Plant Species of the Borrego Desert: Liliaceae: Hesperocallis undulata, desert lily


Table of Contents

Origin and Meaning of Name, and Family Placement
Distinguishing Characteristics and Similar Species
Pictures of Young Plants, Mature Plants, and Dead Plants
Habitat, Distribution and Abundance
References


Origin and Meaning of Name, and Family Placement

The genus name Hesperocallis is from the Greek hesperos, "west," and kallos, "beauty," and means "western beauty" (Charters 2009). It was named by Asa Gray in 1867, who thought this species was related to Hemerocallis, the common day lily that is native to the Eastern Hemisphere. The name suggests that affinity, along with the far western, instead of eastern habitat (Gray 1867, quoted in Pires 2004). The specific epithet undulata means wavy-margined, referring to the usual wavy margins of the leaves (Charters 2009).

Hesperocallis undulata is the only species in its genus. It was named from a specimen collected by J.G. Cooper, from Jessup Rapids, Arizona. The specimen was collected as part of the U.S.-Mexican Boundary Survey from 1860-1861 (Abrams 1955).

There has been considerable debate about the plant family of this species. Such debate often occurs for genera that have only one species, since such species diverged a long time ago evolutionarily from their closest relatives. Without sister species, it is not clear what characteristics are those of the genus and what are those of the species. This hampers the inference of what characteristics are those of its family.

Hesperocallis has been placed in the day lily family Hemerocallidaceae; in the Funkiaceae = Hostaceae Family; in the Agave family Agavaceae; in the narrowly-defined lily family, Liliaceae; or in its own family Hesperocallaceae. In turn, these families have sometimes been placed in the expanded Liliaceae or Asperagaceae families.

The molecular data from two specimens from Anza-Borrego Desert State Park show that this species is most closely related to Agave, the namesake of the Agavaceae family (Pires et al 2004).

Distinguishing Characteristics and Similar Species

Fig. 1. The picture above (without the labels) is a crop of a beautiful bigger picture by Michael Charters, taken in the eastern part of the Mojave National Preserve (see his full page on desert lily with more information)

Fig. 2. Picture of a desert lily leaf taken in Palm Wash, near the Calcite Mine Road, on 19 January 2009.

Distinguishing Characteristics:

Similar species. There are no look-alike species. Species similar in habit have much different leaves, or their flowers are either different colors, have a different number of petals, or are much different in size and spacing. As of 21 January 2009, no pictures at Calphotos labeled as Hesperocallis undulata are misidentified.

Dune primrose, Oenothera deltoides, has a somewhat similar white flower on a similar-sized flower stalk, but its flower has four petals and its leaves are much shorter and wider.

If you have ever confused another species with desert lily, please let me know and I'll add it to this section.

Pictures of Young Plants, Mature Plants, and Dead Plants

Young Plant Pictures

When desert lily is emerging from the ground, it can appear quite different, depending on whether it is emerging from sand or from gravelly areas.

The next two pictures show young plants emerging from sand:

Fig. 3. A single desert lily leaf emerging from sand. Picture taken on a broad flat saddle south of Seventeen Palms in the Borrego Badlands on 19 December 2008.

Fig. 4. A young desert lily plant with three leaves emerging from sand. Picture taken on a broad flat saddle south of Seventeen Palms in the Borrego Badlands on 19 December 2008.

The following pictures show young plants emerging from broken-up rock. The leaves have to be more substantial to push through rocks, and hence are thicker, and more clumped as they push up, giving a quite different appearance. Two of the emerging plants shown below were photographed by James Dillane on 2 January 2009, and both he and I could not believe these could be desert lily. As a result, we made a special trip on 19 January 2009 to relocate these plants, and were dumbfounded that they became normal-looking desert lily plants. We also were able to find, in a nearby area, some additional plants that had just emerged, which resembled the plants of 2 January 2009. One picture of those plants is shown below.

Fig. 5. A young desert lily plant with three leaves emerging from a hard soil made of broken-up rock and cemented sand grains. Picture taken on a hill of conglomerate on the use trail to get around the waterfall in the upper portion of the South Fork of Palm Wash, on 19 January 2009.

Fig. 6. A clump of two or three desert lily plants emerging from hard ground. Picture taken by James Dillane on a hill of broken limestone rock on the use trail to get around the waterfall in the upper portion of the South Fork of Palm Wash, on 2 January 2009.

Fig. 7. Picture taken on the same hill of broken limestone rock on the use trail to get around the waterfall in the upper portion of the South Fork of Palm Wash, on 19 January 2009.

Fig. 8. Picture taken by James Dillane on a hill of conglomerate in the upper portion of the South Fork of Palm Wash, on 2 January 2009. The six plants on the right look very different from the young plants growing in sand since they have just emerged from the rocky soil and still retain their subterranean shape. The two plants on the left have developed into normal-looking desert lilies, since they emerged from the rocky soil earlier. Note that they each consist of three equal-length leaves, which must have been tightly bunched earlier as in the plants at right. Desert lily is a monocot, which typically have parts in threes.


Picture taken on the same hill of conglomerate in the upper portion of the South Fork of Palm Wash, on 19 January 2009.

The plants in the last two pictures are the same, as you can tell by matching the rocks, and noting that the same small gully is present in both pictures. The pictures were taken at somewhat different angles.

Mature Plant Pictures

The next two pictures are of the same plant, and show the flower stalk emerging. In the second picture I've pulled back the leaf covering the bud.


Picture taken on a hill of conglomerate on the use trail to get around the waterfall in the upper portion of the South Fork of Palm Wash, on 19 January 2009.


Picture taken on a hill of conglomerate on the use trail to get around the waterfall in the upper portion of the South Fork of Palm Wash, on 19 January 2009.


