# Arizona Milkweed (Asclepias angustifolia) > A slender riparian milkweed of the Arizona sky islands, carrying white flowers in small side umbels along the upper stem. It grows where there is water in a landscape that mostly has none, which is why it is confined to canyon bottoms, cienega edges and shaded streamsides. Source: https://milkweedusa.com/species/arizona-milkweed/ License: CC BY 4.0 (Milkweed USA) ## Summary A slender riparian milkweed of the Arizona sky islands, carrying white flowers in small side umbels along the upper stem. It grows where there is water in a landscape that mostly has none, which is why it is confined to canyon bottoms, cienega edges and shaded streamsides. ## Key facts | Field | Value | | --- | --- | | Scientific name | Asclepias angustifolia Schweigg. | | Genus | Asclepias | | Family | Apocynaceae | | Common names | Arizona Milkweed | | Status | Native | | Height | 8 in–2.3 ft | | Spread | 1 ft–1.7 ft | | Flower color | white, pink | | Bloom period | May to September | | Light | Full sun, Part shade | | Soil moisture | Average, Wet | | USDA zones | 7-10 | | Leaf arrangement | opposite | | Leaf shape | lanceolate | | Sap | Milky latex | | Root system | Deep taproot, resents transplanting | | Seed stratification | 30 days cold-moist | | Monarch value (0-5) | 4 | | Garden value (0-5) | 4 | | Nectar value (0-5) | 3 | | US states recorded | Arizona | ## Identification - Slender erect stems 20 to 70 cm tall, unbranched or with a few shoots from the middle and upper nodes. - Opposite, almost stalkless leaves, linear to narrowly lanceolate, 4 to 12 cm long and only 2 to 11 mm wide, tapering at both ends and hairless on both surfaces. - White flowers, sometimes tinged pink or pale purple, in umbels 2 to 3 cm across borne at the sides of the upper stem rather than at the tip. - Habitat is the giveaway: canyon bottoms, floodplain meadows and cienega edges between about 3,500 and 7,000 feet. ## Ecology A documented monarch and queen host in southeastern Arizona, and one of the few milkweeds available to them in the Madrean canyons. Its riparian habitat concentrates butterflies, so a small stand carries more traffic than its size suggests. ## Growing Grown in butterfly gardens around Tucson and the Huachucas and occasionally offered by Southwest native nurseries. It wants more water than the desert milkweeds: give it a spot that stays damp below the surface, with sun for part of the day and shade for the rest. ## Cautions Standard milkweed cautions. Milky sap, irritating to eyes. ## Questions **Where does Arizona milkweed actually grow?** Only in southeastern Arizona within the United States, in the canyons and cienegas of the sky island ranges. It is far more widespread south of the border, running down through Sonora and Chihuahua into central Mexico, which is why a plant that is rare here is not rare overall. **Is Asclepias angustifolia the same as narrowleaf milkweed?** No, and the names invite the mistake. Narrowleaf milkweed is Asclepias fascicularis, a widespread western species with whorled leaves. Asclepias angustifolia has opposite leaves and in the United States is restricted to southeastern Arizona. An older name, Asclepias angustifolia Elliott, refers to something else entirely and is not this plant. ## References - Plants of the World Online: https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:94096-1 - GBIF: https://www.gbif.org/species/3170306 - iNaturalist: https://www.inaturalist.org/taxa/47908 - Wikipedia: https://en.wikipedia.org/wiki/Asclepias_angustifolia - BONAP county map: https://bonap.net/MapGallery/County/Asclepias%20angustifolia.png - NatureServe: https://explorer.natureserve.org/Search?searchTerm=Asclepias%20angustifolia ## Photographs - Asclepias angustifolia Grimm 2020 (Braderfly, CC BY-SA 4.0): https://commons.wikimedia.org/wiki/File:Asclepias_angustifolia_Grimm_2020.jpg - Asc. angustifolia (Pamahon, CC BY-SA 4.0): https://commons.wikimedia.org/wiki/File:Asc._angustifolia.jpg - A. angustifolia (Pamahon, CC BY-SA 4.0): https://commons.wikimedia.org/wiki/File:A._angustifolia.jpg - A. angustifolia macro (Pamahon, CC BY-SA 4.0): https://commons.wikimedia.org/wiki/File:A._angustifolia_macro.jpg - Arizona Milkweed photographed in Monterrey, Monterrey, NL, MX (Adriana Nelly Correa Sandoval, CC BY 4.0): https://www.inaturalist.org/observations/15119465 - Arizona Milkweed photographed in Avenida Adolfo Ruíz Cortines, Monterrey, NL, MX (Kenzie Anderson-Bell, CC BY 4.0): https://www.inaturalist.org/observations/78170681 - Arizona Milkweed photographed in 49358 Jal., México (Public domain (CC0), CC0): https://www.inaturalist.org/observations/183870082 - Arizona Milkweed photographed in Pénjamo, Gto., México (Oscar Alejandro Morales Juárez, CC BY-SA 4.0): https://www.inaturalist.org/observations/36631402 ## How to cite Milkweed USA. (2026). Arizona Milkweed (Asclepias angustifolia). https://milkweedusa.com/species/arizona-milkweed/