Monthly Fern Finale—Moonworts!

"A very singular and very pretty plant ... [leaflets] are rounded and hollowed, and thence its name came of Moonwort" Sir John Hill, 1770. (image from Atlas der Alenflora 1882).

About 2075 years ago, during the first century BCE, Roman philosopher Cicero wrote of introductions—their importance and how they should be constructed (1):

"one's opening remarks, though they should always be carefully framed and pointed and epigrammatic and suitably expressed, must at the same time be appropriate to the case in hand; for the opening passage contains the first impression ... and this ought to charm and attract the [reader] straight away."

After looking up "epigrammatic" (relating to a short saying or poem that expresses an idea in a clever, funny way), I sat down to construct an introduction "appropriate to the case in hand" — Moonworts.

First the epigram, from Botrychium lunaria by Giles Watson.

Hear the latch click in the gloom,

Thus gain admittance to the room.
By fern and stealth, no guile nor wealth
Can buy a lock to hinder me. 

Now the charm, of which there's no shortage!

After an unknown number of years underground, Botrychium simplex grows a leaf (J. Hollinger).

Moonworts (Botrychium species) are attractive little ferns, and it's unfortunate they're rarely seen. They live mostly underground in the intimate company of Glomus—a fungus that forms mutually beneficial subterranean relationships with nearly 80% of vascular plants. Typically Glomus supplies nutrients to the plant, and the plant supplies Glomus with carbohydrates via photosynthesis. But photosynthesis requires sunlight, so how can a Moonwort make carbohydrates if it lives underground? Maybe it's a parasite rather than a partner. This is just one of Moonworts' mysteries.

When conditions are right (another mystery), or perhaps when the stars align, a Moonwort sends up a single leaf. Though distinctive it's difficult to spot, being small, short-lived, and often hidden in vegetation or duff. But lucky is the finder of a Moonwort! If collected by the light of a full moon, the fertile part can be used to pick locks, unshoe horses, and turn mercury to silver.

Moonwort leaf with a sterile leaflike trophophore and a fertile (magical) sporophore; closeup shows sporangia have opened and released spores (Britton & Brown 1913).

Mingan's Moonwort releasing spores; soon it will wither and be gone (R&N Crawford).

The first known scientific description of Moonwort appeared in 1542, in a revolutionary herbal by physician and botanist Leonhart Fuchs: De Historia Stirpium Commentarii Insignes, Notable Commentaries on the History of Plants. It contained 500 high quality and largely accurate illustrations to help with identification—a novel approach which Fuchs felt obliged to explain: "a picture expresses things more surely and fixes them more deeply in the mind than the bare words of the text."

Lunaria minor, from Fuchs's 1542 herbal. BHL

Leonhart Fuchs c. 1543 (source).

Descriptions in Fuchs's herbal were brief and often "borrowed" from earlier works, an accepted practice. Lunaria minor was said to have a round stem, with a single leaf divided into seven parts and with a stem atop which were seeds (fern reproduction was assumed to involve seeds, though none had been found).

Lunaria minor (the name) and Moonwort seeds would persist for several centuries. Then in 1753, pioneering plant taxonomist Carl Linnaeus put Moonworts in the genus Osmunda (but he too referred to seeds; spores weren't accepted until the mid 1800s). In 1845, Czech botanist Carl Presl moved Moonworts to the genus Botrychium, where they mostly reside today (2), and recognized 17 species. But in the first "modern" treatment of Moonworts, Jens Clausen (1938) reduced this to just six, all of which occurred in both Europe and North America.

We look back on Clausen's classification as much too simplistic. But nearly 50 years would pass before someone took enough interest in North American Moonworts to do something about it—specifically Warren and Florence Wagner, who upped the number to 22. Study and discovery have accelerated since. Currently 38 Moonworts are known for North America (Farrar 2024), with several more species in the pipeline.

A recently-described North American Moonwort—Botrychium farrarii (Legler & Popovich 2024). Note variation.

