Family:     Apocynaceae (Dogbane family)

Duration:  Perennial

Height:     30-100 cm (1-3 ft)

Blooming: June-July.

Tall Green Milkweed

Asclepias hirtella (Pennell) Woodson

Stems: erect with a single stem rarely branching from the base.  It is usually densely covered with small hairs but can be hairless.  Reddish-green to light green.

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Flowers: small, 5-parted flower.  The inflorescence (or collective flowers) are in an umbels which grow on the upper nodes of the plant.  Each flower are usually a pale green with a tint of purple.  

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Leaves: are long and narrow (linear-lanceolate) with short petioles or subsessile.  The leaves are 7-16 cm long and 0.6-1.5 cm wide.  Pretty rough if you run your fingers along them.  They are what is called, "irregularly approximate" which means the the leaves are usually alternate, but can be opposite.  

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Fruits: are follicles 6-15 cm long.

Sun: full sun

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Habitats: savannas, dry fields, prairies in sandy soil

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Comments: 

Tall milkweed usually has leaves in an alternate arrangement.  Most milkweeds, other than butterflyweed (Asclepias tuberosa), have them oppositely arranged.  Another similar species is green comet milkweed (Asclepias viridiflora).   Neither tall green or green comet milkweed's have horns, tall green milkweed has alternate leaves whereas green comet milkweed usually has opposite leaves. 

Etymology: The genus Asclepias was named by Carl Linnaeus after the Greek god of medicine, Asclepius. The name, hirtella, comes from the Latin word, hirtus, literally meaning "bristly" or "short & stiff hairs" referring to its hairy stem. 

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all photos by  Nathanael Pilla

SOURCES & FURTHER RESOURCES:

Consortium of of Midwest Herbaria - Asclepias hirtella

Flora of Wisconsin - Asclepias hirtella

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Woodson, R.E., 1954. The North American species of Asclepias L. Annals of the Missouri Botanical Garden, 41(1), pp.1-211.