Yellowstone County, MT Landscaping Rules: Water Restrictions (2026)

Section 27-1208.F applies whenever a property owner or tenant opts to install an in-ground permanent irrigation system as part of required landscaping. The landscape plan itself must identify where the automatic system goes, how it will be maintained, and what it's meant to do, and must delineate every irrigated and sodded area before the county approves it; the irrigation system also has to go in before the plant material does, not after.

Two operational mandates apply once the system is running. First, low-flow irrigation devices, meaning surface drip, subterranean drip, micro-spray, or a combination of these, are required in any narrow or irregularly shaped landscaped area less than eight feet wide in any direction, specifically to stop overspray and runoff in tight spots; a simple hose bib setup is allowed instead only where the landscaped area is under 1,000 square feet and every part of it sits within 100 feet of a hose attachment. Second, every irrigation system must run on a timer scheduled for evening or early-morning hours to cut evaporation loss, and every automatic underground sprinkler system must carry both rain and freeze sensors so it doesn't run during a storm or a hard freeze.

None of this creates a countywide watering-day schedule for existing lawns; it binds only automatic systems installed as part of an approved landscape plan under a zoning compliance permit.