According to the flora I use in this region, Flora of the Yosemite Sierra by the eminent Dean W. Taylor, “This variant is an exclusively high-altitude expression of the highly variable C. umbellatum, but it consistently differs in growth form, the deeply seated roots being beset with old leaf bases, and the consistent polycarpic life-history.” Classically stated and verifiably accurate; however, the current Jepson Manual places this variety in synonymy, simply lumping it into Calyptridium umbellatum. The plants I kneel over certainly appear distinct to me, as well as stunning in flower in this alpine setting. Predictably, I find no seed, as all the plants are still in flower; however, I am smitten by this taxon and have no reservations about returning. I am indebted to Dr. Taylor not only for elucidating the differences in the pussypaws’ elevational expressions, but also for providing us with his flora, the first and sometimes only one I use while in the area. It will be an honor to grow this variety of pussypaws in the Sierra section of the Regional Parks Botanic Garden, in our new crevice rockery!
Why am I excited about building a new crevice rock garden? Because the alpine zone is one of the most interesting parts of California and the zone I visit most often. I did, in fact, return to collect seed of the alpine form of pussypaws, as well as seeds of many other true alpines; and I am thrilled to grow these out in the garden so that visitors can share in all the wonders found in the highest reaches of our state. To grow many of these plant taxa in the Berkeley Hills (east of Berkeley, California, at an elevation of less than 2,000 feet/600 m) will require this type of garden crevice bed. It will be impossible to completely emulate the wind, the cold, the high level of UV light, and the lack of antagonistic organisms found in the high Sierra. Nevertheless, I am confident the new crevice rock garden will satisfy many of the conditions necessary. We want to grow and display as many Sierran plant taxa as possible, preferably those of the alpine region.
Additionally, as a part of our garden’s mission, we endeavor to display plant specimens in a manner that suggests a realistic setting in nature. To make the rock project look natural I referred to my favorite examples, those from the wild. For me, the most interesting alpine plants, and the most beautiful scenery, are located in regions of the Sierra that are comprised of geologic formations referred to as roof pendants. Simply put, a roof pendant is a metamorphosed formation, either sedimentary or volcanic, that was initially deposited before the most current Sierra uplift. By applying pressure and heat over time, the ensuing uplifting granitic magma subsequently altered or metamorphosed the original material. High above Mono Lake, on the Sierra’s east side, resides one of my favorite metamorphosed sedimentary, or metasedimentary, portions of the “range of light,” the Upper Parker Creek drainage; it is also the area where I collected the alpine pussypaws. My desire to re-create rock outcrops similar to this region is my inspiration for our crevice garden.
To get a feeling for the large project of building a full-scale crevice garden, I first assembled a smaller crevice trough. I wanted to gauge not only the benefits to alpine plant horticulture but also the receptiveness of the Friends, docents, and general public to the potential installation of a very large-scale version of this style of rockery. The trough is a roughly two-foot by three-foot (60 cm by 90 cm) rectangular planter with more-or-less vertically oriented flagstone that rises about 18 inches (46 cm) above the lip of the container and is backfilled with a very sandy, mostly mineral, growing medium. I am happy to say that several alpines— such as rockfringe (Epilobium obcordatum), beaked beardtongue (Penstemon rostriflorus), gray chickensage (Sphaeromeria cana), and Sierra wild rye (Elymus sierrae)—have either bloomed here for the first time (rockfringe) or reliably bloomed (beaked beardtongue). Perhaps more importantly, almost all visitors, Friends, and docents have been extremely interested in the concept. These promising horticultural results and our receptive visitors have renewed my interest in growing even more taxa of these challenging alpines.
Preceding any groundbreaking there are many planning steps to attend to, and now that I had a natural model envisioned it was time to get started. The first task was to choose a location for the crevice-style rock garden. Fortunately, James Roof, our founding director, long ago had a series of successful alpine beds above our north lawn and below the Garden’s Redwood section. This area provides great exposure for the alpines. It faces east and receives morning to early afternoon sun while staying cooler in the late afternoon as it is shaded by the Redwood section’s overstory trees. It is important to avoid prolonged excessive heat in the root zone of alpines, as this will compromise their health. One way to do this is to limit the duration of direct sunlight, although that could compromise flowering. These historic alpine beds performed well until the overly aggressive root systems of nearby trees and shrubs invaded the root zones of the slow-growing alpines. Nevertheless, we agreed to site the crevice garden here, with a sound plan to exclude the tree roots by laying down two layers of geotextile soil-separator fabric to impede or prevent their entrance into the new crevice-garden beds.
