Caldwell, ID Invasive Plant Rules: Prohibited Species (2026)

Caldwell folds its prohibited-species list into the landscaping ordinance rather than a stand-alone invasive-plant chapter. Section 10-02-09-3(3) bans any plant material considered poisonous, toxic, or otherwise posing a nuisance citywide, and it separately incorporates the Trees Not Permitted for Rights-of-Way Property Planting list published in the Treasure Valley Tree Selection Guide, barring every species on that list from street plantings and parking lot landscaping. The restriction sits inside a broader species-selection scheme: § 10-02-09-3(2) requires at least seventy-five percent of the trees and shrubs on an approved landscape plan to be rated low water or moderate water demand and drawn from the same Treasure Valley Tree Selection Guide, and any developer wanting to deviate from that list needs Planning and Zoning sign-off first.

The landscaping ordinance itself only kicks in when a project trips specific triggers: new subdivisions and planned unit developments, industrial developments, special use permits, projects touching riparian or wetland or wildlife areas, rezones and annexations, new principal structures or additions exceeding twenty-five percent of gross floor area or 1,000 square feet, a change of use, or a property vacant for more than twelve months, among others. One built-in exception runs the other direction: inside the APO-1 airport overlay zone, the minimum tree-planting requirement itself is waived to avoid attracting wildlife into flight paths, with two additional shrubs substituted for each tree that would otherwise have been required.