From low elevation streams to
alpine meadows some form of Willow abounds in the Four Corners region. But many Willows, especially the shrub Willows,
are difficult and very time-consuming to identify. Here is what William Weber has to say about Willows in his Colorado Flora: Western Slope:
Willows are difficult to identify because the important characters are ephemeral. One needs to know young leaves, mature leaves, flowering and fruiting catkins, and stipules. These parts appear, mature, and fall at different times of the year; in order to see them all one must tag a bush or tree and return to it through a season. Twig color and plant height are also important. Most of us do not have enough patience.... Anyone living near Willow stands and in search of a productive hobby would do well to study them. They actually are easy to know if the species are seen in all seasons.
Intermountain Flora states it this way:
The notorious difficulty of identifying specimens of Salix arises from several sources. Staminate flowers, pistillate flowers, fruits, and leaves all provide useful taxonomic characters, but these are frequently not all available at the same time.... Vegetative characters are frequently plastic. Leaves of vigorous young shoots are not only unusually large, but they tend to have disproportionately large stipules. A number of species that usually have entire leaves sometimes have the leaves toothed, and vice versa.... Several species that usually have pubescent ovaries sometimes have the ovaries glabrous.... Finally, the specific limits are frequently blurred by hybridization, sometimes between species that do not appear to be very closely related.
Following are some of the observations one needs to make in order to identify Willows:
1) Does the plant flower before the development of leaves or at the same time?
2) Are the seed capsules glabrous or hairy?
3) What is the leaf color and what is the shape of the leaf and margin?
4) Are the twigs and branchlets glaucous, hairy, glabrous?
5) What is the shape, size, and duration of the stipules?
6) What are the dimensions of the catkins?
Unfortunately, even if one makes notes on the above characteristics, one still should be quite hesitant in ones conclusions about the identity of a particular Willow because, as the quotation above from Intermountain Flora makes painfully obvious, and as the reading of complete descriptions of Willows makes even more painfully obvious, there often is a very wide range of variation in plant characteristics. For instance, leaves of a particular species might be hairless, oval, blunt-tipped, and smooth-margined or hairy, long and narrow, pointed at the tip, and serrated.
I personally find that it is best first to learn those Willows closest to home, i.e., those Willows one sees and can study most often. Then one can pick other Willows which have unusual characteristics, such as the drier land growth habitat preference of Salix scouleriana. One has the best chance of keying species in the spring.
The botanical key that you use to identify Willows can also make quite a difference in your ability to arrive at a satisfying answer. Some botanical keys, such as Weber's Colorado Flora, are all inclusive, i.e., one must look at the Salix species for numerous characteristics at the same time. But if those characteristics are not present when one is attempting to key, one is just not able to identify the plant. Other botanical keys, such as Welsh's A Utah Flora and Cronquist's Intermountain Flora, provide three separate keys: a key to Salix when male flowers are present, a key when female flowers are present, and a key when no flowers are present, i.e. a vegetative key. (Click for a vegetative key.) Multiple keys allow one to key at many different times of the year.
Birds and deer don’t seem to mind the identification
problems; they use Willows for nesting sites and browse the plants without ever knowing
the exact species. Native Americans utilize Willows (and Aromatic Sumac, Rhus
aromatica) in basket making. And, of course, Willows are often planted as ornamentals throughout the Four Corners region, the United States, and in many other parts of the world.
The genus, Salix, was named by Linnaeus in 1753. "Salix" is the classical Latin name for "Willow". |
Species present in state and native
Species present in state and exotic
Species not present in state
Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Eradicated
Questionable presence
