Tree and Plant List

The City of Boulder has adopted the Approved Tree and Plant List which goes into effect March 7, 2026. To meet the city's water conservation and wildfire resiliency goals, new trees and plants must be selected from and meet the minimum size requirements within the approved tree and plant list. Alternative plants that are not within the list are permitted if approved by the city after finding the plants consistent with city goals as specified within the Landscape Manual.

Plantings on properties will be reviewed against the list as part of any required landscape plan included with permits for construction but the city urges residents to follow the list even outside the permitting process to comply with state laws on turf use, conserve water, and to ensure the safety of the community and properties from the growing threat of wildfire.

If a landscape plan is required for your property as part of permit or application, please consult the city's Landscape Manual and landscaping regulations in Section 9-9-12, "Landscape and Screening Standards," B.R.C. 1981 within the Boulder Revised Code. If your property is within the Wildland Urban Interface (WUI), please consult the city's Wildland Code in Chapter 10-8.5, "Wildland Code," B.R.C. 1981.

• Perennials – list of hardy, broad-leaved, herbaceous plants that live more than 2 years in the Boulder area
• Shrubs – list of multi-stemmed woody plant species; some species can also be grown as trees and are also
  included on the tree list
• Grasses – list of grass species hardy in Boulder area, including species selected for erosion control, groundcover, and ornamental uses
• Prohibited plants – list of plants not allowed to be included in new developed landscapes, because of their invasiveness, fire risk or, for trees, likelihood of failure in high winds
• Trees – list of trees approved by City of Boulder Forestry Department

• Permitted in Regulated WUI HIZ 5-30 ft – The species marked Y in this column have been documented as having Fire Resistance Scores of 7 or above. These species have documented fire resistance scores of 7 or above and are appropriate for landscapes beyond 5 feet surrounding homes in the designated WUI areas. Please note that these species may vary in fire resistance according to how they are irrigated and maintained.
• Designated wetland – The species marked as Y in this column are native to Boulder County and are also appropriate to use in natural or constructed wetlands and riparian areas.
• Boulder County Native – The species marked as Y in this column have been documented by Boulder OSMP as indigenous to Boulder County. These species should be prioritized in properties adjacent to natural areas.

Use only plants that are from a northern seed source and have been grown in nurseries located in hardiness Zones 1 through 5, as shown on a United States Department of Agriculture map, for at least two full growing seasons for trees and larger woody plants, and the entire nursery cycle for herbaceous perennials and grasses.

Exposure

• Full sun - 6 or more hours of direct sunlight per day
• Part sun - 4 to 6 hours of direct sunlight per day, including afternoon sunlight
• Part shade - 4 to 6 hours of sun exposure per day, with most of that in the morning
• Shade - Less than 4 hours of sun exposure per day, usually in morning or late afternoon or in dappled sunlight under trees

Water Needs and Irrigation

The city plant list includes a water needs category for each plant, that reflects the range of irrigation requirements that the plant will thrive in. The lowest value indicates the lowest amount of water the plant needs to thrive. Each of the values in the list, Very Low, Low, Medium, High, and Cool Season Turf Grass, corresponds to a Plant Factor for use in irrigation design.

A Plant Factor represents the relative water demand of the plant when compared to a reference crop of alfalfa. For example, alfalfa has a plant factor of 1.0, whereas Kentucky bluegrass has a plant factor of 0.9, and Desert Four O'Clock (Mirabilis multiflora) has a plant factor of 0.1. The lower the plant factor, the less water the plant requires.

Many factors are considered when determining the appropriate planting size for a perennial, shrub, or grass. Smaller planting sizes cost less and often transplant more easily. Larger planting sizes may achieve the intended aesthetic effect more quickly and successfully compete with weeds. The listed plant sizes are the smallest planting sizes that will promote design objectives within the first or second year of establishment.

• Download Tree and Plant List (Excel)