''Asclepias angustifolia'', commonly called the Arizona milkweed , is an

endemic species Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

milkweed ''Asclepias'' is a genus of herbaceous, perennial, flowering plants known as milkweeds, named for their latex, a milky substance containing cardiac glycosides termed cardenolides, exuded where cells are damaged. Most species are toxic to humans ...

native only to

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

.Pollinator Plants of the Desert Southwest, Native Milkweeds , https://www.nrcs.usda.gov/Internet/FSE_PLANTMATERIALS/publications/azpmctn12744.pdf

Description

The Arizona milkweed is a cold-hardy herbaceous perennial that forms a taproot, growing to in height. The stems arise from a single crown, and can be many. Leaves - opposite, linear with short petioles, glabrous, in length, in width; Inflorescence - , erect umbel, single peduncle per node, with one or more peduncles per stem, typically borne towards the top of the stem; Flowers - in diameter and in length, pedicels , horns extend beyond the hoods, corollas reflexed, flower color ranges from whitish to pink; Pods - slender, upright, long, containing few to many seeds; Seeds - ca. 4mm in length, attached to white silky coma in length.

Ecology

Found at higher elevations (around ), it is known only from Pima, Santa Cruz, and Cochise counties in Arizona, United States. Native substrate mostly consists of dry rocky soils. Habit includes riparian woodlands, floodplain meadows, cienega edges, canyons, and arroyo bottoms. It is considered rare in Arizona, and restricted to the borderlands. This species is a known host plant to the

Monarch Butterfly The monarch butterfly or simply monarch (''Danaus plexippus'') is a milkweed butterfly (subfamily Danainae) in the family Nymphalidae. Other common names, depending on region, include milkweed, common tiger, wanderer, and black-veined brown. It ...

. Because it serves as a nesting ground for the Monarch's larvae, it is a vital component in preventing the extinction of these butterflies. It has been observed to be pollinated by small species of Carpenter Bees (''

Ceratina The cosmopolitan bee genus ''Ceratina'', often referred to as small carpenter bees, is the sole lineage of the tribe Ceratinini, and is not closely related to the more familiar carpenter bees. The genus presently contains over 300 species in 23 ...

sp.'').Personal observations made by Pat Mahon - Pure Air Natives, St. Louis, MO - pat@pureairnatives.com

Cultivation

The Arizona milkweed is commercially available by both seed and propagated plants. Seed readily germinates, and mature flowering plants can be grown in as little as three months. Plants can be successfully grown in containers as small as a quart. This species is tolerant of excess watering and lack of watering, in which substrate has not been seen to be an important factor in growth. Substrates utilized have been both organic-rich and replacement to sandy loam profiles. Cold hardiness has been noted to .

Pollination

Asclepias angustifolia pollination is preformed mechanically by insects.

References

{{Taxonbar, from=Q18078765 angustifolia Flora of Arizona