Several characteristics listed below help to separate A. androsaemifolium and A. cannabinum.  Look at the photographs below to observe these characteristics.  

A. androsaemifolium flower petals are 3-4 times as long as the calyx, about 5/16" long; petals of A. cannabinum are 2-3 times as long as the calyx, about 3/16" long.

A. androsaemifolium flower petal lobes tend to reflex; petal lobes of A. cannabinum tend to be upright or horizontal.

A. androsaemifolium leaves tend to droop and be egg-shaped, about twice as long as wide; leaves of A. cannabinum tend to be horizontal and about three times as long as wide.   

A. androsaemifolium seed pods are about twice the length of its leaves; seed pods of A. cannabinum are more than three times the length of its leaves.

Linnaeus named the Apocynum genus in 1753.  "Apocynum" is Greek for "away dog", i.e., "dogbane".  Extracts of the plant were used as poison to kill wild dogs.

Foothills, montane.  Meadows, moist woods near streams, roadsides.  Spring, summer.
Roaring Fork Road, July 7, 2006.

In 1753 Linnaeus named this species Apocynum fol. androsaemi and in 1762 he renamed it Apocynum androsaemifolium.  In the following 150 years the plant endured dozens of name changes.

"Androsaemifolium" means "with leaves similar to those of the genus Androsaemum", a name once given to the genus that we now call "Hypericum".

Foothills, montane.  Meadows, moist woods near streams, roadsides.  Spring, summer.
Roaring Fork Road, July 7, 2006.

Foothills, montane.  Meadows, moist woods near streams, roadsides.  Spring, summer.
Lower Dolores River Canyon, May 17, 2004.

This is a fairly common but greatly overlooked plant even though it grows up to about two feet tall in thick patches (from underground spreading roots).  It has a very erect and open, airy growth pattern and tiny, but quite elegant white/pink flowers.

Linnaeus named this species in 1753.  "Cannabinum" is Greek for "hemp"; the fiber of mature plants was used for cordage.