The Monthly Orchid—an introduction

The pouch-like lips of Fairy Slippers (Calypso bulbosa) are exquisite with their purple patterns and bright yellow hairs. No wonder fairies collect them at night to wear for dancing! (NPS)

Once again, I'm starting a series of posts about South Dakota plants—in part so that I can learn more about the state's flora (I'm still contributing to the online guide). In 2024 I wrote about trees, mostly the less familiar ones from the eastern part of the state. Last year I focused on ferns and fern relatives (lycophytes), and became a pteridomaniac in the process!

This year, after writing descriptions for sedges and rushes, and while starting on grasses, I considered doing a series about graminoids. But after a few weeks of struggling with species differentiated by tiny green structures, I came to my senses and went in a totally different direction—orchids! Their flowers are colorful, sweet-scented, diverse, relatively large, and highly-evolved.

Twenty-seven native orchid species have been reported from South Dakota. Some have large colorful flowers. Others have sweet-scented flowers, or flowers with unusual parts (e.g. threadlike or deeply dissected petals). But most of our species have flowers that aren't showy. They're small and subdued in color—white, greenish, yellowish, or brownish red. But up close they're gorgeous and obviously orchids.

Spotted Coralroot (Corallorhiza maculata); the white lip with purple spots has yellow gobs of pollen hanging over it; lip c. 6 mm long (MWI).

Like almost all orchids (99%), ours have a combination of features unique to the family: a LIP petal (tepal), a COLUMN consisting of the stamen(s) and pistil, POLLINIA made of pollen grains, and minute SEEDS.

Parts of an orchid flower (Serena Aceto).

The LIP or labellum is one of an orchid flower's six tepals (three sepals and three petals). Five of the tepals are more or less alike, but the lip is quite different—in shape, color, size and more. It's also distinctive among species, and is used in identification (fortunately it's easy to see). The lip appears to provide a landing platform for visitors, and species-specific forms are thought to be designed for specific pollinators—the product of coevolution.

Stream Orchid (Epipactis gigantea) has lips with "tongues"; these move when the flower is bumped, hence its other name: "Chatterbox"; flowers to c. 5 cm wide (Dcrjsr).

The lip of Loesel's Twayblade (Liparis loeselii) is showy relative to the other tepals, 2 of which are horizontal and threadlike; flowers to c. 1 cm long (MWI).

Most orchids have a single stamen, which is joined with the pistil to form a COLUMN. Among species, columns differ in size, shape, color and function. In White Lady's-slipper (below), the top of the column presses against the lip, preventing pollinators from leaving the way they came in. Instead they must exit via a narrow slit in the back of the pouch. Inexperienced bees may take up to 15 minutes to find the exit, and may fall prey to crab spiders lurking within! (source)

Small White Lady's-slipper (Cypripedium candidum) has a glossy white inflated lip to 2.5 cm long; yellow flap with red spots is the column tip (MWI).

In most orchids pollen grains are amassed into POLLINIA, bound together by threads of clear sticky viscin. Pollinia are carried off by pollinators to be deposited (hopefully) on stigmas of the same species. The advantages of dispersing pollinia rather than pollen grains will be explained shortly (below).

Ophrys orchid with a pollinator about to get hit with yellow pollinia (ErwinMeier; arrow added).

Finally, orchids produce the tiniest of SEEDS, which number in the thousands or even millions per flower! This means that there are equally numerous ovules in a single pistil. Now we see the advantage of pollinia. Thousands or sometimes millions of pollen grains packed into a pollinium land on a stigma all at once, ready to fertilize the multitude of waiting ovules.

Orchid seeds are very different in another way. Most flowering plants (angiosperms) have double fertilization, producing seeds with both an embryo and a stash of endosperm to feed the seedling as it starts its life. But not orchids. There is no double fertilization, and the tiny seed contains no endosperm to sustain the baby seedling. Even the embryo is much reduced—just a small mass of mostly undifferentiated cells.

Seed of Autumn Coralroot (Corallorhiza odontorhiza), 0.2 mm long! © Freudenstein 2024, CC BY-NC.

