St. Louis County, MO Invasive Plant Rules: Prohibited Species (2026)
Key Facts
- Species banned outright
- Noxious weeds, invasive plants, nuisance plants
- Height exception
- Non-prohibited natives may exceed 8 inches
- Definition source
- Mo. Dept. of Conservation / USDA lists
- Max penalty
- $350 fine or 30 days jail, per lot per day
- Coverage area
- Unincorporated county, platted subdivisions +100 ft
Summary
Even where St. Louis County lets a property owner grow a managed natural landscape taller than the normal 8-inch mowing limit, Section 620.115 draws a hard line at species: noxious weeds and invasive or nuisance plants are barred outright, regardless of height, under the Managed Natural Landscapes Code, which pulls its species definitions straight from the county's Weed Control Code.
(b)Managed natural landscapes may include plants and grasses in excess of eight (8) inches in height and which have gone to seed, but may not include any noxious weeds or nuisance or invasive plants, and must be maintained so as to not include unintended vegetation. (c)Managed natural landscapes may not include any noxious weeds, nuisance or invasive plants, or any other plantings, which due to location and manner of growth, constitute a hazard to the public or may cause injury or damage to persons or property.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 85 | Traffic: Supplement 80).
Full Breakdown
005, where an "invasive plant" is "a vegetation species that grows aggressively in the State of Missouri, as listed by the Missouri Department of Conservation," a "noxious weed" is "a vegetation species that is listed as a Missouri State Noxious Weed by the United States Department of Agriculture," and a "nuisance plant" covers toxic species such as poison hemlock, poison ivy and ragweed. 010. 115(a), (e) and (f).
Violations & Fines
Violating Chapter 620, including planting or allowing a prohibited invasive, noxious or nuisance species inside an otherwise-permitted natural landscape, carries the same penalty as the county's general Weed Control Code: a fine up to $350 or up to 30 days in the county jail, or both, under Section 620.120. Each separate lot or tract counts as its own offense, and each day the violation continues is a separate offense as well.
Frequently Asked Questions
Can I let part of my yard grow wild in St. Louis County?
How does the county decide which plants count as "invasive"?
What's the penalty for keeping a prohibited invasive species in a landscaped yard?
Does this rule apply everywhere in St. Louis County?
Sources & Official References
Other rules in St. Louis County
Compare St. Louis County to another location·View the Missouri invasive plant rules overview
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