The stone we chose comes from a family-owned quarry located in the foothills of the Sierra Nevada west of the historic town of Mariposa. The appropriately named Mariposa-Yosemite Slate Quarry is owned and operated by David Butler, a very knowledgeable and capable descendant of early Mariposa settlers. The stone is likely the most beautiful I have yet worked with and is a remarkably close match to the high-elevation metasediments I adore around Tioga Pass.
We used the quarry’s largest “stand-up” pallets of slate and even larger and thicker quartzite slabs and boulders set vertically on edge to simulate an extreme uplifted and metamorphosed sedimentary deposit. This material is mined from a region known as the Mother Lode belt, not too far from Yosemite National Park. It is also metasedimentary, though likely not as old as the metasediment in Upper Parker Creek. However, in places, the Parker Creek rock outcrops look exactly like the new crevice garden’s Mariposa slate with its rich browns and reds and vertically oriented crevices. The scree paths between the crevice ridges in the Botanic Garden are also identical to the trail surface in the Parker Creek drainage.
I want the crevice-garden structure to inspire awe not only in our guests but also in me. I want the massive rocks to evoke the same feelings I get when I gaze upon the eastern escarpment of the Sierra Nevada from the Inyo Mountains or Highway 395. This requires walls that rise steeply and sharply from the base and edges of the project. Setting these large stones vertically and close to the edge of the paths is a perfect way to bring the diminutive alpine plants closer to the viewer’s eyes; in the past, in the shorter beds, these significant and important plants were lost below the viewer. In addition, this vertical orientation provides an excellent, perfectly drained, long root run for the many deeply tap-rooted alpines we intend to display. For example, alpine spring beauty (Claytonia megarhiza) can have a taproot that is four to six feet (1.2 – 1.8 m) long in ideal conditions. Our crevice garden has close to six feet (1.8 m) of rooting depth in its deepest portion of the center ridge. This makes me so happy—I hope it will make our alpines happy too!
This awesome, vertical, massive, crevice drama adds up, especially by weight! We purchased 116 tons of stone and an equivalent amount of crevice backfill (used as anchorage and rooting media among the stones) for a total of approximately 230 tons of material to be imported for the project. Also, we had to excavate and remove a considerable amount of clay soil and lawn for the sand base, as well as most of the old alpine bed’s incompatible stonework. This required heavy equipment, and experts to operate it. Fortunately, in the Regional Park District we have one of the finest roads and trails crews I know of, and they were willing to help us out with the heavy lifting. I am indebted to both Rodney Smith and Bill Surges from Roads and Trails, as their expert equipment operation and hard work made this project possible. For me to be inches from an 800- to 1,000-pound (360 - 450 kg) suspended boulder requires trust and confidence in the skill and control of the operator. That skill and control can only come from a lifetime of training and experience. Bill and Rodney are masters at their craft and have this level of experience.
The final component of the project, and perhaps the most important horticulturally, is the backfill medium used to fill the crevices. For the alpine plants I want to grow, we need a growing medium that is well-drained, well-aerated, and largely mineral in content. To start the process of backfilling the crevices, more than 90 tons of washed river sand was purchased and transported into the Garden. The sand was primarily used as a leveling and anchoring base for the vertical slate and schist pieces that sometimes weigh more than 1000 pounds (4500 kg), but it is also a suitable medium for alpine plant growth. The sand was placed in the lower portions of the crevices and was gradually mixed with the next component as we continued to fill them.
Expanded shale is the next major component that we decided upon and is for me the “holy grail” of horticulture. It is formed when shale is crushed and heated in a kiln to 2,000 degrees Fahrenheit (1093°C). This process causes the tiny air spaces in the shale to expand. The resulting product is called expanded or vitrified shale. Expanded shale can hold up to 40% of its weight in water and is excellent at retaining and then releasing essential plant nutrients as well as the water. It is lightweight and stable and has proven itself in many crevice gardens across North America. To the expanded shale we mix in a small amount of compost (10% by volume). For additional alpine plant health, a graded 3/8-inch (9.5 mm) expanded shale gravel is placed around the root crown to ensure this vulnerable zone has the sharp drainage required to keep the stem and the root from rotting. This larger sized expanded shale is also proving to be resistant to washing out during rainfall and overhead irrigation. As I start to plant some choice alpines in the nearly completed beds, I am excited to see the positive results that they are already exhibiting. I have attempted to grow many of these species before, and they have never looked this good in the outdoor beds; others, we have never grown. I believe that this area of the Sierra section is the most suitable we’ve ever had in which to grow alpine plants, and I am very eager to start more of this year’s seed collections in pots in the hope of planting them out as soon as next year.
