Asters and Goldenrods Primer

Stem Characteristics

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It is useful to examine various characteristics of plant stems when trying to identify a species.  We will look at examples of each of the following characteristics:  stem thickness, surface features, straightness and height.  These features tend to be consistent for individuals of a given species, though there may be some variability in some features due to environmental conditions, such as amount of available moisture or sunlight, or the extent of competition.  Height and thickness are often affected by environmental conditions, whereas surface characteristics and straightness are not.

Stem Thickness:

Individuals of a given species tend to have stems of more or less the same thickness.  Stems tend to be thickest at the base of a plant, and thinner toward the top, though in some cases the differences are minimal.  Stems are either thin or stout.  "Stout" would be applied mostly to plants that are relatively tall and large.  A species that is typically short may have stems that are thick in proportion to the height of the plant, while stems of that same diameter would not be considered thick for a different species which is typically much taller.

This is a good opportunity to introduce two technical terms that occur frequently in field manuals and textbooks:  proximal and distal.  Proximal means "near" or "in the proximity of".  Distal means "far away" or "distant".  Please refer to the glossary entry for these terms for additional details and an example.
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Stems of Eurybia divaricata (left) are considered "thin", whereas stems of Solidago squarrosa (right) are considered "thick" and "stout".  (This trait is difficult to portray photographically.)
      

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Stem Surface Characteristics

There are many technical terms used to describe surface characteristics.  These same terms are applied to leaf, branch, peduncle, bract, phyllary and seeds as well.  Please refer to the Glossary for images and examples. (Or, click links below.)  We mention the most commonly used terms here.

Glabrous:  Smooth.  Lacking hairs.  (No hairs!!)
Glabrate:  Having a few hairs, or scattered hairs.  Almost smooth or glabrous.  (Synonym:  glabrescent)
Glaucous:  Having a waxy, gray-white, grayish, greenish or bluish coating.  (e.g., like that on red or purple grapes)
Pubescent:  A generic term for describing various types of plant hairiness.  Sometimes used more specifically to refer to short, soft hairs.
Puberulent:  Having minute, short hairs; usually also densely so.
Hirsute:  Having coarse, bent or curved hairs.
Hispid:  Having stiff, bristly hairs.
Glandular:  Bearing glands, which are tiny structures, sometimes hairlike, exuding a sticky or oily substance.
Scabrous:  Rough or raspy to the touch, due to the presence of short, stiff hairs.  Sand-papery.

As a general rule, hairiness increases from the proximal end to the distal end of a stem or branch.  Stems that are glabrous proximally, often become glabrate or pubescent distally.  Stems that are glabrate proximally, will usually be more-densely pubescent distally.  Stems that are pubescent proximally, will almost certainly be pubescent distally as well.  In know of no exceptions to this.  There are very few asters or goldenrods that are totally glabrous.  Those that are mostly glabrous have a minimal amount of pubescence distally, even if only on peduncles or near branch leaf axils.
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Stem Straightness

Stems are variously straight or flexuous (bent at the nodes).  "Flexuous", does not mean that a stem curves when it gets longer, or because it was bent around some obstacle, or due to the wind.  It means, strictly "bent at the nodes" (where leaves or branches attach to the stem).  Shown below:  Solidago flexicaulis (left) and Solidago ulmifolia (right).
 
Flexuous                                                    Straight       
In many cases, this characteristic is not exhibited at the proximal end of a stem.  That is, the stem becomes flexuous only distally or above, as where the flowering branches occur.  In other cases, stems are flexuous throughout.
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Stem Height

This trait is heavily influenced by "environmental" factors, such as availability of moisture or sunlight, or the extent of competition.  Nevertheless, some species attain a height of only 2 to 3 feet, whereas others may reach 5 or 6 feet in stature.  For example, Solidago juncea and Solidago nemoralis possess some similarities.  They both may have basal and lower stem leaves during flowering, and they both may have tufts of small leaflets in axils of larger leaves or branches.  One should use caution when in dry locations, for a depauperate S. juncea could be confused with a normal-height S. nemoralis.  Check other characteristics, such as stem hairiness or leaf color to distinguish them.  

 

 

 

 

 


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