When an orchid's capsules dry and split, millions of dustlike seeds are cast to the wind, seemingly with little chance of survival. And yet orchids are said to be one of the most widespread families of flowering plants, both geographically and ecologically! (Brittanica) Seeds and their strategies are what fascinate me most about orchids, far more than the showy diverse flowers. But this introductory post has gone on long enough. So we will stop here, and let the mystery be for now.

"Orchideae" from Ernst Haeckel's Kunstformen der Natur (1899); see source page for names.

Sources (in addition to links in post)

Arditti, J, et al. 2025. Darwin’s prescient letter regarding orchid mycorrhiza. Lankesteriana 25: 83–102. http://dx.doi.org/10.15517/y157kw10 

Brittanica. Orchid. Accessed May 9, 2026.

Freudenstein, JV. 2025. Orchid phylogenetics and evolution: history, current status and prospects. Annals of Botany 135: 805–821. https://academic.oup.com/aob/article/135/5/805/7901162

Wikipedia. Orchids. Accessed May 9, 2026.

By the Shores of Lake Lahontan

Camping on a different kind of beach.

Beachcombing through tufa, not sand.

Last fall, on my way home from California, I drove through northwest Nevada intending to make several brief geostops on the shores of Lake Lahontan. But it was so interesting and so curious that I stayed over two nights. By doing so, I was able to follow in the footsteps of one of the great pioneering geologists of the American West—Israel C. Russell.

I met Russell several years ago in the Mono Basin, not far west of Lake Lahontan. Guided by his spirit, I toured the basin seeing landscapes through his eyes and his words (Russell 1889). He was a terrific writer, and that was a time when geologists weren't constrained by today's conventions of scientific writing. It was wonderful to share his awe and appreciation for the novel geologic features he found.

Israel Russell (source). "his physique gave to the eye little suggestion of that capacity for sustained effort and endurance without which his more strenuous exploration would have been impossible." (Gilbert 1906)

In 1880, Russell joined Senior Geologist Grove Karl Gilbert of the US Geological Survey in a study of what were thought to be relic shorelines, across a huge area in western Utah. Impressed with Russell's diligence and field skills, Gilbert gave him his own project—a survey of similar features to the west in Nevada It would commence the following year.

During the first field season, Russell made a geological reconnaissance "during which about 3500 miles were traversed in the saddle" (all quotes his unless noted]. That winter he prepared a "Sketch" of his findings, starting with a description of the region—expansive, harsh, unusual in the extreme, and "standing in marked contrast in nearly all its scenic features with the remaining portions of the United States."

"The traveler in this region is no longer surrounded by the open, grassy parks and heavily-timbered mountains of the Pacific slope, or by the rounded and flowing outlines of the forest-crowned Appalachians, and the scenery suggests naught of the boundless plains east of the Rocky Mountains or of the rich savannas of te Gulf States. He must compare it rather to the parched and desert areas of Arabia and the shores of the Dead Sea and the Caspian."

Though unlikely to attract "the pleasure-seeker", the region offered a "peculiar fascination" to geologists, for two reasons. First, "the absence of vegetation gives such unusual facilities for investigation". Often not a single tree can be seen for hundreds of miles, and only the rare robust sagebrush offers any hope of shade. Rock and soil are well-exposed.

The barren range beyond the playa was one of Lahontan's many islands and peninsulas.

Second, "the character of the problems to be solved" was irresistible. This was an area rich in geologic novelties, Lake Lahontan being a fine example. Water is scarce to non-existent, and more than a few travelers have chased mirages, gagged on alkaline muck, and perished from thirst. Yet a host of scattered shorelines, tufa deposits, and gravel bars suggest Lahontan was once a huge freshwater lake sparkling in the sun.

Lake Lahontan in its prime, just 13,000 years ago (source).

Routes traveled [red lines] & areas surveyed (Russell 1885); source.

Russell and various assistants would spend two field seasons studying and measuring Lake Lahontan. They determined the elevations of basins (the old lake bed) and terraces on the slopes above (shorelines). They sketched ancient gravel bars and sand spits, and collected samples of the various types of tufa. And they surveyed and mapped nearly 8500 square miles. The result was monumental: Geological History of Lake Lahontan, a Quaternary Lake of northwestern Nevada; Monograph 11 of the US Geological Survey.

"Depth of Lake Lahontan at highest water stage" (excerpt, note depth measurements); source.

