The Botrychium genus is a complex group of ferns known to science since the 16th century but only studied in depth and properly sorted into species since the mid-1900s.  In 1938 Clausen recorded just eight species of Botrychium in the United States; by the second decade of the 21st century, Botrychium expert Donald Farrar, had determined that there are over thirty species. (There are only ~35 species world-wide.)  This increase was in large part due to the work (from the 1950s through the end of the 20th century) of Warren and Florence Wagner, the authors of the Botrychium key for the Flora of North America.

The Botrychium life-cycle is fascinating yet still only partially understood.  Botrychiums have only one above-ground portion, one leaf which uniquely is split into two portions, a reproductive branch (the sporophore) and a photosynthetic branch (the trophophore).  Minute spores (produced in grape-like clusters on the sporophore) fall to the ground and are worked into the soil by rain, frost heave, and other natural forces.  The pin-head sized spores spend many years (5-10?) underground, they develop slowly, produce a new plant, and eventually the plant emerges above ground. Buds for several years of growth can be found in the below ground portion of the plant and it is thought that individual plants live above ground for 5-10 years.

Of crucial importance in the life cycle of Botrychiums is their association with mycorrhizal fungi. The fungi are apparently attracted to the below ground spores by secretions of these spores. The fungi attach themselves to the spores and provide the nourishment which the spores need to develop over many years. 

Botrychiums are most often found in disturbed areas, such as, avalanche chutes, rock slide areas, gopher areas, and in elk and deer grazed meadows. They are also found where humans have disturbed areas, such as, road-sides, ski-areas, and logging roads, all of which mimic the naturally disturbed areas that Botrychiums favor.  Botrychiums can be found growing in disturbed areas about 15-20 years after the initial disturbance.

Botrychium are especially sensitive to moisture conditions and/or perhaps it is the mycorrhizal fungi which are sensitive. Whatever is the cause, Botrychium size and timing of appearance vary widely depending on the ground moisture.

Botrychiums in the Four Corners states seem to be most abundant above 9,000 feet. Betty and I have found them as high as 12,600 feet. They are typically in well-drained soils rich in soluble minerals.  They are frequently found where at least two of the following are present: Androsace spp, Antennaria spp, Fragaria spp, Solidago simplex, Senecio atratus, Taraxacum officinale, mosses, lichens, and small Conifers.  They are not found with Vaccinium species or under a closed canopy. 

In sum, Botrychium are found in rocky/gravelly soils in the open spaces between what most of us look at  --  the flowering vascular plants.  One must retrain one's brain so it avoids having you look at flowers three, twelve, or twenty inches above the ground and instead focuses you on the barren gravel and soil between the flowers.

Farrar and Popovich indicate, "While all moonworts can be stubbornly difficult to find, recent field work has shown them to be much more widespread than previously believed. Some moonworts are markedly more prevalent than others and, 95 percent of the time, those encountered in Colorado are Botrychium echo, B. hesperium, B. lanceolatum (red phenotype), B. minganense, and B. neolunaria."

Botrychium species are highly variable and identifying them to the species level is often difficult.  One must deal with mature plants.  According to Farrar and Popovich, "The most important characters for identification are the shape and cutting (dissection) of the pinnae [the individual leaf sections] as well as the lengths of the stalks of the trophophore and sporophore".  It is not necessary to examine the below ground parts of Botrychiums to identify them and, in fact, disturbing these parts should be avoided.  The Wagners indicate that "For accurate identification, a substantial number [of plants must be examined] because of the large amount of variation found in most species".

The Botrychiums of Colorado are the most studied and cataloged plants in the Four Corners states thanks to the work of Steve Popovich and Scotty Smith. (See the key developed by Farrar and Popovich.)

The Botrychium genus was named by Olof Swartz in 1800; he replaced the original genus name of Osmunda given by Linnaeus in 1753.  The name “Botrychium” is derived from the Greek word “botrypus”, meaning “a cluster of grapes” and "ion" a diminutive, thus, "small grape cluster", referring to the cluster of spore-producing sporangia on the sporophore.

The plant is commonly known as "Moonwort", a name that, according to the Oxford English Dictionary, dates back to 1578 in Lyte's book, Dodoeus, a translation of a herbal by Rembert Dodoeus: 

"This herbe is now called in Latine "Lunaria", and "Lunaria minor".  In English "Lunarie" or 'Moonwort' ". 

Leaflets of some Botrychium are crescent-shaped, i.e., lunar-shaped, thus the Latin "Lunarie" and the English "Moonwort".  "Wort" (Middle English) is derived from "wyrt" (Old English) for "a plant".

For more information about Botrychiums:

For photographs, drawings, and complete descriptions of almost all United States Botrychium, see Dr. Donald Farrar's web page on the Ada Hayden Herbarium website.

Click for Donald Farrar's "SYSTEMATICS OF MOONWORTS BOTRYCHIUM SUBGENUS BOTRYCHIUM". 

Click for the Flora of North America key to Botrychium which is another tool to use in identifying Botrychiums but it is superceded by the Farrar and Popovich key.

See also Cindy Johnson's  "Phenology and Demography of Two Species of Botrychium".

Click for Benjamin Dauphin's 2017 PhD dissertation, "Evolution of Moonwort Ferns..." with abundant references, pages 169ff.

Note that the 2012 edition of Weber and Wittmann's Colorado Flora includes the entire excellent illustrated Botrychium key by Farrar and Popovich. Unfortunately editions of Ackerfield's Flora of Colorado do not contain this key and also have range maps that do not give the actual ranges of the species. Click to see the key developed by Farrar and Popovich and see BONAP for accurate range maps.