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Smooth white aster is rated fire resistant, though the support is limited and two scores appear to share the same underlying work.
In a southern Idaho field trial, Idaho Firewise rated Aster porteri 8 out of 10 for fire resistance. Idaho's scale links higher scores with shorter minimum planting distances. For defensible-space zones 1 and 2, Colorado State University Extension and the Colorado State Forest Service accept only scores of 8, 9, or 10. Porter aster qualifies with their ignitability score of 8 out of 10.
Those matching scores should not be mistaken for two fully independent trials. Colorado State credits Idaho materials as the basis for its scoring. Fremont County Firewise supplies a separate kind of support by including Porter aster among its Firewise ground covers. It describes plants on that list as generally low-growing, low-debris, and relatively moist, but it offers no comparative rating or adverse category.
Smooth white aster is a perennial in the Asteraceae family. Its 8-of-10 score clears the published recommendation threshold, and the Wyoming listing points the same way. The fair conclusion is that it is fire resistant, with a favorable but relatively narrow foundation behind that judgment.
Form
perennial
Rated in
Colorado / Rocky Mountain Front Range; Fremont County, Wyoming; southern Idaho / Intermountain
On this lot
1. Fire evidence and conditions
Fire evidence
Fire-resistant — location does not change the cited classification.
Colorado State University Extension and the Colorado State Forest Service publish Fact Sheet 6.305 for Colorado's WUI and varied ecosystems. FireApproved exposes all 114 exact source owners at Colorado publication scope while retaining score, elevation, water, and Idaho-carrier lineage. Publication scope is not suitability for every Colorado site or zone.
Fremont County (WY footprint); partial normalized coverage · 2011-02-25
The source identifies itself as the Fremont County Firewise Plant List. FireApproved publishes its 92 exact source owners as Fremont County regional context. No methodology, current county endorsement, statewide Wyoming scope, or site-specific suitability is inferred.
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.
2. Why this plant is relevant here
State distribution
Documented in CO, ID, NM, WY.
Native range
Introduced / established
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 30' from home [Idaho minimum planting distance] (with its recommendation)
Ignition-Resistant Landscape Plants: suitable for defensible-space zones 1-2 (score 8+) [CSU defensible-space 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.
“fire-resistance score 8 of 10”
· score 8 (idaho-0-10)
Ignition-Resistant Landscape Plants (Fact Sheet 6.305) — Colorado State University Extension / Colorado State Forest Service (Wildfire Mitigation Series) · 2025 · original sourcePrimary evidenceField programlineage: idaho-tree resolves to Fire Resistance of Plants Master Database
“ignitability score 8 of 10”
· score 8 (idaho-0-10)
CSU 6.305 table lists Symphyotrichum (f. Aster) porteri (porter aster) with the preserved ignitability score.
“Fremont County Firewise Plant List — Aster porteri — Porter Aster”
Listed in the source's Ground Covers section; the page describes its listed Firewise plants as generally low-growing, low-debris, and relatively moist.