With so many species and such small plants, Moonwort identification is notoriously difficult (3). Characters are often minute (10x magnification helpful). Differences can be subtle, relative, and variable. No wonder we're regularly referred to experts for confident id. And the experts may resort to molecular techniques (e.g. DNA, enzymes) for verification.

So what are we to do in our South Dakota plant guide, aimed at enthusiasts as well as professionals? We shall follow the advice of Leonhart Fuchs, still sound after all these years. High quality photos will accompany relatively brief descriptions. Discussion of lookalikes will note similar species, offer possibly useful differences, and most likely refer the user to technical manuals and experts.

Fortunately, we do NOT have to identify a Moonwort to species to enjoy it! Just finding one is exciting, and examining it closely can be magical. For example ...

Botrychium matricariifolium was named for its twice-divided trophophores, reminiscent of the leaves of matricary (chamomile). It appears to be rare in South Dakota, found at a few sites in the Black Hills.

Matricary Moonwort is a relatively large moonwort—to 25 cm tall (MWI).

Up close, the trophophore has a lacy elegance (MWI). 

The branched sporophore has many bead-like sporangia, each one containing thousands of spores! (MWI)

Prairie Moonwort, Botrychium campestre, may be our smallest Moonwort. In South Dakota it occurs in grasslands, true to its name. It too appears to be rare, but one never knows with Moonworts! It may be hiding in the grass, or lurking underground for years, waiting for the stars to align.

Prairie Moonwort usually is less than 4 cm tall (NPS).

Botrychium simplex, Least Moonwort, has been found at widely scattered sites, from grasslands and sandhills in eastern South Dakota to a picnic area in the Black Hills. It's both extremely variable and quite similar to at least four other species in the state, making id extra difficult.

Variation in Botrychium simplex—yikes! (compiled from this source).

I'm including the next photo because I loved the comment on the field form—"Not expected out here!" That's a Moonwort for you. They seem to do just fine beyond the limits of "typical habitat". But typical habitat may just be where we typically look for them. Obviously we still have a lot to learn!

Least Moonwort (center) along a seepy creek in sagebrush steppe in Nevada! (mreala)

And so the Monthly Fern series comes to a close. Thank you for reading, happy holidays to all, and best wishes in the year to come!

Notes

(1) In De Oratore, Cicero was actually addressing speaking, but his advice for introductions seems applicable to writing.

(2) Some former Botrychium species are now in separate genera, though not everyone agrees. In South Dakota we have Botrypus virginianus (Rattlesnake Fern) and Sceptridium multifidum (Leathery Grapefern).

(3) In contrast to seed plants and true ferns, where identification relies heavily on reproductive parts (flowers, cones, spore-filled sporangia), Moonwort identification relies almost entirely on the leaf-like trophophore. What it's shape and size? Is it divided? how many times? For leaflets—specifically the lowest pair—determine shape, margins, and how they attach to the midrib. Compare them to those above ... and more.  Small size and variability compound the challenge.

Sources

Farrar, DR, and others? Moonwort Systematics, Ada Hayden Herbarium, Iowa State University. Accessed December 2025. A great resource, with descriptions and photos for many Botrychium species.

Farrar, DR, Gilman, AV, and Moran, RC. 2017. Ophioglossales, in New Manual of Vascular Plants of Northeastern United States and Adjacent Canada. NYBG Press (apparently not yet published—another moonwort mystery).

Farrar, DR, and Johnson, C. 2024. Botrychium subgenus Botrychium: Moonwort biology basics. American Fern Journal 114:10-21. https://doi.org/10.1640/0002-8444-114.1.10

Hill, J. 1770. The useful family herbal: or, An account of all those English plants, which are remarkable for their virtues ...  BHL

Legler, BS, and Popovich, SJ. 2024. Botrychium farrarii (Ophioglossaceae), a new diploid Moonwort species from the Bighorn Mountains of Wyoming, U.S.A. American Fern Journal 114:32–48. PDF

Geohopping across Nevada

Burners at incipient plate boundary in western Nevada. Are they waving California goodbye? (original unknown)

Many times I've crossed Nevada in the company of Frank DeCourten and Norma Biggar (hereafter called D & B). Actually I've never met either one, but I know their Roadside Geology of Nevada well. That's where I learned of the state's traumatic history—torn apart, reassembled, buried in ash and welded rock, and now being torn apart again. These stories can be hard to grasp, but I've read and reread the lengthy introduction enough to be awestruck by landscapes that many travelers find dull.

