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Asclepias asperula

(Dcne.) Woods.

Spider Milkweed

G5Secure Found in 116 roadless areas NatureServe Explorer →
G5SecureGlobal Rank
UnknownThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.142628
Element CodePDASC02050
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
Endemicoccurs (regularly, as a native taxon) in multiple nations
KingdomPlantae
PhylumAnthophyta
ClassDicotyledoneae
OrderGentianales
FamilyApocynaceae
GenusAsclepias
Other Common Names
spider milkweed (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 Date2025-03-12
Change Date1988-08-01
Edition Date2025-03-11
Edition AuthorsN. Ventrella (2025)
Threat ImpactUnknown
Range Extent200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Number of Occurrences> 300
Rank Reasons
Asclepias asperula is a perennial milkweed occurring in a variety of habitat types, including prairies, woodlands, riparian, shrublands, and desert scrub in North America, from Idaho and Nebraska south to California and Texas in the United States, and south to Oaxaca, Mexico. There are over 2,000 estimated occurrences of this species, which are potentially threatened by development, rights-of-way maintenance, invasive species, and other threats in some places. Little is known about threats and trends, but with a large range extent, high number of occurrences, abundant habitat, broad habitat preferences, and no obvious intrinsic vulnerabilities, Asclepias asperula is considered secure.
Range Extent Comments
Asclepias asperula occurs in North America, from Idaho and Nebraska south to California and Texas in the United States, and south to Oaxaca, Mexico (FNA 2023). Range extent was estimated using herbarium specimens and photo-based observations documented between 1994 and 2025 (RARECAT 2024, GBIF 2025, iNaturalist 2025, SEINet 2025). See individual entries for distribution details about the two subspecies.
Occurrences Comments
By applying a 1 km separation distance to herbarium records and photo-based observations documented between 1994 and 2025, there are estimated to be over 2,000 occurrences rangewide (RARECAT 2024, GBIF 2025, iNaturalist 2025, SEINet 2025).
Threat Impact Comments
Although threats are not widely documented, this species is potentially threatened by development, rights-of-way maintenance, invasive species, and other threats in some places. However, their overall impact is unknown.
Ecology & Habitat

Habitat

Asclepias asperula occurs in a variety of habitats, including hillsides, slopes, mesas, ridge tops, plains, bajadas, canyons, arroyos, streamsides, lakesides, streambanks, dunes, pastures, fields, limestone, shale, sandstone, alluvium, talus, gypsum, igneous substrates, rocky, clay, silt, calcareous, and sandy soils, prairies, shrubby grasslands, oak-juniper, juniper, oak woodlands, pinyon-juniper, oak, juniper, pine, pine-oak, mixed conifer, mesquite woodlands, chaparral, riparian areas, and desert scrub (FNA 2023).

Ecology

This species produces flowers from March through September (–November), and fruits from April to September (–November) (FNA 2023).
Terrestrial Habitats
Forest/WoodlandShrubland/chaparralGrassland/herbaceousDesertSand/dune
Palustrine Habitats
FORESTED WETLANDRiparian
Other Nations (1)
United StatesN5
ProvinceRankNative
KansasSNRYes
IdahoS1Yes
New MexicoSNRYes
TexasSNRYes
ArizonaSNRYes
NebraskaSNRYes
OklahomaSNRYes
UtahSNRYes
NevadaS3Yes
ColoradoS4Yes
CaliforniaSNRYes
Threat Assessments
ThreatScopeSeverityTiming
Unknown/undetermined———