"A characteristic specimen of thinolite" [a controversial type of tufa]; source.

From "Map of Lake Lahontan" (c. 20 x 32 inches in its entirety). Note shaded relief overlying contour lines—subject of a future post.

During my visit last year, I toured a northern arm of Lake Lahontan—today's Black Rock Desert and "Lake" Winnemucca to the south.

Black Rock Desert playa is open to driving, fireworks, camping & more (I stayed on the shoreline above). 

From the Black Rock Desert, I drove south along today's Lake Winnemucca, and stopped at a large tufa tower next to the highway. Tufa is sometimes described as a porous limestone; it forms where freshwater meets carbon-dioxide-rich waters, such as springs, streams, and lakes. In his monograph, Russell described three types and partially clarified an "embarrassing" earlier hypothesis for thinolite.

Tufa tower along NV Hwy 447.

Tufa up close.

Lake Lahontan shorelines above today's mostly-dry Lake Winnemucca.

With that stop my visit to Lake Lahotan came to an end. It was much too brief, and I left determined to return.

"The bare mountains reveal their structure almost at a glance, and show distinctly the many varying tints of their naked rocks."

Sources

Gilbert, GK. 1906. Israel Cook Russell. J. of Geology 14:663-667.

Russell, IC. 1885. Geological History of Lake Lahontan, a Quaternary Lake of northwestern Nevada; Monograph 11 of the US Geological Survey.

Russell, IC. 1889. Quaternary history of Mono Valley, California (in USGS 8th annual report). Russell's report was reprinted in 1984 by Artemisia Press, Lee Vining, CA.

Plant Patterns

PATTERN: A naturally-occurring or random arrangement of shapes, colors etc., which have a regular or decorative effect (source); for example, aloe leaves.

Often when I'm immersed in plant photography I wonder: Why am I drawn to patterns? And why are they more beautiful and fascinating through a lens? Have you had this experience?

Attraction to patterns is said to be part of the human condition and I find the argument convincing. Patterns can reveal cause and effect, and understanding cause and effect can contribute to survival. In other words, we've evolved to spot such things. Perceived beauty makes them even more conspicuous.

Now the second question. Why are patterns more engrossing and more beautiful through a lens? For that I don't have an answer, not even a guess.

Here are some patterns my camera and I recently captured.

One-sided Bottlebrush (Calothamnus quadrifidus), southwest Australia.

Naked Lady (Amaryllis belladona), Cape of South Africa.

Matilija Poppy (Romneya coulteri), California Coast (Alta and Baja).

Bay Laurel (Laurus nobilis), Mediterranean Basin.

Bear's Breeches (Acanthus mollis), Mediterranean Basin.

Natal Bottlebrush (Greya radlkoferi), Cape of South Africa.

Chagual (Puya chilensis), Chilean Central Coast (Marktee1).

Winter Wattle (Acacia iteaphylla), southwest Australia.

Manzanita (Arctostaphylos sp.), Central California Coast (1).

The locations in the photo captions reveal another pattern. All of these plants grow between 30º and 45º latitude north and south, on the west or southwest sides of continents, and where summers are dry and winters are wet and mild. These regions share similar vegetation and plant adaptations, and their biodiversity is rich.

This pattern is a phytogeographer's dream! It can be pondered endlessly and mysteries remain. For example, the regions share few if any species (2).

Mediterranean Biomes; original source: Reddit user Simple_Pension_1330.

These are the world's Mediterranean Biomes. Contrary to what you might be thinking, I've been to only one—the Central California Coast. But plants from the others grow in botanical gardens there. Most of these photos were taken during a visit to the San Luis Obispo Botanical Garden (I had to go to the Web for a Central Chilean plant).

Now, some less artsy portraits of my subjects.

Clockwise from upper left: One-sided Bottlebrush, Naked Lady, Matilija Poppy, Bay Laurel (Βικιπαιδιστής).

Clockwise from upper left: Bear's Breeches, Natal Bottlebrush, Chagual (Marktee1), Winter Wattle.

Last but definitely not least, the unknown Manzanita grows in abundance along the trail to Point Sal—a required hike on our visits to the Central Coast.

