Final Report - Establishing monarch butterfly habitat on Iowa swine production sites

February 25, 2020

Cost-effective methods to establish and maintain monarch habitat

The eastern population of monarch butterflies has declined significantly over the past 20 years. Iowa is in the heart of the summer breeding range for this iconic insect. To support monarch butterfly conservation in Iowa, this study was conducted to evaluate cost-effective methods to establish and maintain monarch habitat – milkweeds and native wildflowers – on Iowa swine production confinement sites.

photo of proposed locations for monarch habitat demonstration plots

In 2016, twelve grass-dominated hog confinement sites in four central Iowa counties were prepared for planting monarch butterfly habitat. Glyphosate was applied twice during the growing season. A diverse, native seed mix was planted in early December of 2016 and changes in plant density, plant diversity, and monarch utilization were monitored during the summers of 2017 and 2018. Data was collected three times each summer in June, July and August, including baseline data beginning the summer before the habitat sites were planted with the native seed mix. Dr. Bob Hartzler, ISU Extension weed scientist, led the effort in collaboration with the interdisciplinary ISU monarch research team.

Survey teams recorded monarch presence, including eggs, caterpillars, and adults.  Increases in native flowers, native plant species diversity, and native milkweeds were recorded in addition to blooming plants, vegetation growth and thickness. Data analysis shows an increase in monarch eggs, caterpillars and adult butterflies using the new habitat from 2016 to 2018, as well as more blooms, more plant species, and more monarch activity. A free copy of the full research report is available to download from the National Pork Board.


  • Transitions from mowed turf to diverse native pollinator habitat require careful attention to site selection and site preparation to ensure successful establishment of native plant species at confinement facilities.

  • Annual weeds are very common in the early years of site establishment, but the greatest concern is aggressive perennial or biennial weeds that can outcompete native species. For this reason, it helps to know the site’s history and potential weed problems before converting from non-native, cool-season grasses to prairie pollinator habitat.

  • Best practices include multiple applications of glyphosate (spring, summer and fall) prior to a no-till, dormant planting of native seed, ideally mid-Nov to mid-Feb.

  • Successful establishment of monarch habitat at the swine production sites resulted in a quantifiable increase in adult and larval monarch and bee utilization.

  • With proper site selection and pre-planting preparation and maintenance, high- to medium-quality habitat plots can be established, at a reasonable cost, within a few years of planting.

The results show that hog confinement locations can provide suitable areas for monarch habitat conservation. This project appeared on the May 2019 cover of Iowa Pork Producer magazine. In video interviews with ISU Extension, farmers Ben Crawford and Tom Tiernan described what they have learned about monarch habitat. All videos are available at



photo of grass-dominated demonstration site prior to seeding native pollinator habitat


Photo of habitat demonstration site 2 years after seeding to native pollinator habitat