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Oldwoman is generally rated fire resistant, although an Idaho field-trial score keeps that conclusion from being absolute.
Four of the five assessments recommend it. FireSmart BC approves oldwoman as a fire-resistant plant, while Utah State says it can be firewise when properly used and maintained. Montana State lists it among fire-resistant species adapted to Montana. Nevada’s cooperative extension also includes it, but by a different method: its compilation requires favorable treatment from at least two named western sources. These judgments include expert-curated regional plant lists, a broad approval chart, and a multi-source compilation, so their agreement is useful across several western settings.
Idaho Firewise supplies the caution. Its field-trial database gives oldwoman 7 of 10. On that scale, scores are tied to minimum planting distance, and 7 falls in the mixed band rather than the recommended 8-to-10 band. That does not erase the favorable listings, but it argues against treating “fire resistant” as “safe anywhere.” Oldwoman is a perennial in the Asteraceae family; the practical reading is that it is a well-supported fire-resistant choice when properly placed and maintained, with the Idaho score favoring some separation rather than the closest placement.
Form
perennial
Rated in
British Columbia; Montana / Northern Rockies; Nevada / Great Basin; Utah / Intermountain West +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.
The April 2022 MontGuide explicitly presents fire-resistant species adapted to Montana. FireApproved publishes 92 exact plant records from the source while retaining excluded genus, family, and unresolved rows; the guide itself says not every listed species grows in every part of the state.
University of Nevada Cooperative Extension compiled plants suited to Nevada climate zones and reported favorably by at least two upstream firewise lists. FireApproved publishes 126 exact source owners at Nevada publication scope. The source explicitly makes no independent flammability determination, so these rows remain corroborative.
Utah State University Extension states that this fact sheet selects examples for Utah landscapes and that they require proper placement and maintenance. FireApproved publishes 83 exact source owners at Utah publication scope. The table is not a site-specific planting clearance.
2. Why this plant is relevant here
State distribution
Documented in AK, CT, DC, DE, FL, HI, ID, LA, MA, MD, ME, MI, MN, NC, NH, NJ, NY, OH, PA, RI, VA, VT, WA, WI, WV.
Native range
Introduced / established
1 sourced range or established record. This is not an invasive warning.
USDA hardiness
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.
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)
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.
