O'Fallon, MO Landscaping Rules: Native Plants (2026)
Key Facts
- Minimum lot size for exemption
- More than 2 acres
- Must be
- Unimproved, no building
- Street buffer still required
- 8 inches, 20 feet from curb
- Detention basin conversion
- Requires City Engineer permit
- Converted basin mowing deadline
- November 1 annually
Summary
O'Fallon's eight-inch mowing rule doesn't apply to unimproved land over two acres kept as natural forest or native prairie grass, as long as the growth doesn't bother neighbors. Homeowners with a stormwater detention basin can also get a City permit to convert it to native grasses instead of turf.
The requirements of this Section shall not apply to any real property within the City limits which meets all of the following requirements: 1. Is not improved with any building or structure; 2. Is more than two (2) acres in size; 3. Is maintained as a natural forested area or natural grassland containing native or prairie grasses; and 4. Where the growth of such vegetation is compatible with the environment, enjoyment or use of nearby property and does not otherwise constitute a nuisance...
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: rev 4860992; v58 updated 2026-05-14; through 05-14-2026).
Full Breakdown
100(K) of the O'Fallon Code exempts property from the general eight-inch weed height standard when it meets four conditions together: the land carries no building or structure, it is more than two acres in size (measured by the individual lot or parcel, since multiple parcels under one owner cannot be combined to hit the threshold), it is maintained as a natural forested area or natural grassland containing native or prairie grasses, and the vegetation's growth is compatible with the enjoyment and use of nearby property so it does not itself become a nuisance.
Even a qualifying tract must still keep an eight-inch buffer along any public or private street for twenty feet back from the curb or pavement edge. 100 mowing requirement but the owner must submit and follow an alternative mowing schedule and mow the basin by November 1 each year.
Violations & Fines
A tract that no longer meets all four Section 220.100(K) conditions loses the exemption and reverts to the standard eight-inch limit, enforceable the same way as any other nuisance weed violation. For a converted detention basin, failing to mow by the November 1 deadline triggers enforcement under Section 220.100, the same nuisance-abatement process that leads to a special tax bill against the property.
Frequently Asked Questions
Can I keep part of my land as native prairie instead of mowing it?
Can I convert my backyard detention basin to native grasses?
Do multiple small lots I own combine to reach the two-acre exemption?
Sources & Official References
Other rules in O'Fallon
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