Notes

(1) On the order of 100 different manzanitas (Arctostaphylos spp.) inhabit the California Floristic Province (source).

(2) Among the five biomes, there's an exception to the no-shared-plants rule. Some plant families and even a few genera occur both on the California Coast and in the Mediterranean Basin, possibly due to a shared ancient flora. More here.

Strange Volcanic Sisters on California's Central Coast

A geo gift for Christmas!

One of my relatives has an eye for fun and fitting gifts. Most recently she gave me a tote bag featuring the Nine Sisters of northern San Luis Obispo County—rocky peaks all in a line, reaching from the town of San Luis Obispo to the sea. The northwesternmost, Morro Rock, is the one everybody knows.

Morro Rock, "the most striking scenic feature on the coast of California" (Fairbanks 1904).

The other Sisters are not nearly as famous, though thousands of people race past them daily. Nor is their number agreed upon. When I was a kid on the Central California Coast long ago, there were seven. Now the more commonly used number is nine. But as geologists know, there are many of these very strange peaks—all of the same rock, all very steep, and all neatly aligned. And they wonder: How did this happen? Why are they here?

The 23 Sisters or Morros (Spanish for "hills") are also known as the Morro-Islay Volcanic Complex.

The Nine Sisters are labeled, with others in between; from northwest (top) to southeast (bottom). See full panorama by SLOhiker.

In October of 1860 William H. Brewer, a recent hire with the brand new California Geological Survey, boarded a steamer in New York City. After a week at sea, he arrived in Panama, crossed the isthmus by railroad in a day, boarded a steamer headed north, and ten days later arrived in San Francisco, where he learned of Lincoln's election. The evening was spent observing celebrations—"fireworks, processions, etc."

After supplies had been secured, Brewer and three others traveled back south by steamer to San Pedro, the port of Los Angeles. In early February, they headed north by horse and mule-drawn wagon, prepared to survey as far as Monterey.

California Geological Survey field party, 1864 (not the 1861 crew); Brewer in chair (Brewer 1930).

As they worked their way north, Brewer wrote letters describing the surrounding country and their adventures in great detail. He mailed them to his brother (where postal service was available), who had been directed to share them with family and friends, and then hold for Brewer's return. Amazingly, all but two or three letters were delivered; they were published in 1930 (source of quotes here).

In early April they entered San Luis Obispo County on terrible roads—"no road in fact, but a mere trail, like a cow path, hardly marked by the track of wheels, and often very obscure." A bad wreck in the Arroyo Grande delayed them for a day as they reassembled and reloaded the wagon. They continued on the so-called 'better' road to San Luis Obispo, arriving a few days later.

Brewer found San Luis Obispo to be "a small miserable town" in a lovely setting:

"San Luis Obispo town lies in a beautiful, green, grassy valley, about nine miles from the sea. ... This valley is more like a plain, from four to six miles wide and fifteen or twenty long, running northwest to the ocean."

They camped near a butte that was "beautifully rounded, about eight or nine hundred feet high and perfectly green."

Brewer's party likely camped near today's Cerro San Luis (Leif Arne Storset photo).

Though beautiful, the butte was quite strange in the way it rose so suddenly from the plain. And there were many such buttes, all equally odd, all curiously aligned.

"These buttes are a peculiar feature, their sharp, rugged outlines standing so clear against the sky, their sides sloping from thirty to fifty degrees! ... A string of these buttes, more than twenty in number, some almost as sharp as a steeple, extend in a line northwest to the sea, about twenty miles distant, one standing in the sea, the Morro Rock, rising like a pyramid from the waters."

"Through this plain rise many sharp peaks or 'buttes'—rocky, conical, very steep hills" (hakkun photo).

An unnamed butte, one of many (Ronn Koeppel photo).

As for their geology, Brewer noted only that the buttes were "mostly of volcanic origin, directly or indirectly". If he thought it odd to find volcanos here, he didn't say (1).

Brewer is often credited with today's name: "these buttes are in a line, nine in number, and I propose to call them the Nine Sisters." But in reading his letters I found no such statement. He never called them the Nine Sisters and counted at least twenty. Claude AI found this false quote in multiple places, "copied uncritically from source to source".

