Shoreline habitats around water bodies with fluctuating water levels present challenging conditions for most plants. Such habitats occur along the shores and in the shallows of man-made reservoirs and natural depressions containing seasonal lakes. These habitats may be either dry and exposed for several years in succession during periods of drought, or continuously inundated during periods of above average precipitation.
Some plants readily tolerate annual cycles of inundation and exposure, but fewer can thrive where there is both multi-year dewatering and multi-year inundation. Examples of such habitats in northern Mono County include the natural shallow seasonal lakes on Dry Lakes Plateau, and the shallows of Bridgeport Reservoir and Grant Lake Reservoir.
Surprisingly, some plants actually thrive in receding shoreline habitats, both natural and artificial. Some are annuals, some are perennials, some are native, some are introduced. They are most prevalent where the ground is nearly level or sloping only gradually; steeper slopes tend to be eroded, with thinner, less favorable substrates. The following highlights several species I’ve seen flourishing in these habitats during the recent series of drought years.
Taraxia tanacetifolia (Tansy-leaf evening primrose) can be the most abundant and colorful plant in receding shoreline habitats. In low-water years it creates a spectacular carpet of yellow across the exposed eastern shallows of Bridgeport Reservoir. Similar displays can occur across the beds of both seasonal lakes on Dry Lakes Plateau. These carpets of yellow can be seen from miles away.
Tansy-leaf evening primrose is a stemless, taprooted perennial with leaves that are deeply and irregularly pinnately lobed, 4 petals up to an inch long that open bright yellow and fade to orange, and a capitate stigma that extends beyond the 8 anthers. It looks a lot like Oenothera flava, but Oenothera flowers have a prominently 4-branched stigma.
Potentilla rivalis (Brook cinquefoil) can be abundant too, but not necessarily together with the Taraxia, and its yellow flowers are much smaller and less showy. It can, nevertheless, form a patchy to dense groundcover in strands along the east shore of Bridgeport Reservoir and on shallow flats near the south end of Grant Lake Reservoir. This is a widespread species, found in many ecoregions and in a variety of habitats across western and central North America. It isn’t restricted to receding shoreline habitats, but it’s well adapted to be very successful in some such areas.
Brook cinquefoil is an annual or biennial with ascending stems. Its leaves are palmate with 3–5 leaflets; it has open, branching (cymose) inflorescence with many flowers, but tiny petals barely 2 mm long. It is a prolific seed producer, and you are likely to see uncountable thousands of these tiny achenes scattered on the ground among the plants.
Potentilla newberryi (Newberry’s cinquefoil) is known mostly from the shallows and shorelines of natural seasonal lakes in northeastern California (Modoc Plateau), south-central Oregon, and northwestern Nevada. It’s been collected in west-central Nevada from Silver Lake in Washoe County south to a pond in the Pine Nut Mountains in Douglas County. In 2021 it was discovered along the sandy/gravelly eastern shore of Bridgeport Reservoir, with additional observations there in 2022. Also in 2022 it was found on the south shore of Lake Tahoe.
When flowering, this plant is clearly Potentilla-like (though it was originally described as an Ivesia), with pinnately compound leaves and prostrate to decumbent stems, and is unusual among cinquefoils of our region in having white petals.
Verbena bracteata (Bigbract verbena) looks unlike anything else in this area, with its many narrow-triangular, hairy bracts along many-flowered spikes on long, lax stems. This is another widespread (mostly western) North American native, usually found at pond or lake margins or other open, disturbed places. These photos show it at the south end of Grant Lake Reservoir.
Persicaria amphibia (Water smartweed) flourishes during periods of shallow inundation rather than drought, but clearly it survives the dry periods easily. These photos show it rooted in a sandy beach at Bridgeport Reservoir. When the water is high, this site is a few feet under water. When inundated, the plants have several ovate-elliptic leaves floating on the surface, and a terminal spike of bright pink flowers.
