Workshop Part 1: Names  Workshop Part 2: Definitions and plant parts   Workshop Part 3: Keys   
Workshop Part 4: Keys
  Workshop Part 5: Weber arnica

Part 6: Keys, D

Below is the entry for Arnica cordifolia from Intermountain Flora.

The full scientific name is 
Arnica cordifolia
Hook. Fl. Boreali-Amer. 1:331. 1834.

Take heart, even experts have trouble identifying plants.  Notice that Rydberg, an expert botanist, named this plant A. pumila in 1900 and A. humilis in 1927.   What might account for such a change?

One species mentioned (A. pumila) is now said to be a "variety" of A. cordifolia, not a full species on its own. 

"What is a species", i.e., when does a plant differ sufficiently from another to warrant species status?

Notice the use of "I" in the last sentence at left.

 The Flora of North America Project was begun in 1982 to produce the most up to date, most complete flora of the United States and Canada. Expected completion date of the 30+ volumes is about 2022.
Plant keys and descriptions in FNA are by the top experts in each genus and family.

Plant keys and descriptions are available free on-line.

Example of use of FNA key, first attempts to name a plant, name changes, and virtual herbaria:

Flora of North America, Pinaceae

Missouri Botanical Garden Picea pungens herbarium specimens:
that Parry collected in 1862 
that Engelmann collected in 1874 

Picea pungens specimen in Utah Valley University Herbarium 

There are a number of other virtual herbaria on-line.


What are some Common Keying Problems and 
What are the Solutions?

1) Jumping to conclusions.  Don't have your mind made up about the identity of a plant before you key it.  Let the key identify the plant.

2) Not understanding terminology.  Use the glossary.

3) Focusing on one, instead of all, characteristics in the couplet.  The first characteristic listed is the most important characteristic, but all characteristics in both parts of the couplet should be examined.

4) Assuming that the maturity of the plant you are keying coincides with the maturity of the plant described in the key. For example, hairs on leaves may be quite prominent when the leaf emerges, longer as the plant matures, and not present later in the season. The key might say, "leaves with woolly hairs". Your mystery plant may not have hairs because it has lost them. Another example: basal leaves are often a diagnostic characteristic but on some plants these, too may not be present at flowering time ("anthesis"). The better the key, the more  such age-varying characteristics are discussed.

5) Keying a plant at one particular stage of its development, usually flowering time, when, in fact, identifying that plant can only be done by observing a number of different characteristics (leaf buds, flower, seed) through the growing season.  (Some plants, Salix, for example, often need to be observed throughout their growing season.  Astragalus are difficult or impossible to identify without the pods.) 

6) Making an incorrect choice at a couplet.  Remember the couplet number where you doubted your choice and restart keying from that couplet.

7) Trying to key a plant that is not in the key.  Use several keys.

8) Trying to key from a photograph or from memory.  Keying in the field is best.  Collect minimally and only necessary pieces of the plant and only if the plant is abundant.

9) Assuming the plant is not found in the county you are searching.  Some keys list the county that the plant is found in, but sometimes this list is only of plants found in a herbarium.  The plant may be in your county but not listed in your key.

10) Assuming that the key is incorrect. Doubt your judgment and use several keys.

11) Assuming that the key is correct.  Keys in a guide book vary in quality.  Use several keys.

The most important guidelines for keying? 
Go slowly, doubt, repeat.



What are the characteristics which help distinguish among the common species below? 
Leaf shape, height of plant, habitat and elevation, flower color, 
leaf color and hairiness, seed (shape, color, size), location, etc.

Senecio atratus
Densely hairy 
(floccose to tomentose)

Erigeron eatonii
Erigeron eatonii
Fine, appressed hairs
Prominent leaf veins.

Mertensia fusiformis
Fine, appressed hairs perpendicular to mid-vein.




Maianthemum and 
Prosartes and


 Cymopterus, Lomatium, Podistera, Oreoxis

Workshop Part 1: Names  Workshop Part 2: Definitions and plant parts  Workshop Part 3: Keys   
Workshop Part 4: Keys
  Workshop Part 5: Weber arnica