Enter your ZIP to see whether this is legal to plant in your state, and whether it survives your winter.
Mountain ash is rated fire resistant on limited primary evidence, despite conflicting guidance from U.S.
extension services and a 2023 Greek regulation.
Oregon State University Extension Service profiles Sorbus spp. among fire-resistant plants suited to Willamette Valley growing conditions and prints a hardiness range of USDA zones 3–7. University of Wyoming Extension likewise names mountain ash as an example of a plant for a Firewise landscape. Together, those sources provide practical landscaping guidance for Oregon and Wyoming.
The Hellenic Ministry of Environment and Energy takes the opposite position. Its 2023 fire-protection regulation includes Sorbus sp. in a table of particularly flammable endemic trees and shrubs. The sources differ in purpose and place, but those differences do not establish why their judgments conflict.
Form
tree
Rated in
Greece; Oregon (Willamette Valley); Wyoming
On this lot
1. Fire evidence and conditions
Fire evidence
Fire-resistant — location does not change the cited classification.
Willamette Valley (OR footprint); partial normalized coverage · 2015-02-01
OSU Extension says EM 9103 highlights fire-resistant plants that thrive under Willamette Valley growing conditions. FireApproved publishes 172 exact owners only as valley context. The guide shares the PNW 590 lineage and is not a second independent vote or statewide site clearance.
University of Wyoming Extension published these Firewise examples for its Wyoming rural-living audience and points readers to Firewise Wyoming. FireApproved publishes ten exact source owners while holding broad plant groups. State publication scope is not suitability across every basin.
2. Why this plant is relevant here
State distribution
Documented in OR.
Native range
Introduced / established
USDA hardiness
Documented range 3–7.
3. Legal, ecological, and broader status
Legal-list status
Seed-list status
Reported invasive here
Broader regional context
Federal context
How to read this page
The status above is computed from the cited rows below: independent recommendations can support a fire-resistant result, an avoid row can produce keep-away, and disagreement stays visible as conflict. Placement notes preserve each source’s own scheme rather than translating unlike rules into one scale. This is evidence about a plant, not permission to plant it in every part of the defensible space; Zone 0 remains noncombustible.
Plant hardiness evidence
These values describe the plant source. Your ZIP zone comes from the separate 2023 USDA
Plant Hardiness Zone Map. Whole-zone values stay whole-zone, and a single unresolved value
is not treated as a tolerance range. Different source boundaries stay separate: overlapping
statements are compared independently, while only ranges with no shared zone are called a conflict.
Placement rules below use each source's own distances or named zones, tied to its rating.
They are not interchangeable with the directory's current Zone 0 guidance.
Fire-resistant Landscape Plants for the Willamette Valley: Mountain Ash profile (PDF page 176) [osu-em-9103-profile] (with its recommendation)
Κανονισμός Πυροπροστασίας Ακινήτων εντός ή πλησίον δασικώ…: section 5.4.2, Table 2δi [greece-2023-particularly-flammable] (with its avoid rating)
The evidence
Grouped by what each source concluded. Primary evidence rated the plant itself
(a lab, field program, or original curation); corroboration compiled or
republished another source's rating and resolves to its root lineage.