Story County, IA Landscaping Rules: Tree Removal & Heritage Trees (2026)

Under Story County Code of Ordinances § 88.05(1)(B), the significant-tree standard applies to development, meaning zoning and grading permits, conditional use permits, commercial site plans and subdivisions of more than two development lots; it does not apply to routine tree/shrub management such as thinning or removing invasive or dead and dying trees. A significant tree is a native, deciduous tree with a caliper greater than four inches measured four feet off the ground, or a native coniferous tree taller than fifteen feet; a significant native shrub has a basal diameter of three inches. Exempt from the protection are low-quality replantings identified through historic aerial imagery, dead or hazardous trees, trees blocking sight lines at driveways and intersections, and species the Iowa DNR lists as invasive.

Residential zoning and grading permits, or permits on subdivision lots platted before the ordinance, may impact up to one acre of significant trees or shrubs without triggering mitigation; impact beyond one acre requires it. Commercial site plans, conditional use permits and subdivisions of more than two lots may impact up to 15 percent or five acres of wooded acreage, whichever is less, before mitigation applies. Where mitigation is required, trees or shrubs must be replaced at a minimum 1:1 ratio, up to 6:1 for commercial and larger subdivision projects if a qualified professional recommends it based on species and size, plus a 20 percent mortality buffer added to the replacement count. Replacement plants must be primarily native species, planted on-site or at an approved alternative site within the county, and paid for at the applicant's expense. Residential replacement plans may be approved administratively by the Planning and Development Director; larger commercial and subdivision mitigation plans require Board of Supervisors approval after a Story County Conservation Board recommendation.