Artemisia biennis (Biennial wormwood) occurs in moist, disturbed sites across much of North America. It’s locally common in sandy soils at Bridgeport Reservoir, especially north of the boat launch at Ramp Road. The Flora of North America considers Artemisia biennis to be native in the northwestern United States and possibly introduced in other parts of its range; it is introduced in Europe.
The above is far from being an all-inclusive list of plants that can be found in these habitats. The list will vary from one lake or reservoir to another, depending on a variety of factors. The take-away for me, after looking at Bridgeport and Grant Lake Reservoirs particularly, is that the vegetation of receding shoreline habitats is not all weedy—some interesting and unexpected native plants are likely to be found there too.
Plants of the Bodie Hills, January 2023 Edition, is now available on the Downloads page (a free PDF). As in previous years, the new edition contains additions, corrections, nomenclatural updates, and refinements to the keys. A key to genera in the grass family (Poaceae) has at last been added.
New additions to the flora this past year are:
Astragalus platytropis (Broad-keeled milkvetch)
Eatonella nivea (Woolly bonnets or White false tickhead)
Eriogonum cernuum (Nodding wild buckwheat)
Glossopetalon spinescens var. aridum (Spiny greasebush) (Crossosomataceae)
Many of these finds were made not by me, but by others posting their observations to iNaturalist (thanks to all who do this!). All observations within the Bodie Hills can be seen HERE.
As before, you have two options for how to use this document: 1) load the PDF onto a mobile device or 2) print the PDF yourself.
Using a mobile device: I’ve found the PDF to be quite readable on my iPhone (in the Books app), although it helps that I’m near-sighted. It’s even easier to read on an iPad, other tablet, or laptop.
Printing the PDF: You can print the PDF yourself or at a local print shop. I highly recommend printing the 124 pages 2-sided to conserve paper and reduce bulk and weight in the field. A comb or spiral binding, binder clip, or other binding will hold it together.
Your additions, corrections, comments, or questions are always welcome.
Here are a few plants I was pleased to see last year while roaming the Bodie Hills:
Two varieties of Great basin wild buckwheat (Eriogonum microtheca) are common in the Bodie Hills (var. laxiflorum and var. ambiguum), and a third (var. alpinum) is likely present in a few areas. Several other varieties occur throughout the deserts and mountains of western North America. The characters that distinguish these are, aside from flower color, fairly subtle differences in stem and leaf vestiture (hairiness), leaf size, and plant height. Most of the varieties are difficult to identify with certainty from photographs alone, but some have narrow geographic distributions, which reduces the number of possibilities in many areas to just two or three.
I’ve been wanting to understand these taxa better. So, I’ve mapped the documented locations of each, and I share those maps with you below, along with some notes on identification and links to photos.
First, a few notes:
Is the epithet microthecA or microthecUM ? The spelling was was originally published in 1848 as Eriogonum microtheca, but since 1858 microthecum has been in general use. Apparently, this was an error—probably introduced and widely accepted, because it “sounds right” and the usual practice is to have the genus and epithet endings agree in gender (-um is neuter, -a is feminine). Recently, as microtheca became accepted once more, there was a proposal to conserve microthecum, which (unfortunately in my opinion) did not prevail. So, microtheca it is, but in references that have not been recently updated, microthecum is still widely used. Confusion on this important issue will persist for decades to come.
Data sources: The maps are based mostly on specimen location data downloaded (as KML files) from the Consortium of California Herbaria (CCH), served by the CCH2 data portal and the Intermountain Regional Herbarium Network (IRHN). Several maps include additional “research grade” observations downloaded (as CSV files) from iNaturalist. The map for variety microtheca is based mostly on data from the Consortium of Pacific Northwest Herbaria (CPNWH). Caveat: Some collections or observations may be misidentified or have mis-mapped coordinates, so some locations shown on these maps may be incorrect. The geographic ranges suggested by these maps should be considered very approximate.
Mapping software: The maps were compiled using Quantum GIS (QGIS), a free, open source Geographic Information System that I’m gradually learning to use. The base map is a combination of “Stamen Terrain Background” and “ESRI Terrain” web map services. Additional minor cleanup and formatting was done in Adobe Photoshop and Adobe Illustrator.
