Enter your ZIP to see whether this is legal to plant in your state, and whether it survives your winter.
Cascara buckthorn is rated fire resistant overall, with four regional recommendations and one more cautious field-trial score.
Oregon State, Washington State, and University of Idaho extension services list cascara as fire resistant. FireSmart BC approves it as a fire-resistant plant, King County includes it among fire-resistant landscape plants, and Oregon State’s extension service profiles it for fire-resistant landscaping. These recommendations cover British Columbia, western Washington, and the Pacific Northwest.
Idaho Firewise provides the caution. Its field trial gives cascara a fire-resistance score of 7 of 10 on a scale tied to minimum planting distance. Under Colorado State University’s published thresholds for that scale, scores from 4 through 7 are mixed, while recommendations begin at 8. The score therefore falls short of that source’s recommendation threshold, but it does not overturn the agreement among the four regional recommendations.
Cascara buckthorn is a tree in the Rhamnaceae family, reaches about 35 feet at maturity, and needs moderate water. It is native in the southwestern and northwestern United States and grows in USDA zones 3a through 8b. Taken together, the findings support using cascara as a fire-resistant landscape plant while keeping the more guarded field-trial result in view.
Form
tree
Mature height
~35 ft
Water need
moderate
Rated in
British Columbia; OR/WA/ID; Pacific Northwest (Oregon / Washington / Idaho); southern Idaho / Intermountain +1
On this lot
1. Fire evidence and conditions
Fire evidence
Fire-resistant — location does not change the cited classification.
Southern Idaho (ID footprint); partial normalized coverage · 2013-11-08
The official database labels itself "For Southern Idaho" and describes Idaho residents at the urban-rangeland interface. FireApproved publishes 419 existing plant owners that cite its scored rows. This bounded Southern Idaho scope is regional context, not statewide coverage or a conclusion that the score transfers unchanged to every Idaho site.
King County's current wildfire page links this list for the Puget Sound Basin. FireApproved publishes 82 exact source owners as basin context, not statewide Washington guidance or a site-specific recommendation.
The October 2023 joint Pacific Northwest Extension publication explicitly names Oregon, Washington, and Idaho and publishes more than 150 plant profiles. FireApproved has normalized 155 exact plant records from the source; publication scope does not assert that every listed plant suits every site within the three states.
2. Why this plant is relevant here
State distribution
Documented in CA, ID, MT, OR, WA.
Native range
Current cited native range in CA, ID, MT, OR, WA.
Introduced / established
USDA hardiness
2 applicable cited hardiness statements overlap but have different boundaries; compare each complete source row.
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.
Native and introduced range evidence
These are exact U.S. botanical-area records from the cited range source. Native and
introduced describe biogeographic relationship, not fire performance or planting approval.
Doubtful and extinct rows stay visible but do not count as current presence.
The lossless worldwide derivative is retained once in the research corpus; object pages repeat only exact U.S. areas needed by the local lens. The JSON twin carries the same page assertions.
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.
Source location: PlantCharacteristics record 87260, Temperature, Minimum (°F).
Where its sources say to plant it
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 Resistance of Plants Master Database: plantable at 40' from home [Idaho minimum planting distance] (mid-scale rating)
FireSmart BC Plant Program: suitable for HIZ extended zone (30-100 m) [FireSmart BC Home Ignition Zone] (with its recommendation)
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.
