Asters and Goldenrods Primer

Leaf Characteristics

Return to Primer Index

The leaves of asters and goldenrods are often overlooked when people photograph these plants, though the leaves possess many characteristics that are diagnostic.  We can look at their size, shape, margins (edges), petioles and surface traits.

Leaves can be difficult to classify, however, because they are highly variable in certain ways.  The size and shape of a species' leaves not only vary somewhat between individuals of the same species, but even on an individual plant.   Basal, lower-stem (proximal), mid-stem, upper-stem (distal) and branch leaves may all look somewhat different.  For example, let's consider the leaves of a "typical" Symphyotrichum undulatum.  In the image below, the larger leaves on the left are lower-stem leaves, and the leaves on the right are upper-stem leaves.  The image shows the progression from a leaf that is cordate (heart-shaped) and long-stalked, to one that is ovate (egg-shaped), and without a stalk (petiole).

Fortunately, not all species of aster or goldenrod exhibit this much leaf variability.  However, there is usually a size difference between proximal and distal leaves.  For most species, the lower-stem leaves are the largest, and the upper-stem and branch leaves are the smallest.  A noteworthy exception to this can be seen in Oclemena acuminata, for which the mid-stem leaves are the largest.  It is also common for basal and lower-stem leaves to be petiolate, while upper-stem and branch leaves are sessile.

(For surface traits, please refer to the primer discussion in the page on stem characteristics,
for the same traits apply here too.)

Leaf Shapes

The basic leaf shapes are:   cordate (heart-shaped), ovate (egg-shaped), elliptic (ellipse-shaped), lanceolate (lance-shaped), linear (needle-like, extremely thin), spatulate (spoon-shaped).  There are two other common leaf shapes, which are opposites of ovate and lanceolate:  obovate and oblanceolateDetermination of leaf shape defaults to the base of the leaf, rather than the tip.  So, "ovate" means that the broadest part of the leaf is closest to the base of the leaf.  "Obovate" means that the broadest part of the leaf is from the middle of the leaf towards the tip.  Similarly, with "lanceolate" and "oblanceolate".
Cordate
(Eurybia macrophylla & E. divaricata)

Elliptic
(Solidago speciosa)

Spatulate
(Eurybia spectabilis)
Linear
(Ionactis linariifolius)
Ovate
(Solidago flexicaulis)
Obovate
(Oclemena acuminata)
Lanceolate
(Symphyotrichum novae-angliae)
Oblanceolate
(Solidago puberula)

Leaf Margins (edges)

This topic applies to phyllaries and bracts as well as stem and branch leaves.  The basic characteristics of leaf margins include:  serrate (with forward-pointing, sharp teeth), crenate (with rounded teeth or obscure teeth), entire (with no teeth), mucronate (having abrupt, spine-like points), and ciliate (having minute, thin hairs - not teeth).

Serrate (top)
Crenate (bottom)

Entire

  
Mucronate Ciliate

Leaf Tips

The tips of leaves may also help in identifying a species.  The following characteristics apply to leaves, bracts and phyllariesobtuse, acute, acuminate, attenuate, mucronate, spinulose.  Please refer to the definitions and examples in the illustrated Glossary.

Ways Leaves Attach to Stems

There are numerous ways in which leaves can attach to a stem or branch.  We will discuss this a step at a time.  A leaf may have a petiole or leaf stalk or it may not.  If so, the leaf is said to be "petiolate".  If not, the leaf is said to be "sessile".
Sessile Petiolate

A leaf stalk may be simple, or it may be winged.  In the example of a petiolate leaf above, the petiole is said to be "simple".  In the examples below, the petioles are said to be "winged".  The leaf blade may taper abruptly to a short, winged petiole (left), or gradually to a long, winged petiole (right).

To make things even more interesting, leaves may attach to a stem by "clasping" the stem; that is, partially surrounding the stem.  Clasping may be "auriculate", as in the left example, or "cordate", as in the middle example, or "sheathing", as in the right example.

All photographic images and descriptions in this guide are the copyright of Arieh Tal, 2008-2009.  All rights reserved.  You may print an archival copy of these pages for your own use, as for example, to use when conducting field observations.  However, you may not legally sell or otherwise distribute this material without prior permission from the author/ photographer.  Please respect copyrights.

 

 

 

 

 

 

 

 

 

 

 

 

 

01/19/2009