Iowa law prohibits mowing roadside ditches each year between March 15 and July 15, to protect ground-nesting birds and to prevent nest destruction.
Roadside ditches, while not optimal habitat, can be the only grassy habitat available in certain areas of the state for ground-nesting birds. As spring progresses, ground-nesting birds, like eastern and western meadowlarks, Dickcissels, field and song sparrows, quail, gray partridge, and pheasants, will use these marginal areas to incubate eggs and rear their young. The vegetation is also important to pollinators collecting nectar and for milkweed development that is critical for monarch caterpillars.
“It would help the cause if mowing was voluntarily delayed beyond the July 15 date to protect the late nesters and monarchs,” said Todd Bogenschutz, upland wildlife biologist for the Iowa DNR. He said an estimated 21 percent of pheasant nests are still active on July 15; that drops to 7 percent on August 1.
“It’s not the best habitat but we need to protect it for the wildlife that does depend on it.”
There are some exceptions to the law, however.
Mowing roadside vegetation on the right of way or medians of any primary highway, interstate highway or secondary road may be allowed prior to July 15 under the following exceptions:
- Within 200 yards of an inhabited dwelling.
- On right of way within one mile of the corporate limits of a city.
- To promote native species of vegetation or other long-lived and adaptable vegetation.
- To establish control of damaging insect populations, noxious weeds, and invasive plant species.
- For visibility and safety reasons.
- Within rest areas, weigh stations and wayside parks.
- Within 50 feet of a drainage tile or tile intake.
- For access to a mailbox or for other accessibility purposes.
- On right of way adjacent to agricultural demonstration or research plots.
Violations on county or secondary roads should be reported to the county engineer or roadside manager in the country where it occurred; violations on state highways or interstate highways should be directed to the Iowa Department of Transportation.
Mowing is allowed to resume after July 15.