Before leaving San Luis Obispo County, Brewer and a companion climbed and measured the Santa Lucia Mountains. It was a lovely day—cool and clear—and views from the crest were worthy of contemplation.

"the breakers on the shore were perfectly distinct twenty miles distant! [italics his] To the southwest and west lay all the lovely plain of San Luis Obispo, the buttes rising through it—over twenty were visible—brown pyramids on the emerald plain. We sat and contemplated the scene for over an hour before leaving."

"brown pyramids on the emerald plain" (Basar photo).

About forty years later, Harold W. Fairbanks of the US Geological Survey surveyed, mapped and described the geology of the San Luis Quadrangle (west-central San Luis Obispo County). He too was struck by the curious line of rocky peaks and ridges, which he called the "San Luis buttes".

"South of the town of San Luis Obispo there begins a line of peaks and ridges which extends northwestward for about 16 miles. It terminates in Morro Rock, lying in the ocean off Morro Bay. This series of buttes constitutes the most striking topographic feature of the quadrangle. There are about 12 ... Many of them are almost completely isolated and rise from the open valleys with bold and frequently precipitous rock faces." (Fairbanks 1904, source of quotes here).

San Luis Obispo c. 1903, with two of the San Luis buttes behind.

"Hollister Peak rises from a base but little above tidewater to a height of over 1400 feet" (Ronn Koeppel photo).

Fairbanks knew the San Luis buttes were volcanic, the rocks made that clear. He identified dacite and andesite in roughly equal abundance; dacite is now considered the dominant type.

Dacite contains visible crystals set in a fine-grained gray groundmass—classic porphyritic texture. This led Fairbanks to call the rock dacite-granophyre ("phyre" from porphyry), a term no longer in standard use. But he was correct about the porphyritic texture, and that led him to another conclusion, also correct. The San Luis buttes are volcanic plugs formed at shallow depths, not extruded magma. They were exposed later when erosion removed the softer surrounding rocks.

Dacite: plagioclase feldspar (large whitish crystals), biotite and quartz in a gray groundmass (Johnston 2021).

In the Geologic History section of his report, Fairbanks tried to place the volcanos in the greater scheme of things, but their age "could not be definitely ascertained from any observations made." It appeared that their intrusion had not deformed adjacent Cretaceous rock, and therefore the volcanos must be older. He assigned them to the early Cretaceous Period, between 140 and 100 million years ago (2). We now know they are much younger, emplaced 27 million years ago (Beck & Johnston 2011).

Like Brewer before him, Fairbanks did not try to explain why these volcanos had erupted here. It was an understandable omission. Geology was still a young science; sixty years would pass before geologists came up with widely-accepted explanations for volcanism.

Excerpt from Fairbanks's geologic map; San Luis buttes are the orange blobs from upper left (Morro Rock) to lower right (Islay Hill). Click on image to view.

The great progress geologists have made in deciphering the hows and whys of landscapes is due largely to the theory of plate tectonics. In brief, the Earth's surface consists of giant plates—on the order of a dozen large ones and many smaller. Though massive, they are not stationary. They shift, jostle, collide, rise and sink, expand and contract, and deform each other in various ways. Their movement is much too slow for us to sense, just 2 to 10 cm per year, like the growth of a fingernail. In contrast, the results are spectacular—for example mountain ranges, ocean basins, earthquakes and volcanos.

But in spite of our understanding of plate tectonics, the volcanic buttes between San Luis Obispo and the sea remain puzzling. The problem is their location. Volcanos can't erupt just anywhere; there must be a source of magma. But magma doesn't occur just anywhere. It forms with melting of the mantle, the immense mass of solid but soft rock that lies well below the Earth's surface.

Earth's internal structure (IsadoraofIbiza). The voluminous mantle is the source of volcanic magma, but only under the right conditions.

Though the mantle underlies all of Earth's crust and forms 84% of its volume, it only melts sufficiently for volcanism in special situations. The common ones are: (1) mid-ocean ridges, where two plates are moving away from each other; (2) hotspots perhaps created by rising plumes of anomalously hot mantle (they're controversial); and (3) subduction zones where one tectonic plate dives under another deeply enough to melt (Nelson 2015). The Sisters fit none of these scenarios.

