuing steadfastly”—does yield results …

Pale Purple Coneflower

No thistle, sweet clover, or wild parsnip!

Most gardeners know populations of weeds decline if a person breaks the cycle of seed production by annuals and biennials, but it is more than a bit hard to believe when someone is trying to deplete a seed bank that has accumulated for years and might lie dormant for a decade. And when those owning the land around you don’t appear concerned about aggressive exotic plants, it seems futile.

This year, however, we had to dedicate only a few hours to pulling thistle, pulling sweet clover, and cutting wild parsnip. We dedicated just a few hours to surveying two acres of grassland, scanning for aggressive exotic plants, and swiftly removing them. Sure, there are still weeds, there are still plants that don’t belong there. We haven’t burned the area for several years and woody plants—e.g., honeysuckle (Lonicera spp.) and box elder (Acer negundo)—are moving in. I’ve also noticed a few teasel (Discus fullonum). But this is all manageable and we now have some time for expanding our project.

Of course, there’s more to preserving a prairie remnant than controlling aggressive exotic plants. What about enriching the area? What about biodiversity? Well, that’s the other half of the success story. While we were busy tackling thistle, sweet clover, wild parsnip, honeysuckle, and a few other species, we were also collecting and scattering seeds of native plants. As I walked back and forth on my search and destroy mission over the past few weeks, I saw tiny leadplant (Amorpha canescens) where I didn’t expect them and previously absent Illinois tick-trefoil (Desmodium illinoense) scattered throughout the two acres. There’s purple prairie clover (Dalea purpurea) blooming everywhere, far beyond the remnant where we first found it. pale purple coneflower (Echinacea pallida) is expanding its range beyond the small corner where we put just a few plants years ago. Prairie dock (Silphium terebinthinaceum) are reliably sending up flower buds where I previously spent a cool damp November afternoon poking seed into the earth. Butterfly weed (Asclepius tuberosa) is very scarce, but finally establishing a roothold. And clumps of prairie dropseed (Sporobolus heteropolis), little bluestem (Schizachyrium scoparium), big bluestem (Andropogon gerardii), and Indian grass (Sorghastrum nutans) are displacing Eurasian grasses.

The continuous steadfast removal of aggressive exotic plants before they produced more seed yielded results. Learning from others and applying their advice yielded results. Regular collection and scattering of seeds of native plants — though one might not notice until several years later—yielded results. I no longer have to wonder whether it is worth the effort.

This is important … persistence and no longer wondering whether we’ll actually accomplish our goal, for there’s another area containing native plants we’d like to liberate. There’s leadplant, thimbleweed (not sure which one), wild bergamot (Monarda fistulosa), various asters, prairie alumroot (Heuchera richardsonii), and others. It too covers about two acres. The honeysuckle are running rampant, but we’ve managed to reduce the population of thistle and sweet clover. And the wild parsnip is retreating. Errol Jung mowed the infested area last week, which should substantially reduce seed production. BUT … there’s also crown vetch (Coronilla varia), an extremely aggressive exotic plant, extending its tendrils into every nook and cranny. This is a tricky one, as the most effective herbicide for destroying this perennial happens to kill the native leadplant and members of the aster family. I just have to remind myself: persistence will yield results.

And the ultimate result—through our combined work—is persistence of our natural biodiversity, which makes it more than worth the effort.

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Book Review: Bringing Nature Home

Bringing Nature HomeBringing Nature Home
by Douglas W. Tallamy
Timber Press, 2007

Douglas Tallamy, Professor of Entomology and Wildlife Ecology of the University of Delaware presents an open and shut case for not only planting native plants, but going the extra mile to eradicate the alien plants in your yard or on your land. After you read this book you’ll find yourself compelled to spread the word, not simply for aesthetic or practical reasons, but to save all life on Earth. Seriously, that’s how I felt after reading just a few pages.

Tallamy’s flash of insight arrived when he and his wife moved to a ten-acre farm in Pennsylvania. As an entomologist, he was startled by the lack of insect damage—and insect life—on the exotic plants that were aggressively replacing the native vegetation. His investigation of exactly who eats what—and why exotic plants are truly dangerous—is presented in this book.