As construction progressed, I could not stop envisioning how each stone placement was creating the perfect location to grow the beautiful Sierra Nevada alpine plants that I have always admired. I was constantly transported to my favorite Sierran haunts and imagined each crevice as a scramble up a steep couloir to look upon fine alpine plants. I longed to return to the mountains. As soon as the heavy equipment portion of the project was completed, my wife and I were on vacation and on our way to the alpine zone of the Sierra Nevada with my Inyo National Forest collecting permit.
I am blessed to have a life partner who loves to vacation with me in the alpine region of the high Sierra and botanize. Carrying all our belongings on our backs and keeping as close to the earth as possible in what is, to me, the most pristine portion of California—there is nothing better in life! Only stopping once for gas and packing all the supplies needed for the ten-day backpacking trip: this is the perfect prescription for the pandemic blues of our two-person pod. Even during those gale-force winds, we continued to search together for the beautiful alpine cushions and celebrated the forces that helped create this wonderful alpine environment. We camped in one location for nine days, becoming intimate with the diminutive flora of this region’s alpine zone, and I returned with several true alpines for the Botanic Garden.
Two years ago, when the construction portion of the crevice garden started, I compiled a list of plants I desired to grow upon its completion. Early last year I applied for the collecting permit with the Forest Botanist of the Inyo National Forest, describing our Sierra alpine crevice garden project and including photographs of its first phase. I also included the list of choice alpine species that I felt we could successfully propagate and grow, and requested permission to obtain propagules. Below are descriptions of a few of the notable collections.
Rapidly rooted in the nursery under lights and over heat mats, three fine species of beardtongues (Penstemon spp.) are now planted out in the new crevice garden. We now grow five of the eight species of beardtongue that make it to at least 11,500 feet (3500 meters), the elevation widely considered by alpine ecologists as the lowest elevation for alpine species growth in the Sierra Nevada. Although it is not the stereotypic mat or cushion of the alpine, beaked beardtongue (Penstemon rostriflorus) is very fast to root from vegetative cuttings, and within weeks I had already planted out several bare-rooted propagules in the new crevice garden, with more to come. Beaked beardtongue had already bloomed profusely in the crevice trough for the last few years, and I am excited to see how this true alpine, with its intense scarlet flowers, develops in the new crevice garden substrate. Also planted out as a bareroot cutting is Davidson’s penstemon (Penstemon davidsonii). This little gem fits the alpine flowering mat profile, and its unusually large blue-violet to blue-purple flowers are always amazing to me. I suspect the few high-elevation pollinators that enter the corolla are amazed too! Davidson’s penstemon is a veritable crevice garden specialist and one that is worth close inspection. The last of the three new beardtongues, Sierra beardtongue (Penstemon heterodoxus var. heterodoxus), is my favorite, as it is the one that ranges highest of all those found in the alpine zone. Found no lower than 8,858 feet (2,700 meters), it makes itself at home all the way up to 12,800 feet (3,900 meters). It is also easy to key out in the regional flora. I enjoy looking for its whorls of flowers with their interesting stalked glands, always worth magnified observation.
Another group of interest to me is the wild buckwheats (Eriogonum spp.). This genus is one of the largest (and most diverse) in California. The Jepson Manual lists 117 species and 123 varieties. Only ten of these species and one variety make it to the rarefied altitude of 11,500 feet (3500 meters), and I was able to obtain seed of three of them. One of my all-time favorites is Lobb’s buckwheat (Eriogonum lobbii). It has the most interesting habit of laying its flowering stems on the ground rather than growing in the typically erect posture of most buckwheats. I grew this species once to flowering maturity and then lost it to an herbivorous moth or butterfly larva— but not before I could take a photo. I hope the larva was from one of the beautiful “blues” (Euphilotes spp.) that are known to use wild buckwheats as larval food sources. I have collected seed again and believe that our visitors (both butterflies and humans) will be seeing more of Lobb’s buckwheat in the new crevice garden.
