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Home/Species/ Eastwood's Milkweed

Asclepias eastwoodiana

Barneby

Eastwood's Milkweed

G2Imperiled (G2G3) Found in 5 roadless areas NatureServe Explorer →
G2ImperiledGlobal Rank
UnknownThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.129291
Element CodePDASC022B0
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
Endemicendemic to a single state or province
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderGentianales
FamilyApocynaceae
GenusAsclepias
Concept Reference
Cronquist, A., A.H. Holmgren, N.H. Holmgren, J.L. Reveal, and P.K. Holmgren. 1984. Intermountain Flora: Vascular Plants of the Intermountain West, U.S.A. Vol. 4, Subclass Asteridae (except Asteraceae). New York Botanical Garden, Bronx. 573 pp.
Taxonomic Comments
While historically the taxonomy of the dwarf milkweeds has fluctuated between one and four species, Riser et al. (2019) did comprehensive molecular, genetic, ecological studies and habitat modeling that has led to greater clarity of the taxonomy of this group. Riser et al. (2019) determined that there are in fact 4 distinct species in this group: Asclepias uncialis, A. eastwoodiana, A. sanjuanensis and A. ruthiae. These taxa are geographically separated which aids in their identification at the state level. A. eastwoodiana is endemic to Nevada.
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2025-12-15
Change Date2025-12-15
Edition Date2025-12-15
Edition AuthorsStoner, N. (1993), rev. A. Treher (2014), rev. C. Nordman (2025).
Threat ImpactUnknown
Range Extent20,000-200,000 square km (about 8000-80,000 square miles)
Number of Occurrences21 - 80
Rank Reasons
Eastwood's Milkweed (Asclepias eastwoodiana) is endemic to the Great Basin of Nevada. Based on sites visited between 1995 and 2024, there are about 45 occurrences and a total population size of about 2100 individuals. About one third of the known locations have not been surveyed since before 1995, and are considered historic. The status of plants (continued presence and abundance), threats, and trends are poorly known or unknown. Threats are not well known, but documented threats include trampling by cattle and habitat loss due to mining. Predation by animals including insects, the development of oil and gas infrastructure, road construction and impacts from off road vehicles may also be threats.
Range Extent Comments
Eastwood's Milkweed (Asclepias eastwoodiana) is endemic to the Great Basin of Nevada, its range includes Nye County and nearby parts of Churchill, Esmeralda, Lander, Lincoln, Mineral, and White Pine counties (FNA 2023). Range extent was estimated to be about 44,000 square kilometers, using herbarium specimens, photo-based observations, and NatureServe Network occurrence data collected between 1995 and 2025. The historic range, including occurrences last observed before 1995, is estimated to be about 49,000 square kilometers (GBIF 2025, iNaturalist 2025, NatureServe 2025, RARECAT 2025, SEINet 2025).
Occurrences Comments
By applying a 1 km separation distance to herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1995 and 2025, it is estimated that there are about 45 occurrences rangewide; there are an additional 22 historic occurrences, which were most recently documented prior to 1995 (GBIF 2025, iNaturalist 2025, NatureServe 2025, RARECAT 2025, SEINet 2025).
Threat Impact Comments
The threats to Eastwood's Milkweed (Asclepias eastwoodiana) are not well known. Threats documented include trampling by cattle and habitat loss due to mining. Predation by animals including insects, the development of oil and gas infrastructure, road construction and impacts from off road vehicles may also be threats (NatureServe 2025).
Ecology & Habitat

Habitat

This plant occurs in valleys, in depres­sions, on flats, on slopes, in arroyos, and on dunes. It occurs on calcareous, tuffaceous, and sedimentary substrates such as granite, gravel, and sandy, calcareous, and clay soils, in shrubby grasslands, desert scrub, shrubland, and pinyon-juniper woodlands, it is endemic to valleys in central Nevada at elevations of 1400–2200 m (Cronquist et al. 1984, FNA 2023).