Map 1, var. laxiflorum, var. simpsonii , and var. microtheca. These are the three most widespread varieties. Var. laxiflorum (Great Basin wild buckwheat) (photos) is common across the central and northern Great Basin, and the eastern Sierra-Cascade ranges, up to eastern Washington. Var. simpsonii (Simpson’s wild buckwheat) (photos) is common across the central and southern Great Basin to the western Rocky Mountains and Colorado Plateau. These two are very similar, but the leaf margins of var. simpsonii are revolute (turned under) or nearly so; those of var. laxiflorum are not.
Variety microtheca (Slender wild buckwheat) (photos, specimen images) occurs mostly from central Washington to central Idaho. Its flowers are yellow (flowers of var. laxiflorum and var. simpsonii are mostly white), but so are the flowers of var. ambiguum, which also extends into eastern Washington and western Idaho (see Map 2). The flowering stems and inflorescence branches of var. microtheca are usually glabrous (hairless); those of var. ambiguum are tomentose (with densely interwoven, generally matted hairs) to floccose (with tufts of soft woolly hairs, the tufts often deciduous).
Map 2, var. ambiguum and var. schoolcraftii. Variety ambiguum (Yellow-flowered wild buckwheat) (photos) occurs in the eastern Sierra Nevada and western Great Basin from Inyo County to southeastern Oregon. It is similar to and sympatric with var. laxiflorum, except for its yellow perianth. Its range also overlaps with var. microtheca in eastern Oregon; but, as noted above, the flowering stems and inflorescence branches of var. microtheca are usually glabrous, while those of var. ambiguum are tomentose to floccose.
Variety schoolcraftii (Schoolcraft’s wild buckwheat) (photos) has a very narrow distribution southeast of Honey Lake, in Lassen, Washoe, and perhaps also Plumas counties. It’s very similar to var. ambiguum (yellow flowers and tomentose/floccose herbage), but has slightly larger leaves, flowers, and fruits.
In var. ambiguum: leaf blades are mostly ≤ 0.6 cm wide; flowers are mostly < 2.5 mm long; involucres are 2–2.5 mm long; achenes are 1.5–2 mm long. In var schoolcraftii: leaf blades are 0.5–1.2 cm wide; flowers are mostly 2.5–3 mm long; involucres are 2.5–4 mm long; achenes are 2.5–3 mm long.
Map 3, var. alpinum. Variety alpinum (Sonora Pass wild buckwheat—though based on its distribution I think it should be “Mono” wild buckwheat) (photos) is known mostly from the eastern Sierra Nevada (and the Sweetwaters, Bodie Hills, and Glass Mountain) in Mono County, plus a few nearby locations in Alpine and Tuolumne counties. With white to rose or reddish corollas, it resembles var. laxiflorum (common throughout the same area), but its stature is shorter, leaves are shorter and narrower with revolute margins, and hairs are often whiter than in var. laxiflorum. It seems to favor the crests of glacial moraines, arid hilltops, and high ridge habitats.
Map 4, var. lapidicola, and var. panamintense. Variety panamintense (Panamint wild buckwheat) (photos, specimen images) is probably restricted to the desert ranges of central Inyo County (one collection in the southern Sierra Nevada may be misidentified). Variety lapidicola (Pahute Mesa wild buckwheat) (photos, specimen images) is known from the Inyo Mountains of Inyo county, the Pahute Mesa/Rainier Mesa area of Nye County, and other scattered locations in central and eastern Nevada as far north as Elko County.
These both differ from var. simpsonii and var. laxiflorum in having flowering stems and inflorescence branches generally glabrous; hairs, if present, are generally brownish or reddish rather than whitish. Both have leaf blades elliptic, and the margins not revolute.
Variety panamintense is a shrub 3–6 dm tall, with leaf blades broadly elliptic, 6–18 mm long × 3–8 mm wide, brown-tomentose below, floccose to subglabrous above; involucres 2–2.5 mm, subglabrous or glabrous; flowers 1.5–2(–2.5) mm; and achenes 1.8–2 mm long.