California's Central Coast 40 million years ago, expected areas of volcanism circled in white. But the Sisters erupted into a thick stack of sedimentary and metamorphic rocks (from Johnston 2021; annotations mine).

The Morro-Islay volcanos all erupted into a thick stack of sedimentary rocks (3), well away from the usual tectonic settings. And the amount of magma was far too little to have been produced by a hot spot (think about all the volcanic rock in the Hawaiian islands!). So why did these volcanos erupt here? Because 27 million years ago there was a window of opportunity—specifically a slab window.

If we were to visit the coast of North America 27 million years ago and look west, we would see ocean to the horizon. But something very interesting was going on below the surface. Not far away, the seafloor was spreading along a mid-ocean ridge, with mantle rock welling up and melting, and volcanos erupting (yes, underwater!).

Mid-ocean ridge in action; orange upwelling is melted mantle (USGS).

That mid-ocean ridge was the boundary between two tectonic plates—the Pacific to the west and the Farallon to the east. The entire system was moving eastward, forcing the Farallon Plate to dive under the North American plate. This was a straightforward example of subduction until the mid-ocean ridge arrived. When it reached the subduction zone, the Farallon Plate continued sinking eastward while the Pacific Plate moved northwest. No longer connected, they opened a slab window where mantle could rise, melt, and produce the magma that formed the Sisters.

And there would be more drama—not just volcanos but also earthquakes. With the Farallon Plate gone, the Pacific Plate continued moving northwest, but now along the coast of North America. Subduction was replaced with a transform fault moving in slips and jerks, periodically wreaking havoc (earthquakes). This slab window turned out to be a major tectonic event—giving birth to the San Andreas fault as well as the Sisters!

Creation of the San Andreas transform fault (parallel but opposite arrows) with the arrival of a mid-ocean ridge (dark pink band) (USGS, highly modified).

To end this story, let's return to its beginning—to Morro Rock and the words of William H. Fairbanks. In Economic Geology, the final section of his report, he wrote:

"The buttes extending from San Luis Obispo northwestward to Morro Rock furnish excellent and durable stone for building purposes. A quarry has been opened on Morro Rock for the purpose of supplying material for the Port Harford breakwater, and blocks of any size can be obtained. It is to be hoped, however, that the grandeur and symmetrical proportions of this mass will not be marred, as equally good material can be obtained from the other buttes."

Morro Rock was quarried off and on from 1889 to 1963. It now belongs to the State of California, and has been designated both a state and historical landmark (more here). And fortunately, its "grandeur and symmetrical proportions " are still with us.

Notes

(1) Brewer's very brief discussion of the origins of the buttes isn't surprising. He was a surveyor, not a geologist. In fact his title was Principal Assistant in charge of Botanical Department. But he was an astute observer, shown by his tally of the buttes for example.

(2) Fairbanks was not convinced that the San Luis buttes were Cretaceous in age. In his Geologic History section he noted "There were at least two epochs of igneous activity during the Cretaceous, and three if the formation of the San Luis buttes be included."

(3) The sedimentary rocks intruded by the Morro-Islay volcanos are part of the Franciscan Complex— a diverse assemblage of sedimentary and metamorphosed rocks accreted to the North American plate during subduction—an accretionary wedge.

Sources

Beck, MD, Johnston, SM. 2011. U-Pb geochronology and geochemistry of the Morro-Islay volcanic complex, southern California. Abstract.

Brewer, WH. 1930. Up and down California in 1860–1864 (introduction by Francis P. Farquhar). Oxford University Press. Available at Hathitrust.

Fairbanks, HW. 1904. Description of the San Luis Obispo Quadrangle, California: Geologic Atlas. San Luis Folio 101, USGS. 7 PDFs

Johnston, SM. 2021. The Morro-Islay Volcanic Chain and what's a slab window anyway? Video lecture. Highly recommended.

Morro Bay National Estuary Program. 2024. A Geologic History of Morro Rock (includes the geology of the Sisters, with simple diagrams).

Nelson, SA. 2015. Structure of the earth and origins of magma. Lecture outlines; very clear!

Sierra Club, Santa Lucia Chapter. The Nine Sisters of San Luis Obispo County. Web Archive.

Wikipedia's Morro Rock article includes the geology of the entire Morro Rock-Islay Hill Complex.