—

Plant Characteristics
DurationPERENNIAL
Economic Value (Genus)Yes
Roadless Areas (116)
Arizona (33)
AreaForestAcres
Arnold MesaPrescott National Forest12,286
Ash CreekPrescott National Forest7,663
Black CanyonPrescott National Forest10,683
BoulderTonto National Forest40,359
Burro CanyonKaibab National Forest19,928
Cherry CreekTonto National Forest11,371
ChiricahuaCoronado National Forest76,876
East Clear CreekCoconino National Forest1,613
GaliuroCoronado National Forest28,333
Grief HillPrescott National Forest12,535
HackberryCoconino National Forest17,885
Happy ValleyCoronado National Forest7,972
Hell HoleApache-Sitgreaves National Forests15,512
HellsgateTonto National Forest6,171
Lime CreekTonto National Forest42,568
Lower RinconCoronado National Forest3,278
Lower San FranciscoApache-Sitgreaves National Forests59,310
MazatzalTonto National Forest16,942
Middle Dragoon RoadlessCoronado National Forest10,543
Mitchell PeakApache-Sitgreaves National Forests35,398
Padre CanyonCoconino National Forest9,431
Painted BluffsApache-Sitgreaves National Forests43,118
PinalenoCoronado National Forest130,920
Pine Mountain Wilderness ContiguousPrescott National Forest3,129
Pine Mountain Wilderness ContiguousTonto National Forest6,518
PipestemApache-Sitgreaves National Forests34,598
Santa RitaCoronado National Forest6,078
Sierra Ancha Wilderness ContiguousTonto National Forest7,787
TumacacoriCoronado National Forest44,594
Upper Rincon RoadlessCoronado National Forest2,991
Walker MountainCoconino National Forest6,382
WhetstoneCoronado National Forest20,728
Willis CanyonKaibab National Forest9,688
Colorado (2)
AreaForestAcres
HermosaSan Juan NF148,103
San MiguelSan Juan NF64,263
Idaho (1)
AreaForestAcres
Bear CreekCaribou-Targhee National Forest118,582
Nevada (4)
AreaForestAcres
Angel Peak NorthHumboldt-Toiyabe National Forest12,577
La Madre - TroutHumboldt-Toiyabe National Forest2,101
Lovell Summit SouthHumboldt-Toiyabe National Forest28,455
PotosiHumboldt-Toiyabe National Forest5,145
New Mexico (37)
AreaForestAcres
Alamo CanyonSanta Fe National Forest8,639
Aspen MountainGila National Forest23,784
Black CanyonSanta Fe National Forest1,922
CajaSanta Fe National Forest5,304
Candian RiverCibola National Forest7,149
Capitan MountainsLincoln National Forest14,069
Chama WS RiverSanta Fe National Forest4,168
Chama WildernessSanta Fe National Forest1,295
Contiguous To Black & Aldo Leopold WildernessGila National Forest111,883
Contiguous To Gila Wilderness & Primitive AreaGila National Forest79,049
Devils CreekGila National Forest89,916
Frisco BoxGila National Forest38,979
Gila BoxGila National Forest23,759
Guaje CanyonSanta Fe National Forest6,104
Hell HoleGila National Forest19,553
Jefferies CanyonLincoln National Forest8,934
Juan de Gabaldon GrantSanta Fe National Forest8,023
Last Chance CanyonLincoln National Forest8,934
Little Dog And Pup CanyonsLincoln National Forest25,412
Little TesuqueSanta Fe National Forest815
Lower San FranciscoGila National Forest26,460
Madre MountainCibola National Forest19,839
Meadow CreekGila National Forest34,167
Mesa AltaSanta Fe National Forest1,868
Nichols ReservoirSanta Fe National Forest1,518
North Rocky CanyonLincoln National Forest8,068
Ortega PeakLincoln National Forest11,545
Peloncillo (NM)Coronado National Forest43,339
Pueblo MesaSanta Fe National Forest3,540
RendijaSanta Fe National Forest2,176
Ryan HillCibola National Forest34,201
Sawyers PeakGila National Forest59,743
South Guadalupe MountainsLincoln National Forest20,930
Thompson PeakSanta Fe National Forest33,001
Virgin CanyonSanta Fe National Forest6,068
West Face Sacramento MountainsLincoln National Forest41,176
YoungsvilleSanta Fe National Forest6,122
South Dakota (1)
AreaForestAcres
Indian CreekBuffalo Gap National Grassland24,666
Texas (1)
AreaForestAcres
Big CreekNational Forests in Texas1,447
Utah (37)
AreaForestAcres
0401002Ashley National Forest36,113
0401024Ashley National Forest12,882
418024Uinta National Forest51,699
418025Uinta National Forest32,698
418026Uinta National Forest14,038
418027Uinta National Forest13,884
Box - Death HollowDixie National Forest3,175
Burch CreekWasatch-Cache National Forest6,938
Capital ReefDixie National Forest763
Cedar BenchDixie National Forest8,915
Clarkston Mtn.Caribou National Forest7,099
CottonwoodDixie National Forest6,754
FishhookDixie National Forest12,959
Hog RanchDixie National Forest17,130
HogsbackWasatch-Cache National Forest7,936
Horse Mountain - Mans PeakManti-Lasal National Forest22,159
Jake HollowDixie National Forest15,146
Lewis PeakWasatch-Cache National Forest11,616
Lone Peak ContiguousWasatch-Cache National Forest874
Long Neck Mesa / Steep Creek / Oak Creek - Steep Creek / OakDixie National Forest55,489
Mahogany RangeWasatch-Cache National Forest11,409
Middle FrancisWasatch-Cache National Forest3,296
Mt. Logan NorthWasatch-Cache National Forest18,930
Mt. Logan SouthWasatch-Cache National Forest17,014
Mt. Logan WestWasatch-Cache National Forest5,285
Mt. NaomiWasatch-Cache National Forest41,922
Mt. OlympusWasatch-Cache National Forest9,982
North FrancisWasatch-Cache National Forest8,148
North PavantFishlake National Forest53,262
Oak CreekFishlake National Forest54,053
PavantFishlake National Forest42,560
Pine Valley MountainsDixie National Forest57,673
Red Canyon SouthDixie National Forest3,736
SanpitchManti-Lasal National Forest29,129
South FrancisWasatch-Cache National Forest3,374
Twin PeaksWasatch-Cache National Forest6,157
WellsvilleWasatch-Cache National Forest1,717
References (7)
  1. 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.
  2. Global Biodiversity Information Facility (GBIF). 2025. Global Biodiversity Information Facility (GBIF) data portal. Online. Available: https://www.gbif.org/ (accessed 2025).
  3. iNaturalist. 2025. Online. Available: https://www.inaturalist.org (accessed 2025).
  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. NatureServe's Rapid Analysis of Rarity and Endangerment Conservation Assessment Tool (RARECAT). 2024. Version: 1.1.1 (released Oct 01, 2024).
  6. Powell, A.M., and R.D. Worthington. 2018. Flowering plants of the Trans-Pecos and adjacent areas. Botanical Research Institute of Texas, Fort Worth, TX. 1464 pp.
  7. Southwest Environmental Information Network (SEINet). 2025. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2025).