Variety lapidicola is a subshrub 0.5–0.5 dm tall, with leaf blades elliptic, 3–7(–8) mm long × 1–4 mm wide, densely reddish-brown-tomentose below, tomentose to floccose above; involucres 2.5–3.5 mm, floccose to subglabrous; flowers (1.5–)2–3.5 mm; and achenes 2.5–3 mm long.
Map 5, var. arceuthinum and var. phoeniceum. Both of these are rare, known only from a very few locations in eastern Nevada and western Utah. Varieties laxiflorum, simpsonii, and to a lesser extent lapidicola are also prevalent in this region. Variety arceuthinum (Juniper Mountain wild buckwheat) (specimen images) is known from a scant 5 specimens in the Mahogany Mountains of Lincoln County, Nevada and Iron County, Utah. Variety phoeniceum (Scarlet wild buckwheat) (specimen images) is apparently known from only 3 specimens collected in Millard and Beaver counties, Utah.
Both are short, compact subshrubs, under 10 cm tall. Both have very small, narrowly linear leaf blades, 4–8 mm long and ≤ 1.2 mm wide, densely white-tomentose below and sparsely floccose or glabrous and green above, with revolute margins. The differences are subtle: (1) var. arceuthinum is generally 5–7 cm tall with a spreading caudex, while var. phoeniceum is only 2–4 cm tall, generally without a caudex; (2) var. arceuthinum has glabrous involucres, while var. phoeniceum has floccose to subglabrous involucres. With so few specimens available, and the differences so minor, are these really distinct taxa? More fieldwork needed, I think.
Map 6, var. corymbosoides, var. johnstonii, and var. lacus-ursi. These three varieties occur only in the Transverse ranges of southern California. Of the more widespread varieties, only var. simpsonii may also occur in this area. It differs from these three in having flowering stems and inflorescence branches that are generally tomentose to woolly-hairy (vs. generally glabrous in var. corymbosoides, var. johnstonii, and var. lacus-ursi).
Variety lacus-ursi (Bear lake wild buckwheat) (specimen images) consists of subshrubs about 1.5–2 dm tall, with cream-colored flowers 2.0–2.5 mm long. Its leaves are narrowly elliptic, densely white-tomentose below and glabrous or nearly so above, with the margins usually revolute. It is known only from clayey outcrops in Bear Valley in the San Bernardino Mountains.
Variety johnstonii (Johnston’s or San Gabriel Mountains wild buckwheat) (specimen images) consists of decumbent, spreading subshrubs, less than 1.5 dm tall, with white to reddish flowers mostly 3–3.5 mm long. Its leaves are elliptic to obovate, densely whitish-brown-tomentose below and floccose to subglabrous above, with the margins usually not revolute. It occurs in montane conifer woodlands and was initially known only from high elevations in the San Gabriel Mountains, but has since been found in the San Bernardino Mountains as well.
Variety corymbosoides (San Bernardino wild buckwheat) (specimen images) consists of larger, rounded to spreading shrubs, 3–6 dm tall, with white to reddish flowers 2.0–2.5 mm long. As in var. johnstonii, its leaves are elliptic to obovate, densely whitish-brown-tomentose below and floccose to subglabrous above, with the margins usually not revolute. It occurs in chaparral and in oak and conifer woodlands in both the San Bernardino Mountains and San Gabriel Mountains.
Map 7, All varieties, with (very) approximate range boundaries.
As of this writing, there are no observations in iNaturalist for the rarest varieties of Eriogonum microtheca: vars. arceuthinum, phoeniceum, lacus-ursi, corymbosoides, and johnstonii. These present great opportunities for Nevada/Utah and SoCal botanists to document these taxa with photographs from the field!
When photographing these plants, try to capture the following details: 1) stem hairs: abundance, texture, and color; 2) perianth color; 3) leaf blades: hairiness above and below, margins revolute or not, length (measure); 4) plant height (measure).
All photos, maps, and text are copyright Tim Messick 2015-2023, except where other sources are given credit. All rights reserved. No copying or modification without written permission. Links are welcome. Thanks!