Iowa Code § 314.17: Mowing on interstates, primary highways, and secondary roads.

Mowing roadside vegetation on the rights-of-way or medians on any primary highway, interstate highway, or secondary road prior to July 15 is prohibited, except as follows:

1. Within two hundred yards of an inhabited dwelling.

2. On rights-of-way within one mile of the corporate limits of a city.

3. To promote native species of vegetation or other long-lived and adaptable vegetation.

4. To establish control of damaging insect populations, noxious weeds, and invasive plant species.

5. For visibility and safety reasons.

6. Within rest areas, weigh stations, and wayside parks.

7. Within fifty feet of a drainage tile or tile intake.

8. For access to a mailbox or for other accessibility purposes.

9. On rights-of-way adjacent to agricultural demonstration or research plots.