Linnaeus named this genus (and the tuberosa species) in 1753.  Aesculapius, a legendary Greek physician, was the Greek God of Medicine.  Members of the genus Asclepias have been used medicinally for millennia and are sometimes used in modern herbal teas.

   For diagrams explaining the complex Milkweed flower structure, click and then scroll down to #4. Very interesting.

   Also click to see the ultimate Asclepias page.

   And give one more click to read a very entertaining and scientifically accurate account of Milkweed pollination.

Asclepias involucrata (Dwarf Milkweed)
Apocynaceae (Dogbane Family) formerly Asclepiadaceae (Milkweed Family)

Semi-desert. Sand, canyon washes, shrublands. Spring.
Above and left: Pyramid Trail, Red Rock Canyon, Gallup, New Mexico, May 2, 2015.

Stems of A. involucrata can be up to 10 inches long, but in dry years (such as 2015) plants might be much shorter yet still flower. Plants typically sprawl along the ground in sandy areas at lower elevations (4,000-7,500 feet).

A. involucrata and A. macrosperma (shown below) are very similar and, in fact, a number of floras combine them under the one name of A. involucrata. However, John Kartesz, authority for the nomenclature on this website, separates them into two species, as does the authoritative Flora of the Four Corners Region.

A. involucrata has leaves with no (or very short) petioles, margins that are usually very short hairy below and on the margins which usually are not undulating. Flowers are pale green-white to pale yellow and seeds are less than 8 mm long.

A. macrosperma has leaves with short petioles, abundant hairs, and undulating margins. Flowers are yellow and seeds 10-14 mm.

Charles Wright collected the first specimens of A. involucrata in the 1851-1852 Mexican Boundary Survey and George Engelmann named the plant in Torrey's 1859 description of it. "Involucrata" refers to the swirl of leaves that suggest an involucre below the flowers.

Asclepias macrosperma (Big Seed Milkweed, Eastwood's Milkweed)
Apocynaceae (Dogbane Family) formerly Asclepiadaceae (Milkweed Family)

Semi-desert. Sand, canyon washes, shrublands. Spring, summer.
Above: North of Bluff, Utah, May 6, 2014 and Canyons of the Ancients National Monument, May 3, 2020.
Left: Hunter Canyon, Utah, May 3, 2005.

The soft green of this lovely plant is due to downy hairs that cover the folded, twisted, and wavy-edged leaves, which are ovate lower on the plant and ovate-lanceolate above. Plants sprawl along the ground with large, pale green to light yellow flower clusters emerging from the ends of leaf stems. Flowers are in a starburst sphere typical of plants in the Milkweed Family. Seeds are 10-14 millimeters long, quite larger than those of A. involucrata.

In the photograph immediately above, early morning sunlight transforms Asclepias macrosperma.

See above for the very similar Asclepias involucrata.  

In 1893 Alice Eastwood named and described this species from plants she collected in 1892 along Court House Wash in what is now Arches National Park.  She named it "macrosperma" for its large seeds.

Asclepias macrosperma (Big Seed Milkweed, Eastwood's Milkweed)
Apocynaceae (Dogbane Family) formerly Asclepiadaceae (Milkweed Family)

Semi-desert. Sand, canyon washes, shrublands. Spring, summer.
Hunter Canyon, Utah, May 3, 2005.

This is the same plant as shown in the photograph above, but the leaves shown at left have relatively straight margins making them look similar to the leaves of Asclepias involucrata.

Asclepias tuberosa (Butterfly Milkweed)
Apocynaceae (Dogbane Family) formerly Asclepiadaceae (Milkweed Family)

Semi-desert. Canyon washes, roadsides. Spring, summer.
Above: Road to Needles District of Canyonlands National Park, Utah, July, 25, 2008 and Big Springs Canyon Trail, Needles District of Canyonlands National Park, Utah, September 29, 2017.
Left: Road to Needles District of Canyonlands National Park, Utah, July, 25, 2008.

"Eye-catching", "symmetrical", "orange" sum up this lovely plant.  Asclepias tuberosa is quite common in moist areas of the central and eastern United States, but is uncommon in the west, occurring primarily in the Four Corners states along roadsides and in washes.  The plant is, in the words of Intermountain Flora, "one of the most widely dispersed..., as well as one of the most beautiful, wildflowers of temperate North America....  Asclepias tuberosa is highly variable in habit, foliage, and flower-color."

Linnaeus named this genus (as indicated at the top of this page) and he also named this species in 1753 from collections made in "Habitat in America boreali", i.e., in North America. "Boreali" is Greek for "north". "Tuberosa" refers to swellings on the roots.

Asclepias tuberosa (Butterfly Milkweed)
Apocynaceae (Dogbane Family) formerly Asclepiadaceae (Milkweed Family)

Semi-desert. Canyon washes, roadsides. Spring, summer.
Road to Needles District of Canyonlands National Park, Utah, July, 25, 2008.

Asclepias tuberosa (Butterfly Milkweed)
Apocynaceae (Dogbane Family) formerly Asclepiadaceae (Milkweed Family)

Semi-desert. Canyon washes, roadsides. Spring, summer.
Road to Needles District of Canyonlands National Park, Utah, July, 25, 2008.

Asclepias tuberosa (Butterfly Weed)
Apocynaceae (Dogbane Family) formerly Asclepiadaceae (Milkweed Family)

Semi-desert. Canyon washes, roadsides. Spring, summer.
Big Spring Trail, Canyonlands National Park, Utah, September, 10, 2005.

Ripening seed pods give no indication of the beautiful flowers that have passed.

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Range map for Asclepias involucrata

Range map for Asclepias macrosperma

Range map for Asclepias tuberosa