Sturdily bound, with high quality paper—my copy has survived lots of use.

Maps, diagrams and photos are abundant!

In the eight years since D & B published their book, I've often parked off the highway at their suggestion to study and photograph a geologic feature. I think of this as geohopping to geostops, rather than my usual geotripping to geosights (and later blogging about it). Now it's time to give the geostops their due.

One of my favorite stretches of highway between Laramie, Wyoming (home) and the California Central Coast (home of relatives) is US 6 across Nevada. Traffic is light, towns are few, and the geology truly is dramatic!

Geo highlights along US Highway 6, May 2025.

For example, about thirty million years ago, widespread cataclysmic destruction associated with the Great Ignimbrite Flareup (GIF) created Hell right here on Earth. Supervolcanoes erupted repeatedly across today's Nevada depositing ash thousands of feet deep, much of it welded into rock by the searing heat ("ignimbrite" means "fire cloud rock"). Trying to recreate that terrifying Flareup in my mind is one of the joys of driving across Nevada.

But it's impossible to properly imagine the GIF, in part because "no volcanic eruptions ever witnessed by humans come close to rivaling these prehistoric paroxysms." And the geologic record suggests it may be one of the largest ever. Consider this: in Nevada at least 230 supervolcanoes ejected an estimated 17,000 cubic miles of lava! Here's another way to think about it: at least 30 of these eruptions each equaled 600 Mt. St. Helens eruptions!

Blue Jay Maintenance Station on left, remnants of cataclysmic destruction behind.

About 90 miles southwest of Ely, I stopped at Palisade Mesa in the southern Pancake Range. Parking is available at a small rest area next to the Blue Jay Maintenance Station. Volcanic rocks of the GIF are nicely exposed on the steep slope to the east.

Rock pancakes stacked oldest to youngest, from bottom to top.

Palisade Mesa is one of multiple gently-tilted stacks of volcanic rock that give the Pancake Range its name. The escarpment at Blue Jay shows at least four episodes of eruption, all from the immense Central Nevada caldera complex. The pale bottom (oldest) layer is a lightly-welded tuff from an ash flow c. 31 million years ago. Next is a thin black band of glassy vitrophyre—"a flow of glowing ash that became densely welded."

Vitrophyre—beautiful memento of incandescent destruction. James St. John.

The massive brown layer above the vitrophyre is a younger tuff, about 30 million years old. Being a fan of columnar jointing, it was my favorite. The summit is a 2.75 million-year-old tuff that's sufficiently welded to provide an erosion-resistant cap.

I 💖 columnar jointing—created by contraction with cooling.

The view south beckoned.

Palisade Mesa obviously deserved a longer visit, perhaps a hike along the base and up the valley to the south. But not this time. Instead I continued west.

Those who cross the middle of Nevada (e.g. east to west) soon become aware of its extensive deformation even if they have no idea what happened. For example: When I left the Pancake Range I crossed Hot Creek Valley, then the Hot Creek Range, then Stone Cabin Valley, then the Monitor Range, and then Ralston Valley before stopping in Tonopah near the crest of the San Antonio Mountains. This is typical Nevada topography—valleys and mountain ranges one after another, all trending roughly north–south. The great pioneering geologist Clarence Dutton called them “an army of caterpillars marching north from Mexico".

Left of center, caterpillars are marching across the Basin and Range Province (NPS).

The cause of this curious pattern is east-west continental stretching, which started about 30 to 40 million years ago and continues today. Some parts of Nevada and adjacent Utah and California have nearly doubled in width! In the process normal faulting has dropped basins, leaving adjacent land standing high, as mountain ranges.

In Tonopah, I stopped for gas and groceries as I often do. Here Hwy 6 merges with heavily-traveled Hwy 95, but at Coaldale Junction they diverge, and once again I had the highway mostly to myself. This is where I stumbled upon Radio Goldfield several years ago, broadcasting very local news and interesting country-ish, old-timey, new-to-me music. It's still going strong.