Picture taken on a flat area along the upper Calcite Mine Road on 21 February 2008.

Mature leaves are usually wavy, but can sometimes have straight edges. The following pictures were taken in Palm Wash, near the Calcite Mine Road, on 19 January 2009, of two nearby plants.

Dead Plant Pictures

Note that only the three lowest flowers developed seeds on this plant. All pictures were taken in Clark Valley just west of Clark Lake on 9 December 2009.

Habitat, Distribution and Abundance

Desert lily is one of the most common species in the Borrego Desert, being found in 7 of the 24 surveyed areas (as of 2009). This abundance is a bit surprising, since native Americans ate the bulbs. Perhaps native Americans spread the seeds to increase the number of this species; perhaps the bulbs are buried deep enough to discourage easy harvest; or perhaps the bulbs didn't taste good enough to make them a primary food source.

Desert lily grows on dry sandy flats and washes, on hills made of loose material forming gentle slopes, and even in sandstone or sandy conglomerate. Examples of the different habitats are shown in the pictures above.

Some locations of dry sandy flats and washes with desert lily are Coyote Creek wash north of Di Giorgio Road; Desert Gardens; and flat areas in the Borrego Badlands. Location of gentle hills of loose material are the broken limestone hills above Palm Wash. See Fig. 18 below for detailed locations.

Maps of the distribution of desert lily in ABDSP are given in Fig. 18 from my locations and from iNat, as of 18 March 2020. iNat is by far the dominant source of locations, with 1,774 observations with good coordinates (161 were rejected due to poor or obscured coordinates). Fred Melgert and Carla Hoegen are by far the dominant observer, with 765 observations, 43% of the total, followed by Don Rideout with 198 observations and Terry Hunefeld with 190 observations, each with 12% of the total. No other observer has more than 4% of the total.

Fig. 18. Distribution of desert lily in ABDSP as of 18 March 2020, from 104 of my locations and 1,774 iNat observations. Locations with at least 50 desert lilies are plotted with larger symbols, 20 from my locations and 53 from iNat observations. See the text for caveats on the larger symbols.

Top: The Borrego Valley Area, the northern part of ABDSP. Bottom: The Vallecito / Carrizo Valley Area, the southern part of ABDSP.

See also larger versions of these maps: northernmost; northern middle; southern middle; southernmost.

In Fig. 18, some of those larger symbols are from the same population, and hence overlapping large symbols do not necessarily mean more than 50 desert lilies in an area. An example is the area southwest of Vallecito County Park, where nine iNat observations from the population were each tagged with being part of the same large population. That can happen in my surveys, too, when an area was surveyed with differing starting points.

Note that most iNat observations do not have associated abundances, and half of my data has not yet been digitized, so there are almost surely more locations with at least 50 desert lilies. But we do encounter many locations that have just one or a few desert lilies, or scattered numbers that do not add up to 50 plants, such as in the Horse Camp Area in the northeast Borrego Valley area.

There are so many iNat observations that these maps are very useful to identify where desert lily is common, and where it is not. Some of the places where it is not yet found might just be unexplored, but many of the places where it is not found are almost surely real.

However, the absence of many points in an area should not be taken as an indication that desert lilies are scarce in an area without knowing how well surveyed that area is, even from a map made with over 1,800 observations. Some of us surveyed an area in the southernmost end of ABDSP that had only a small number of observations in the Volcanic Hills area as of 10 March 2020. Don Rideout and I; Walt Fidler; Fred Melgert and Carla Hoegen; and Birgit Knorr separately made surveys there to record desert lilies. Altogether, we found roughly 1,000 plants and producing a dramatic increase in the number of records for it there! Compare the 10 March 2020 map of that area with the 18 March 2020 map of that area. The two linked maps are the same size, so if you open them in separate aligned windows you can blink them to see the increase.

This example shows pretty strongly that the southernmost end of the park is not well covered, since if a showy plant like desert lily is vastly under-recorded here, all species are likely to be under-recorded here as well.

In Fig. 18, one can easily see the known sandy areas in ABDSP, such as the sandy areas near Coyote Creek; the Borrego Dunes by the Borrego Dump; the San Felipe Creek area dunes; the dune areas in Clark Valley; and the sandy areas in the Vallecito Creek Area and the sandy washes draining into Vallecito Creek.

The other dense concentrations shown in Fig. 18 are the Badlands sandstone formation.

Desert lily clearly does not like alluvial plains, such as the Upper Clark Valley area, Yaqui Meadows and the alluvial plains on the west side of Borrego Springs.

Desert lily is widespread in both the Mojave and Sonoran Deserts. The following map shows the distribution of vouchers with coordinates from the Consortium of California Herbaria made in 2009 (only California locations are plotted):


Data provided by the participants of the Consortium of California Herbaria (ucjeps.berkeley.edu/consortium/).

The distribution of vouchers with coordinates from SEINet from 2009 is shown in the following map:

References

Abrams, Leroy 1955, Illustrated Flora of the Pacific States, Vol. 1, 411.

Charters, Michael 2009, California Plant Names: Latin and Greek Meanings and Derivations, accessed 21 January 2009.

Gray, Asa 1867, Hesperocallis, Nov. Gen. Liliacearum. Proceedings of the American Academy of Arts and Sciences 7:390-391.

Pires, J. Chris, et al 2004, Madrono, 51:307.


Go to:


Copyright © 2009-2020 by Tom Chester.
Commercial rights reserved. Permission is granted to reproduce any or all of this page for individual or non-profit institutional internal use as long as credit is given to me at this source:
http://tchester.org/bd/species/agavaceae/hesperocallis_undulata.html
Comments and feedback: Tom Chester
Updated 18 March 2020.