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Heart-leaved Aster (Symphyotrichum cordifolium) & Its Relatives

By Arieh Tal, 2016

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Included in these comparisons are several North American "aster" species that have at least some leaves that are "heart-shaped" and borne on petioles.  Because these species share several character states, field identification can sometimes be tricky.  All of these species have leaves that are basally-disposed.  The term basally-disposed refers to a pattern of leaf distribution, in which a plant's largest leaves are the basal leaves, and the mid- to upper-stem leaves become progressively smaller toward the summit of the stem.  More information on the term "basally-disposed" can be found in the glossary entry on this website.

S. cordifolium tends to have more consistently heart-shaped leaves with toothed margins (even those at the middle of the stem) than any of the other species on this list.  S. cordifolium will generally have at least some lower stem leaves present at flowering.  Robust plants may also have persistent basal leaves at flowering.  The general pattern is for stem leaves to become progressively smaller and narrower upwards along the stem.  Stem leaves will also become less "heart-shaped" and less noticeably toothed upwards.  That is, leaf bases will eventually (i.e., for the uppermost leaves) become unlobed, lacking a sinus (notch), and have margins that are untoothed.  In addition, leaf petioles will become progressively shorter and/or wider upwards on the stem.  Eventually the uppermost leaves will have bases that are "wedge-shaped" or very wide-winged petiolate.  This species also often has involucral bracts with green zones that are diamond-shaped, or nearly so.

S. undulatum can best be distinguished from S. cordifolium by its pubescent involucral bracts and leaves that are "wavy" margined (i.e., undulate).  The mid- to upper stem leaves of S. undulatum often lack a heart-shaped base, and are not borne on petioles.  If mid- to upper stem leaves do have petioles, they will be tend to become shorter and wider-winged, though still clasping the stem.

S. urophyllum can be differentiated from S. cordifolium by its long, narrow, slightly spreading involucral bracts with thin green zones (i.e., not diamond-shaped), consistently white rays and mid- to upper stem leaves that lack the characteristic heart-shaped bases.  Some basal and lower stem leaves of S. urophyllum may be present at flowering, and vary from heart-shaped, borne on a narrow-winged petiole, to ovate, tapering to a broader winged petiole, or somewhat truncated at base.

S. lowrieanum has leaves that are more similar to those of S. urophyllum, except that they are often smooth and glaucous (appearing slightly gray-silvery), at least on lower surfaces.  It's stems are often glaucous as well.  Its involucral bracts are well appressed, glabrous and may sometimes have diamond-shaped green zones.

Eurybia divaricata can best be distinguished from S. cordifolium by its flat- to round-topped, corymb-like inflorescence, branch arrays that are also corymb-like, consistently white rays, and bright yellow disc florets.  By comparison, the inflorescence of S. cordifolium is usually panicle-like, peaked or narrowed toward the summit.  Like S. cordifolium, basal leaves of E. divaricata may be deciduous by flowering.  Because its leaves are so similar, it is difficult to distinguish from S. cordifolium until the inflorescence begins to form.

Eurybia macrophylla and E. schreberi are more likely to be confused with E. divaricata, and with each other, than with the Symphyotrichum species.  The three Eurybia species all have corymb-like inflorescences, while the Symphyotrichum species in this grouping all produce panicle-like inflorescences.  Basal leaves are nearly always present at flowering for E. macrophylla and E. schreberi, but infrequently present at flowering for E. divaricata.  The leaves of E. macrophylla and E. schreberi tend to be broader and less conspicuously toothed than the leaves of E. divaricata.  Additional details can be found on species detail pages.

 

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Page updated 2016.02.20