Here’s the first important fact. Herbivorous insects convert plants into food for numerous amphibians, reptiles, birds, and mammals. For example, fully 96 percent—yes, 96 percent!—of terrestrial North American birds rely on insects and other arthropods, usually the spiders that eat insects, to feed their young.

Here’s the second important fact. Exotic plants, often valued because they are not touched by insects, support a relatively small number of insect species. What does this mean? Less insect biomass. For example, the author’s research in Pennsylvania showed that native woody plants support 35 times more caterpillar biomass, the preferred source of protein for bird nestlings, than alien woody plants provide. It is an understatement to point out that this can make the difference between a successful breeding season and severe decline of a local population.

After explaining why insects can’t eat alien plants, providing a brief overview of the true cost of exotic ornamentals, and letting us know why our gardens are better off if we actually feed the local insects, the author launches into a 40-page whirlwind tour of North American woody plants that sustain insects and, indirectly, other organisms. Why woody plants? Folks are already interested in providing nectar and pollen for adult butterflies and moths, but there’s not so much interest in feeding the caterpillars… and you can’t have one without the other. This section of the book is enjoyable for the natural history alone. The reader learns that oaks (which are preferred by 105 insect species) can “churn out caterpillars from May to October”, bats eat the adult stage of the tent caterpillars that thrive on cherry and plum trees, and forest birds benefit immensely during outbreaks of spruce budworm (an important food for nestlings).

Douglas Tallamy continues with a 60-page chapter entitled “What Does Bird Food Look Like?” Again, it is worth reading for the natural history alone. But the numerous anecdotes and references to research—fully documented if one wishes to read the original journal articles—drive home the point that much of the life we see flying and crawling around us is quite dependent upon an army of insect and other arthropod species consuming plants… and one another. The reader gets to meet some familiar and not so familiar herbivores and predators and learn about their roles in ecological communities. There are exceptional close-up colored photographs accompanying the descriptions and I found my self saying over and over, “So that’s what I saw when I walking around last summer!” I now I want to learn even more about these critters.

The author concludes with a FAQ section that helps us understand why insect or bird activity around a given alien plant is not a sign that all is well and offers some advice for winning over the neighbors who might object to your wild and insect-infested gardens.

This is not exactly a how-to book, but a motivational and inspirational book. Douglas Tallamy lives in Pennsylvania, is primarily interested in forests, and writes from his own experience. Not all the plants and insects listed in the appendix are found in the Midwest, but it certainly serves as an excellent starting point for your own investigation.

I encourage folks to read this book for several reasons. You’ll know why alien plants are a threat. You’ll know why you should always plant native species instead of alien species. You’ll be able to explain why to other people. And you might be motivated to look into what’s happening in your own region of the country and share the information with others before it is too late. I hope someone will write a similar book for the Midwest.

Most important, given the extent of fragmentation of habitat and numerous other threats to plant and animal species, the reader will walk away realizing that every garden, every plot of land, every container on your patio is essential for preserving the biodiversity around us.

According to Douglas Tallamy…

“But now, for the first time in its history, gardening has taken on a role that transcends the need of the gardener. Like it or not, gardeners have become important players in the management of our nation’s wildlife. It is now within the power of individual gardeners to do something that we all dream of doing: to “make a difference.” In this case, the “difference” will be to the future of biodiversity, to the native plants and animals of North America and the ecosystems that sustain them.”

I’d like to thank the Mound Vue Garden Club for donating a copy of this book to the Mount Horeb Public Library. I found it by chance while perusing the “new book” shelf and thoroughly enjoyed learning about this subject. I’ll be purchasing a copy for my home library.

This book review originally appeared in the Blue Mounds Area Project Summer 2009 newsletter. The Blue Mounds Area Project is a community-based organization that seeks to inspire, inform, and empower private landowners in the Southwestern Wisconsin region to enjoy, protect, and restore native biodiversity and ecosystem health.


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