Reproduction

This plant flowers in May and June and fruits in June (FNA 2023).
Terrestrial Habitats
Woodland - ConiferShrubland/chaparralGrassland/herbaceousDesert
Other Nations (1)
United StatesN2
ProvinceRankNative
NevadaS2Yes
Threat Assessments
ThreatScopeSeverityTiming
1 - Residential & commercial developmentSmall (1-10%)UnknownUnknown
2 - Agriculture & aquacultureRestricted (11-30%)UnknownUnknown
2.3 - Livestock farming & ranchingRestricted (11-30%)UnknownUnknown
3 - Energy production & miningSmall (1-10%)UnknownUnknown
3.1 - Oil & gas drillingSmall (1-10%)UnknownUnknown
3.2 - Mining & quarryingSmall (1-10%)UnknownUnknown
4 - Transportation & service corridorsSmall (1-10%)UnknownUnknown
4.1 - Roads & railroadsSmall (1-10%)UnknownUnknown
6 - Human intrusions & disturbanceRestricted (11-30%)UnknownUnknown
6.1 - Recreational activitiesRestricted (11-30%)UnknownUnknown

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Plant Characteristics
DurationPERENNIAL
Economic Value (Genus)Yes
Roadless Areas (5)
Nevada (5)
AreaForestAcres
Bald Mtn.Humboldt-Toiyabe National Forest41,598
Grant - WiregrassHumboldt-Toiyabe National Forest8,541
QuinnHumboldt-Toiyabe National Forest62,459
The Cove 1Humboldt-Toiyabe National Forest2,847
WilhoitesHumboldt-Toiyabe National Forest11,297
References (14)
  1. Borders, B., E. Eldredge, E. Mader, and C. Burns. 2012. Great Basin pollinator plants: native milkweeds (<i>Asclepias</i> spp.) The Xerces Society for Invertebrate Conservation, Portland, OR in collaboration with USDA-NRCS Great Basin Plant Materials Center, Fallon, NV. NVPMC Technical Note No. 56.
  2. Cronquist, A., A.H. Holmgren, N.H. Holmgren, J.L. Reveal, and P.K. Holmgren. 1984. Intermountain Flora: Vascular Plants of the Intermountain West, U.S.A. Vol. 4, Subclass Asteridae (except Asteraceae). New York Botanical Garden, Bronx. 573 pp.
  3. Flora of North America Editorial Committee (FNA). 2023. Flora of North America north of Mexico. Vol. 14. Magnoliophyta: Gentianaceae to Hydroleaceae. Oxford Univ. Press, New York. xxiv + 505 pp.
  4. Global Biodiversity Information Facility (GBIF). 2025. Global Biodiversity Information Facility (GBIF) data portal. Online. Available: https://www.gbif.org/ (accessed 2025).
  5. iNaturalist. 2025. Online. Available: https://www.inaturalist.org (accessed 2025).
  6. Kartesz, J.T. 1988. A flora of Nevada. Ph.D. dissertation. Univ. of Nevada, Reno. 3 volumes. 1729 pp.
  7. Kartesz, J.T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. First edition. In: Kartesz, J.T., and C.A. Meacham. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden, Chapel Hill, N.C.
  8. Kartesz, J. T. 1999. Comments regarding taxa 1-187 [of list supplied by TNC]. Unpublished, Biota of North America Program, North Carolina Botanical Garden, Chapel Hill, N.C., Nov. 25, 1999.
  9. Mozingo, H.N., and M. Williams. 1980. The threatened and endangered plants of Nevada. U.S. Fish and Wildlife Service and Bureau of Land Management, Portland, OR. 268 pp.
  10. NatureServe. 2025. NatureServe Network Biodiversity Location Data. NatureServe, Arlington, Virginia.
  11. <p>NatureServe's Rapid Analysis of Rarity and Endangerment Conservation Assessment Tool (RARECAT). 2025. Version: 2.1.1 (released April 04, 2025).</p>
  12. Riser II, J.P., S.L. Emel, and E.H. Roalson. 2019. Genetics and ecological niche define species boundaries in the dwarf milkweed clade (<i>Asclepias: </i>Asclepiadoideae: Apocynaceae). International Journal of Plant Science 180(2):160-177.
  13. Southwest Environmental Information Network (SEINet). 2025. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2025).
  14. Spahr, R., L. Armstrong, D. Atwood, and M. Rath. 1991. Threatened, endangered, and sensitive species of the Intermountain Region. U.S. Forest Service, Intermountain Region, Ogden, UT.