A second Eriogonum species, and the most taxonomically interesting to me, is the frosted wild buckwheat (Eriogonum incanum). It is one of only three species of wild buckwheat in California that is dioecious, meaning functional male and female reproductive parts are found on separate plants. Recall that there are over 200 Eriogonum taxa in California, so this is a rare condition in the genus. It is interesting to note that when the two sexes are mature one can see inflorescence differences, as the female plants develop more red color in the corollas and tend to become more prostrate, while the male flowers are noticeably branched and maintain a more yellow, spherical, upright inflorescence. I look forward to displaying both male and female plants of this unusual alpine buckwheat for all to enjoy at the Botanic Garden.
A third and more challenging Eriogonum collection was that of an adorable Sierra native, the raspberry (or White Mountain) buckwheat (Eriogonum gracilipes). While it is known to grow in the Sierra Nevada, I have only seen it in the Inyo and White Mountains of far-eastern California, and it was there that I was able to find good seed of the species. Ellen and I spent a windy November weekend avoiding the first snowfall in the Sierra by heading up Mazourka Canyon in the rain shadow at Badger Flat in the Inyo Mountains. It was the perfect location to escape the pandemic-weary crowds for our ninth wedding anniversary as we saw no one else on our trip. This late-season collection trip yielded a few choice taxa, including the ripe raspberry buckwheat seed. I hope we get to see these rich red spheres of flowers soon!
Let us not forget the carices (the sedges)! I have heard it uttered by otherwise fine botanists that “life is too short for Carex.” I respectfully disagree. Carex is a vast genus with over 2,000 species worldwide. It is also the most diverse genus to be found in my beloved alpine zone, not to mention a favorite food for those cute rabbit relatives, the pikas. The genus Carex has 29 species growing to at least 3,500 meters (11,500 feet). (The next most diverse genus is Draba, with fewer than half the species, 14, in this alpine zone.) The Tahoe sedge (Carex tahoensis) is particularly intriguing to me as it belongs to the taxonomically tricky sedge group known as the Ovales section. The Ovales includes species that are remarkably similar to the trained eye and generally identical to the untrained observer. In the crevice garden, we are growing several plants from a collection made over three years ago at the type locality on Lake Tahoe’s Mt. Tallac. I have fairly confidently keyed these to Carex tahoensis. Records indicate that the type specimen for Tahoe sedge was housed at UC’s Jepson Herbarium, but, alas, it is apparently no longer there. Additionally, Tahoe sedge was ranked by the California Native Plant Society (CNPS) as being of limited distribution (California Rare Plant Rank [CRPR] 4.3). Having a missing holotype, along with its rarity, was more than enough justification for me to grow Tahoe sedge at the garden. This year I also collected in the Parker Pass region what appears to be particularly good Tahoe sedge seed.
And now, at last, the sedge I am most thrilled about has been recognized as extremely rare and is ranked by the CNPS as CRPR 1B.3 (Plants rare, threatened, or endangered in California and elsewhere). Not only were we fortunate to obtain a small amount of seed; it was also a great opportunity to conduct rare plant monitoring and submit the results to the botanist in charge of the Inyo National Forest as well as the rare-plant botanists at the CNPS. While thinking of this relatively recently described sedge, I am especially saddened. The Tioga sedge (Carex tiogana) represents a species discovered and formally described by one of my botanical heroes (and the author of my favorite flora), Dean William Taylor. Tragically, Dr. Taylor passed away last November. I will always remember him, always refer to his work, and I will do my best to grow his Carex here in the garden.
The construction of this crevice garden has been a highlight of my 15 years at the Regional Parks Botanic Garden, and I am privileged to have been present and involved at every moment of its creation. It is a fitting addition to our garden and is already generating a healthy amount of attention from the horticultural community. The project is a wonderful testament to the vision and dedication of our garden’s director, Bart O’Brien, and of the Garden Supervisor/Horticultural Specialist, Liz Bittner, as well as of all our garden staff. It is also a great example of the commitment and generosity of the Friends of the Regional Parks Botanic Garden; without their financial contribution specifically for the crevice garden, this bold project could not be accomplished. I look forward to stewarding the new crevice garden long into the future, and I thank everyone who contributed for their critical support.