Learning the Asters
Asters can be challenging to learn. However, once you become familiar with the
key identifying features of each species, they don't seem quite as hard to
learn. I got a real kick-start learning Asters in the fall of 2004, during a Hamilton
Naturalists Club walk with Dr. Jim Pringle of the Royal Botanical Gardens
(Burlington, Ontario). There's no substitute for an expert identifying and
pointing out the characteristics of each species. This is the best way to learn
One important thing to remember when dealing with Asters is that their common
names vary widely, with even the same common name being used for different
species! So you would be well advised to learn the scientific names of Asters as
Please also see the following...
One tip I will give right now to those who are trying to learn Asters of Ontario. Do not use the Peterson's or Newcombe's field guides to try
to learn these species! You will only end up very confused. Only a portion of
the species featured in these guides actually occur in Ontario. See the
Booklist page for recommended books
about Asters in Ontario.
#1. Here is a list of the common Asters that occur
in Ontario. This is a beginner's list. Get to know all of the species on this
list before moving on to list#2.
#2. These are less common Asters in Ontario. You
might tackle these as "step two" of learning Asters.
#3. Here is a list of Aster species listed in the
Peterson & Newcombe field guides which do NOT occur in Ontario, or are RARE or
VERY RARE in Ontario. In other words, don't bother with these.
- Annual Salt-marsh Aster (Aster subulatus) - rare
- Aromatic Aster (Aster oblongifolius) - not in Ontario
- Bushy Aster (Aster dumosus) - rare
- Cornel-leaved Aster (Aster infirmus) - not in Ontario
- Crooked-stem Aster (Aster prenanthoides) - rare and threatened
- Eastern Silvery Aster (Aster concolor) - not in Ontario
- Late Purple or Spreading Aster (Aster patens) - not in Ontario
- Lowrie's Aster (Aster lowrieanus) - not in Ontario
- Narrow-leaved White-topped Aster (Seriocarpus linifolius) - not in Ontario
- Arrow-leaved Aster (Symphyotrichum urophyllum) - very rare - found mainly east of Ontario
- Perennial Salt-marsh Aster (Aster tenuifolius) - not in Ontario
- Prairie Aster (Aster turbinellus) - not in Ontario
- Rough-leaved Aster (Aster radula) - very rare - found only on James Bay
- Schreber's Aster (Aster schreberi) - rare and threatened
- Short's Aster (Aster shortii) - only found in extreme SW Ontario
- Showy Aster (Aster spectabilis) - not in Ontario
- Small White Aster (Aster vimineus) - not in Ontario
- Southern Aster (Aster hemisphericus) - not in Ontario
- Stiff Aster (Aster linariifolius) - not in Ontario
- Toothed White-topped Aster (Seriocarpus asteroides) - not in Ontario
- Tradescant's Aster (Aster tradescanti) - not in Ontario
- Wavy-leaved Aster (Aster undulatus) - status in Ontario uncertain
- Western Silvery Aster (Aster sericeus) - rare and endangered - only found in the extreme NW corner of the province
- White Wood Aster (Aster divaricatus) - rare and threatened
- Willow Aster (Aster praealtus) - rare and threatened
Introduction to Aster Identification
Asters bloom in the late summer or fall. They have composite flowers, which
means the flowers are composed of Ray flowers and Disc flowers. To the untrained
eye, the Ray flowers appear to be "petals", whereas the Disc flowers appear to
the the actual flower. This is, however, incorrect, The Ray flowers are actually
flowers as well. The two flower types are shown in the following photo
(New England Aster (Symphyotrichum novae-angliae)).
Many aster species have disc flowers that start out yellow, and gradually turn
purple or brown as the flower ages. You will often find flowers with discs of both colours on the same plant.
Asters can be challenging to identify. However, careful observation of their
various key features will help you. When you are trying to identify an Aster,
take note of the following features:
- individual flowers: colour of ray and disc flowers, size, number of ray
- flower grouping: crowded or sparse, flat-topped or rounded, flowers
along the stems or in their own distinct flower head
- leaves: clasping the stem or not, size and shape, fuzzy or smooth. Note
the differences between the basal leaves (at the bottom of the plant near
the ground), middle stem leaves, and upper stem leaves.
- stem: fuzzy or smooth, straight or zig-zag, colour
- branches: upright or spreading out (horizontal)
- overall plant: height, overall appearance
- habitat: field, forest, or wetland
Asters can be confusing and challenging to identify because many of their
features vary from plant to plant of the same species. For example, the stem of
one specimen may be hairy, that of another smooth, yet they are the same
species. Flower colours also vary, as does stem colour (as in
Purple-stemmed Aster (Symphyotrichum puniceum)).
|What makes an Aster an Aster?|
by Dr. Jim Pringle
The following character-states characterize Aster
as traditionally circumscribed (i.e., including plants treated as
Sericocarpus, Biotia, Doellingeria, and Orthomeris by some taxonomists on
the basis of molecular data):
- The flower-heads comprise central disc flowers and peripheral ray
- There are no pales (bracts at the base of the individual flowers) on
the receptacle, nor is the receptacle deeply pitted.
- The involucre comprises small (not foliose) bracts, which are
multiseriate and imbricate (as contrasted, e.g. with those of Senecio,
which are in one short and one long series).
- The ray flowers are pistillate only. The corolla is white, various
shades of pink to purple, or purplish blue, but not yellow. (Plants
formerly called Aster lutescens are now placed in Solidago.)
- The disc flowers are bisexual. The lower part of the corolla is a
slender tube. The upper part flares abruptly and is radially five-lobed.
- The stamens each have a triangular appendage at the apex, but no
appendages at the base of the pollen sacs.
- The stigma comprises two slender branches, with the receptive zones
along the edges. Each branch ends in a triangular appendage that bears
the collecting projections on its abaxial surface.
- The pappus comprises numerous slender, flexible bristles, which are
minutely barbed but not plumose (i.e., they're not branched like a
- The cauline leaves are alternate.