Conservation Corner: Experiments with chicken tractors to manage orange hawkweed

Orange hawkweed is unlike many invasive plants in that it spreads by rhizomes, stolons (runners), and seeds, secretes chemicals that inhibit the growth of other plants, and thrives in shady and intact ecosystems (most invasive plants require disturbed ground and full sun). Mechanical and manual control methods, such as digging, mowing, and smothering are largely ineffective, leaving herbicide as the only treatment option. However, herbicides often come with concerns and public pushback. This experiment tried a novel approach to managing invasive plants, specifically orange hawkweed: chickens.

Inspiration for the project came from an observation of free-ranging chickens clearing a dense patch of orange hawkweed in two years, while leaving the native fireweed meadow community intact. This project used chickens kept in a smaller space and for shorter duration to see if similar results could be achieved. Plant diversity and abundance were measured before and after chickens were allowed to graze in the study plots for varying durations.

Three 24-square-foot chicken tractors (mobile coops), each housing four chickens, were placed on plots of lawn thick with orange hawkweed. Each chicken tractor was moved to a new plot at intervals of two, four, or six weeks. We hypothesized that two weeks wouldn’t be long enough for chickens to effectively remove rhizomes, stolons, and seeds; this turned out to be accurate. After two weeks in one place, chickens cleared all vegetation, but once moved, vegetation quickly grew back. After four weeks with chickens, vegetation took another four weeks to regrow and remained sparse. After six weeks, very few plants resprouted for the next six weeks. To ensure the chickens’ welfare, the tractors remained in one place no longer than six weeks. Based on these outcomes, we concluded that four weeks is the ideal interval for removing vegetation and keeping a happy flock, at a stocking rate of four hens in a 24-square-foot area.

At the three plots with chickens for four or six weeks, plant regrowth was minimal and dominated by grasses and common dandelion. At the remaining five plots, each with chickens for two weeks, results were mixed. Two plots showed the same trend of regrowth dominated by grasses and common dandelion, while three plots had more regrowth of grasses and orange hawkweed.

This technique could be a viable alternative to chemical treatments of invasive plants, like orange hawkweed. The local community hosts many backyard chicken coops and small farms, which means chickens could easily be put to work managing invasive species, in addition to providing eggs. This experiment used hens that were no longer laying eggs, and highlights a use for “retired” hens, rather than culling.

While it’s well known that chickens will clear vegetation down the bare ground, all the evidence we could find prior to this experiment was anecdotal. To our knowledge, this is the first controlled and documented experiment with chicken tractors that provides quantifiable results.

The Conservation Corner is monthly column with the USDA-NRCS Homer Office. This month’s author is Casey Greenstein of Homer Soil and Water Conservation District. This project was funded in part by the USDA National Institute of Food and Agriculture through the Western Integrated Pest Management Center, grant number 2022-70006-38003.