Roadless Areas
Home/Species/ Stebbins' Madia

Harmonia stebbinsii

(T.W. Nelson & J.P. Nelson) B.G. Baldwin

Stebbins' Madia

G2Imperiled Found in 6 roadless areas NatureServe Explorer →
G2ImperiledGlobal Rank
HighThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.158632
Element CodePDAST650K0
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
Endemicendemic to a single state or province
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderAsterales
FamilyAsteraceae
GenusHarmonia
Synonyms
Madia stebbinsiiT.W. & J.P. Nelson
Other Common Names
Stebbins' Tarweed (EN)
Concept Reference
Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2026-03-16
Change Date1986-10-22
Edition Date2026-03-16
Edition AuthorsD. Gries (1997), rev. A. Treher (2012), rev. Soteropoulos (2026)
Threat ImpactHigh
Range Extent1000-5000 square km (about 400-2000 square miles)
Number of Occurrences6 - 80
Rank Reasons
Harmonia stebbinsii is an annual herb found in open, rocky, habitats with derived from serpentine, including gravelly slopes and barrens within chaparral, lower montane coniferous forest, and wooodland-brush edges. It is endemic to the western United States in the southern Klamath Ranges and Inner North Coast Ranges of California. There are at least sixteen occurrences, which face threats from mining, road construction and maintenance, road bank stabilization with introduced non-native grasses, logging, use of habitat for staging, and fire suppression. Monitoring of populations should be conducted to improve our understanding of reproduction, plant abundance, threats, and trends, as well as continuing conservation measures to protect the taxon.
Range Extent Comments
Harmonia stebbinsii is endemic to the western United States in the southern Klamath Ranges and Inner North Coast Ranges of California, where it has been documented in Lake, Shasta, Tehama, and Trinity counties (FNA 2006, CNPS 2026). Range extent was estimated to be 2611 square kilometers using herbarium specimens and NatureServe Network occurrence data documented between 1994 and 2025 (RARECAT 2025, GBIF 2026, NatureServe 2026, SEINet 2026).
Occurrences Comments
By applying a 1 km separation distance to herbarium specimens and NatureServe Network occurrence data documented between 1994 and 2025, it is estimated that there are sixteen occurrences rangewide (RARECAT 2025, GBIF 2026, NatureServe 2026, SEINet 2026). CNPS (2026) estimates that there are 21 occurrences presumed extant, including five occurrences that have not been observed for over 20 years
Threat Impact Comments
This species faces threats from mining, road construction and maintenance, road bank stabilization with introduced non-native grasses, logging, use of habitat for staging, and fire suppression (CNPS 2026, NatureServe 2026).
Ecology & Habitat

Habitat

Harmonia stebbinsii grows on rocky, shallow, serpentine-derived soils, on gravelly slopes and in barrens with no canopy (<5% cover), in chaparral and lower montane coniferous forest communities as well as woodland-brush edges; it often persists along gravel roadsides constructed through these habitats (Nacamura and Nelson 2001, FNA 2006, CNPS 2026). Associated species include Pinus jeffreyi, P. sabiniana, Arctostaphylos canescens, Ceanothus cuneatus, and Quercus durata.

Reproduction

This species flowers from May to July (FNA 2006). Seed dispersal likely occurs by animals (CNPS 2026).
Terrestrial Habitats
Forest/WoodlandForest - ConiferForest EdgeWoodland - ConiferShrubland/chaparralBarrens
Other Nations (1)
United StatesN2
ProvinceRankNative
CaliforniaS2Yes
Threat Assessments
ThreatScopeSeverityTiming
3 - Energy production & miningSmall (1-10%)Serious or 31-70% pop. declineHigh (continuing)
3.2 - Mining & quarryingSmall (1-10%)Serious or 31-70% pop. declineHigh (continuing)
4 - Transportation & service corridorsLarge (31-70%)Moderate or 11-30% pop. declineHigh (continuing)
4.1 - Roads & railroadsLarge (31-70%)Moderate or 11-30% pop. declineHigh (continuing)
5 - Biological resource useLarge (31-70%)Serious - moderateHigh (continuing)
5.3 - Logging & wood harvestingLarge (31-70%)Serious - moderateHigh (continuing)
6 - Human intrusions & disturbanceRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
6.3 - Work & other activitiesRestricted (11-30%)Moderate or 11-30% pop. declineHigh (continuing)
7 - Natural system modificationsLarge (31-70%)UnknownHigh (continuing)
7.1 - Fire & fire suppressionLarge (31-70%)UnknownHigh (continuing)
7.1.2 - Suppression in fire frequency/intensityLarge (31-70%)UnknownHigh (continuing)

—

Plant Characteristics
DurationANNUAL
Economic Value (Genus)No
Roadless Areas (6)
California (6)
AreaForestAcres
ChinquapinShasta-Trinity National Forest22,040
East ForkShasta-Trinity National Forest6,201
GrindstoneMendocino National Forest26,031
Snow MountainMendocino National Forest14,457
Thomes CreekMendocino National Forest16,616
West BeegumShasta-Trinity National Forest5,198
References (8)
  1. California Native Plant Society (CNPS), Rare Plant Program. 2026. Inventory of Rare and Endangered Plants of California, online edition, v9.5. Online. Available: https://www.rareplants.cnps.org (accessed 2026).
  2. Flora of North America Editorial Committee (FNA). 2006c. Flora of North America north of Mexico. Vol. 21. Magnoliophyta: Asteridae, part 8: Asteraceae, part 3. Oxford Univ. Press, New York. xxii + 616 pp.
  3. Global Biodiversity Information Facility (GBIF). 2026. Global Biodiversity Information Facility (GBIF) data portal. Online. Available: https://www.gbif.org/ (accessed 2026).
  4. Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
  5. Nakamura, G., and J. K. Nelson, eds. 2001. Illustrated field guide to selected rare plants of northern California. University of California Agriculture and Natural Resources publication 3395, Oakland, CA. 370 pp.
  6. NatureServe. 2026. NatureServe Network Biodiversity Location Data. NatureServe, Arlington, Virginia.
  7. <p>NatureServe's Rapid Analysis of Rarity and Endangerment Conservation Assessment Tool (RARECAT). 2025. Version: 2.1.1 (released April 04, 2025).</p>
  8. Southwest Environmental Information Network (SEINet). 2026. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2026).