Following are several characteristics that supposedly separate the two: 

1) A. foliaceus phyllaries tend to be broader and longer.  

2) A. foliaceus leaves are 3-20 centimeters long and 8-25 millimeters wide: its middle stem leaves are less than seven times as long as wide. Overall the leaves of this plant tend to be elliptic to lance shaped.  They are generally shorter and wider than A. spathulatus which tends to have linear to lance shaped leaves.

A. spathulatus leaves are 5-15 centimeters long and 3-15 millimeters wide. The middle stem leaves of A. spathulatus are more than seven times as long as wide. 

The above figures for leaf length and width are from the Flora of North America, but Intermountain Flora, and Utah Flora give measurements that differ up to 50 percent! 

3) A. foliaceus basal leaves are usually withered at flowering time; A. spathulatus basal leaves are usually present at flowering time.

   Flower color in both species is highly variable through all shades of blue/purple/pink/white.

   The Flora of North America notes that "Symphyotrichum foliaceum is extremely variable" and "Symphyotrichum spathulatum is a variable species".  The Flora makes no mention of the distinguishing characteristic of the length to width ratio of the middle stem leaves. 

   The name "foliaceus" refers to the foliage-like phyllaries of this species.  "Spathulatus" is Greek for "similar to a broad sword".  But each species is so highly variable in these two characteristics, that neither name really describes the characteristics of the species.

    In 1995 Guy Nesom proposed moving many members of the genus "Aster" (including the two shown on this page) to the genus "Symphyotrichum"; that genus name is now generally accepted.  "Sym phyo trichum" is from the Greek for "with growing hairs" or "with hairs coming together" and is of unknown reference.

Symphyotrichum foliaceum grows from five to twenty-eight inches tall and is commonly found in small colonies that arise from spreading roots. Basal leaves are often withered at flowering time and stem leaves are broad, prominently veined, and reduced in size and number upwards.  Hairs are often in one to few straight lines on the stem below the leaf base.  

Trichomes are hairs and 'symphy" means "coming together".  So "Symphyotrichum" refers to hairs growing together.

A major distinguishing factor between the two Symphyotrichums shown on this page is their phyllaries: S. foliaceus gets its name from its broad and long, leaf-like (foliage-like) outer phyllaries.  Notice that the lower edges of the inner phyllaries are very light green/white.

Symphyotrichum spathulatum grows from four to twenty inches tall and occurs in colonies that arise from strong, spreading roots.  Basal leaves are usually narrow and up to five inches long and stem leaves are progressively shorter and narrower.  Hairs (either upright or arched) are only on the leaf edges.

  

Look carefully at the phyllaries of Symphyotrichum spathulatum and you will notice that they are dark green at the tips and much lighter green, even almost white near the center and bottom.  You can see the white in the lower right bud.  Phyllaries are in several rows and the outer phyllaries are typically shorter, as in these flowers, but may all be about the same length.  

If you compare these phyllaries with those of S. foliaceus (above) you will see that S. spathulatum phyllaries are narrow, variable in length, and the tip is rather small and not sharply pointed; the phyllaries of S. foliaceus are broad, relatively equal in length (outer phyllaries are often even longer that inner ones), and much more gradually tapering, eventually to a finely drawn out tip.

Unfortunately, however, the phyllary characteristics noted in the above two paragraphs are overlapping and highly variable making a distinction between the two species very difficult. 

Linnaeus named this genus in 1753 and John Lindley named this species in 1834 from a specimen collected by John Richardson on the Mackenzie River of Canada.  In 1995 Guy Nesom proposed moving many members of the genus "Aster" to the genus "Symphyotrichum"; that genus name is now generally accepted.  "Spathulatum" means "spatula-shaped".

Range maps © 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 Symphyotrichum foliaceum

Range map for Symphyotrichum spathulatum