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Rockcress is rated fire resistant, with broad support from extension services, field trials, and FireSmart BC.
Six published assessments recommend Arabis for fire-resistant landscaping, including guidance prepared for the Pacific Northwest, Oregon’s Willamette Valley, British Columbia, Idaho, and Colorado.
The scores add useful detail. Idaho Firewise reports cultivar scores of 7 to 8 out of 10 and bases its favorable verdict on the highest-scored form. On the scale used for that verdict, 8 qualifies as recommended, while 7 falls in the mixed range. Colorado State’s extension service also gives Arabis species an ignitability score of 8 out of 10, meeting its stated threshold for defensible-space zones 1 and 2. That Colorado score draws on Idaho materials, so it reinforces the same result rather than representing a wholly separate trial.
The broader recommendations point in the same direction. Oregon State, Washington State, and the University of Idaho list rockcress as fire resistant; Oregon State also includes it in both its Willamette Valley profiles and its groundcover guidance. FireSmart BC approves it as a fire-resistant plant. Rockcress is a groundcover in the Brassicaceae family, and the Pacific Northwest guide places it in USDA zones 4a through 8b. The overall judgment is favorable, but the 7-to-8 cultivar range makes the particular cultivar worth checking.
Form
groundcover
Rated in
Black Hills, South Dakota; British Columbia; Colorado / Rocky Mountain Front Range; Fremont County, Wyoming +5
On this lot
1. Fire evidence and conditions
Fire evidence
Fire-resistant — location does not change the cited classification.
Black Hills, South Dakota; British Columbia; Colorado / Rocky Mountain Front Range; Fremont County, Wyoming; Maryland, New Jersey, and West Virginia; OR/WA/ID; Oregon (Willamette Valley); Pacific Northwest (Oregon / Washington / Idaho); southern Idaho / Intermountain
Maintenance
Typed publication scope: 9 scopes across 7 cited fire sources
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.
Black Hills (SD footprint); partial normalized coverage
The page explicitly limits itself to the Black Hills, and NFPA Firewise's archived 2006 plant-list index files it under South Dakota. FireApproved publishes 47 exact genus or species owners from 48 printed rows. This is bounded Black Hills context, not statewide South Dakota coverage or a finding that a plant suits a particular site.
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.
Maryland Forest Service says the list contains plants that can be grown in Maryland and identifies Maryland natives. FireApproved publishes 169 exact source owners from the 180 printed rows; an unrepresentable form and duplicate-owner rows are not broadened. The list calls itself non-comprehensive and does not establish suitability for every Maryland site.
NJ; partial normalized coverage
New Jersey DEP publishes a state edition saying the listed plants can be grown in New Jersey and are relatively resistant to fire. Its same 180 printed taxon occurrences map to the 169 conservative owners already normalized for the template family. The list is non-comprehensive and does not establish suitability for every New Jersey site or override the Pinelands Commission's separate placement and fuel-break rules.
WV; partial normalized coverage · 2026-08-26
West Virginia Division of Forestry publishes a state edition saying the listed plants can be grown in West Virginia and are relatively resistant to fire. Its same 180 printed taxon occurrences map to the 169 conservative owners already normalized for the template family. The list is non-comprehensive and provides no comparative or site-specific rating.
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.
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 ID, OR, WA.
Native range
Introduced / established
USDA hardiness
Documented range 4–8.
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.
4–8 explicit range · whole zone precision · source stated
Source taxon: Arabis spp. · exact match.
Source location: Rockcress profile, USDA hardiness zones field.
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)
FireSmart BC Plant Program: suitable for HIZ extended zone (30-100 m) [FireSmart BC Home Ignition Zone] (with its recommendation)
Fire-resistant Landscape Plants for the Willamette Valley: Rockcress profile (PDF page 80) [osu-em-9103-profile] (with its recommendation)
Ignition-Resistant Landscape Plants: suitable for defensible-space zones 1-2 (score 8+) [CSU defensible-space zone] (with its recommendation)
Firewise Landscaping Plants: Herbaceous Annuals and Perennials [Maryland Firewise plant-form tables] (with its recommendation)
Firewise Plant Material for the Black Hills: Flowers & groundcovers [black-hills-plant-form-table] (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.
“Choose the right groundcover plants for your fire-resistant landscape”
· original source
The Rockcress profile prints Arabis species. The gallery points to PNW 590 for complete details.
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 Arabis spp. (rockcress) with the preserved ignitability score.
“Fremont County Firewise Plant List — Arabis sp. — Rockcress”
Listed in the source's Ground Covers section; the page describes its listed Firewise plants as generally low-growing, low-debris, and relatively moist.
Listed as Arabis spp. (Rock Cress). The source says listed species exhibit stronger resistance to ignition by wildfires. Source comments: Many varieties, adaptable to many conditions
