Becoming the Bison

By Erica Place on July 12, 2024 in Blog

Ray Hamilton first noticed the strange plant atop the rocky, rolling peaks at Codfish Hollow Hill Prairie, a 60-acre parcel of remnant and reconstructed prairie near Maquoketa he and his wife Patti had purchased in 1984.

Ray became intimately familiar with the property, diligently removing trees that punctuated the grassland and taking inventory of the species around him while he worked. He created buffer zones around the native knolls, planting and spreading seeds with carefully selected site-specific genetics. With the help of others, he’d amassed an impressive list for the biological preserve he was stewarding: 100 prairie flower species, 20 species of grasses or sedges, 30 species of woodland flowers, 20 species of trees and shrubs and many bird, mammal, reptile and insect species that find haven in the habitat Ray and Patti have worked so hard to restore. But this plant was something new.

The stranger was a short-statured thistle with wavy leaves, markedly different than other thistles he knew, but his books and references gave few clues. When a bio foray — a weeklong effort by experts in the field to identify species in natural areas — was later scheduled for Jackson County, Ray decided to take in a sample, roots and all, for help with identification.

The verdict was that he had an “undulating thistle,” and Ray called it by that name for the decades that followed, not knowing if it was important.

“I knew it was growing among other high quality native prairie species, but not much was known about this thistle at the time,” remembers Ray. “I’d never heard anyone talk about this plant.”

As part of his lifelong effort to gather as much knowledge as he can about all the species calling Codfish Hollow home, Ray kept researching and noticed the undulating thistle was regularly referred to as aggressive and problematic. That wasn’t how it was behaving at Codfish Hollow. Some time later, after comparing pictures and descriptions in guides that just didn’t match up, Ray came to realize that it was a different species entirely: the Hill’s thistle.

Iowa has six species of native thistles, beloved by bees, birds and butterflies. Though they belong in this state, provide an important food source in late summer and fall and don’t pose any ecological issues, Iowa’s native thistles are still listed as “noxious weeds” under Iowa code. While a rule change within the last decade means landowners are no longer required to control these six species, the perception widely persists that all thistles are bad. Three of those six species are now also listed as species of special concern, including the Hill’s thistle.

Native to the upper Midwest and in primarily the eastern half of Iowa, Hill’s thistles (Cirsium pumilum var. hillii) are quickly disappearing from their range. They’re a short-lived perennial, typically blooming only once in their lifetime.

“I’ve seen some estimates where there are perhaps 4,000 individuals left across maybe 400 sites in the upper Midwest,” explains Ray.

The population as a whole is in severe decline, but at Codfish Hollow, they are thriving. Something about this prairie is unique.

Ray began marking the thistles with whatever he had handy — a scrap piece of wood, a rock, a bit of flagging. Over the years, Ray observed the thistles were congregated in specific areas — where he’d cleared brush, driven the tractor or dragged equipment; spots that had seen significant disturbance.

“The thistles were doing very well in areas that honestly had been completely trampled,” says Ray.

Curiosity warranted an educated experiment. One day, Ray hooked a mower up to his tractor and set off through the prairie, leaving a mostly vegetation-free swath in his wake. Sure enough, in the next year or two, Hill’s thistles took root in the mowed path. He continued monitoring areas where he thought Hill’s thistle might pop up, carefully flagging every young thistle he found.

Codfish Hollow is now more than dotted with flags. Leaned against the fence he built around the newest 100 or so baby plants, Ray beams knowing he’s cracked the code for Hill’s thistle regeneration. It’s something trained ecologists haven’t yet been able to emulate. He doesn’t know whether it’s the roughed-up and compacted soil, the lack of competition, the increased sunlight or a combination of all three, but the Hill’s thistle is happy.

“I’m just trying to reproduce natural systems as carefully as I can,” says Ray.

Is a mower a natural system? Sort of. Ray’s referring to large herbivores like bison and elk that once moved across Iowa’s prairies in large herds, trampling the vegetation as they grazed. Ray’s mower is the new grazing, his tractor paths the new bison wallows.

Yes, there’s something unique about Codfish Hollow Hill Prairie. It’s Ray and Patti Hamilton and their stewardship philosophy.

Though it’s clear Ray is proud that the thistle is doing so well here while it’s struggling elsewhere, he’s also careful not to get too wrapped up in the needs of one thing. It’s a lesson he’d learned early on in his prairie stewardship after a visit from Dennis Schlict, author of  ‘The Butterflies of Iowa.’

Not long after the Hamilton’s purchased the property, Dennis documented the presence of a rare prairie-dependent butterfly called the Ottoe Skipper (Hesperia ottoe). The Ottoe Skipper spends its entire life cycle above ground, making it susceptible to fire or other disturbances if it has nowhere to escape. Dennis explained to Ray that if the whole prairie is burned at once, an entire population could be eliminated in a matter of seconds.

“Hearing that a simple choice — even with the best intentions — could have such enormous consequences was jarring,” remembers Ray.

It’s not just the butterflies on Ray’s mind, but other insects nestled in the vegetation, the slow-moving amphibians and reptiles, or the nest full of eggs tucked under a bunch of grass. Ray understands that each action holds positives and negatives, and he’s careful to never apply one practice to all of Codfish Hollow Hill Prairie. There are some practices he chooses to avoid entirely. But watch him decisively nip unwanted brush or pocket a handful of seeds, and you’ll see — he’s become the bison, grazing and churning the soil, controlling out-of-place plants and transporting seeds to new locations. He’s part and parcel of the ecosystem he cares for, making sure Codfish Hollow Hill Prairie is as balanced as it can be.