At the advice of D & B, I kept an eye out for a diatomite quarry on the left, near the junction with NV Hwy 264. The white patches were obvious. This diatomite is thought to be the same age as late eruptions of the GIF, but the setting was entirely different—a shallow freshwater lake where diatoms (microalgae) basked in the sun. Now they're diatomaceous earth, a soft crumbly rock that's 80–90% silica. Among its many uses are metal polish, toothpaste, cat litter, dynamite, thermal insulation, and bonsai soil amendments.

I would have enjoyed examining the diatomaceous earth, but wasn't clear on ownership.

Diatomaceous earth up close; scanning electron micrograph by Dawid Siodłak.

After continuing east across Montgomery Pass, I dropped into Queen Valley for the final geostop of the day, parking in a large pullout not far from California. Across the valley was the north end of the White Mountains; the snowy Sierra Nevada was visible in the far distance. It was a lovely peaceful place, or so it seemed that day. But nearby there were clear signs of geologic trauma.

White Mountains rise steeply above floor of Queen Valley.

Normal faulting evidenced by triangular facets (arrows).

Across the valley at the base of the White Mountains is a normal fault just 3 million years old. This is the Queen Valley fault—a tiny piece of the immense Walker Lane. I had entered a profound but vague tectonic boundary, where the Basin and Range Province meets the great Sierra Nevada.

At Walker Lane (yellow), very different tectonic regions meet. SAFZ is San Andreas Fault Zone, a critical part of this story (Carlson et al. 2013).

Walker Lane is young—just 10 million years old at the south end, and only a few million at the north. The combination of Basin and Range extension and transverse movement of the Sierra Nevada has created a complex zone of faults that's poorly understood. Even so, Walker Lane generates a great deal of excitement among geologists. Perhaps a new plate boundary is forming! Maybe California will drift away!

Like the better known San Andreas Fault to the west, Walker Lane is contributing to the slow, incessant, contrary motions of the Pacific and North American tectonic plates, which are pulling a large part of California northward. Currently the San Andreas is responsible for about 80% of this movement but Walker Lane appears to be catching up.

Fauds & Henry (2008) predict that in another 7 to 8 million years or so, the northern part of the San Andreas will join Walker Lane, extending the Gulf of California north by hundreds of miles and turning California into a peninsula along a new plate boundary. 

If this tectonic shifting continues, as the authors think it will, California will become the island that was regularly reported by explorers hundreds of years ago! This was the "famous cartographic error that appeared on many European maps from the 16th to the 18th centuries" (David Rumsey Map Collection).

"Novissima et accuratissima totius Ameriae" by Nicolaes Visscher, 1690. Large island off the west coast of North America is California. DRMC

Peering even further into the future, we may well find that California Island has become an exotic terrane (quit snickering!). As such, it could travel far and wide before being stopped at some convergent plate boundary, thousands of miles from its origin at Walker Lane.

But Emmie ... our ephemeral lives mislead us. The Earth is far from stable.

Sources

agimark 2018. Splitting North America – The Walker Lane; Part 1 – The Tectonics; Volcano Hotspot blog. Accessed Dec 2025.

Carlson, CW, et al. 2013. Kinematics of the west-central Walker Lane ...  Geosphere 9: 1530–1551.

David Rumsey Map Collection, an unbelievably wonderful resource for fans of old maps. WARNING: it's very easy to spend a lot of time here. https://www.davidrumsey.com/

DeCourten, F, and Biggar, N. 2017. Roadside Geology of Nevada. Mountain Press.

Faulds, JE, and Henry, CD. 2008. Tectonic influences on the spatial and temporal evolution of the Walker Lane: An incipient transform fault along the evolving Pacific – North American plate boundary. Nevada Bureau of Mines and Geology, Arizona Geological Society Digest 22. The future of California is discussed on page 463. PDF

Wolterbeek, M. 2020 (Feb 18). How the burgeoning Walker Lane may split the American West; in Nevada Today, UNV Reno.