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Asclepias subverticillata - horsetail milkweed

Scientific Family
Asclepiadaceae
Synonyms
Asclepias galioides
Other common names
poison milkweed
Plant type
Forbs and Subshrubs
Origin
Native
Lifecycle
Perennial
Height
6 inches to 4 feet
Riparian
No

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.

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.

Habitat

Grasslands and montane; among grasses, sandy or rocky flats, slopes, roadsides, along trails.

Plant Community
Disturbed Areas
Grasslands
Interior Chaparral
Montane Conifer Forest
Pinyon Juniper Woodlands
Low elevation
2500
High elevation
8000

Flower Characteristics

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.

Flower color
White to greenish-white
Flower shape
Regular
Tubular
No
First bloom month
May
Last bloom month
September
Flower clusters
Rounded

Leaf and Stem Characteristics

Thread-like leaves, 5 inches long, with rolled edges; leaves in whorls of 3 to 5 at stem joints.

Leaf type
Simple
Leaf color
Dark green
Leaf shape
Narrow
Leaf margin
Smooth
Leaf attachment
Whorl
Leaves clasp
No
Leaf hairs
None
Spines
No

Fruit and Seed Characteristics

Erect, slender flattened pod, 4 inches long.

Fruit type
Pod
Fruit color
Brown

Each flat brown seed has a tuft of silky hairs.