Plant Image
Granite Mtn - Tr 308 - Sue Smith

Yavapai County Native & Naturalized Plants

Asclepias subverticillata - horsetail milkweed

Synonyms: Asclepias galioides
Other Common Names: poison milkweed
Plant Form: Forb or Subshrub

Family: Asclepiadaceae

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Granite Mtn - Tr 308
Sue Smith
Granite Mtn - Tr 308
Sue Smith
Plant - summer
Willow Dells Tr
Sue Smith
Plant - summer
Granite Mtn - Tr 308
Sue Smith
Seed pods
Commerce Dr, Prescott
Sue Smith
Commerce Dr, Prescott
Sue Smith
Forb Plant Description

Origin: Native   Life Cycle: Perennial
General Desc: Grows in clumps or patches with very narrow leaves in whorls and bearing white, star-like flowers in round clusters. A very abundant plant in Northern Arizona. Queen and Monarch butterfly caterpillars eat the toxic leaves with no ill effect.
Identification notes: Many stemmed, erect perennial; leaves whorled, 3 or more per node, narrow, hairless on both surfaces, margins curved backwards; head-like flower clusters, 5 greenish-white petals with whitish to yellow horn-like appendages (hoods); fruit stems erect.
Height: 6 inches to 4 feet


Habitat Description: Grasslands and montane; among grasses, sandy or rocky flats, slopes, roadsides, along trails.
Plant Communities: Interior Chaparral, Semidesert Grasslands, Pinyon Juniper Woodland, Montane Conifer Forest, Disturbed Areas
Elevation: 2500 - 8000 feet

Flower Characteristics

Color: White to greenish-white     Shape: Regular in round clusters     Tubular: N     Flowering Period: May - Sep
Description: Rounded, 1 to 2 inches wide clusters of 1/2 inch wide white to cream, sometimes greenish-purple flowers; 5-parted flowers include sepals, petals, a crown (corona) arising from the middle of the petals, upright hoods that look like petals and horns.

Leaf and Stem Characteristics

Leaf Color: Dark green     Leaf Type: Simple     Leaf Shape: Narrow     Leaf Margin: Smooth     Leaf Attachment: Whorl     Leaves Clasp: N
Hairs: No     Spines: N
Leaf Description: Thread-like leaves, 5 inches long, with rolled edges; leaves in whorls of 3 to 5 at stem joints.

Fruit and Seed Characteristics

Fruit Color: Brown   
Fruit Type: Pod
Fruit Notes: Erect, slender flattened pod, 4 inches long.
Seed Notes: Each flat brown seed has a tuft of silky hairs.

  Arizona Cooperative Extension
Yavapai County
840 Rodeo Dr #C
Prescott, AZ 86305
(928) 445-6590
Version 8.0  
Last Updated: Feb 16, 2020  
Content Questions/Comments: Email Jeff Schalau  
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