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| desert five-spot, Eremalche rotundifolia, in Hawk Canyon on 28 March 2011. Left: flower. Right: calyx in fruit, with just two seeds left. | ||
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| Borrego Mountain as seen from the curve just beyond mile 8.5 on the portion of S22 known as the Montezuma Grade, on 6 December 2005, on an especially clear day. See Views From the Montezuma Grade of S22 for identifications of other features in the photograph. | ||
Introduction
Procedure For Compiling the Checklist
Analysis of the Checklist
Important Caveats
Checklist
Flora of Borrego Mountain
The checklist here has been updated on 10 January 2019 from eight additional field surveys; a new voucher search; and inclusion of iNaturalist observations. The text has not yet been updated.
This checklist is a start at a flora of Borrego Mountain, compiled from surveys of six different areas in 2011 and one area in 2016, and voucher records.
For this checklist, the Borrego Mountain area is defined as including San Felipe Wash as its northern boundary; SR78 as its southern boundary, with the short section of Borrego Springs Road as its western boundary, and the longitude of Benson Lake as its eastern boundary. This boundary is shown in Fig. 1, along with the locations of our surveys and of vouchers.
Fig. 1. Boundary of the Borrego Mountain Floral Area (heavy black line), and locations of the five survey areas (as of 28 March 2011, the labeled lines and cross) and vouchers (blue diamonds). Two more recent survey areas are not yet shown on this map.
The flora of Borrego Mountain has additional interest because it has some aspects of being an "Island Flora" since it is an isolated (small) range not connected to any of the surrounding mountain ranges. Borrego Mountain is surrounded by Badlands and alluvial sediment. Hence the species that live only in rugged regions, and that cannot live in alluvial areas, can't easily get here. If they do, but not too frequently, and/or their population doesn't quickly go to fairly large numbers, they can suffer extinction due to normal population fluctuations, just like a typical island flora.
For beautiful photographs of many of the species found here, and of the scenery, see the following pages by Fred Melgert and Carla Hoegen:
- Borrego Mountain Wash loop
- The Slot
- Slot Canyon Trail
- The Slot / Cascade Loop
- West Butte The Slot Loop
- Hawk Canyon Loop
- Hawk Canyon Loop 2
- Blow Sand Canyon Loop
For photographs of more than 75% of the species seen in the 7 December 2018 survey, see the iNaturalist observations from Terry Hunefeld (123 observations of 57 taxa); Don Rideout (77 observations of 52 taxa); and Birgit Knorr (53 observations of 36 taxa).
For photographs of the species seen in the 28 December 2018 survey, see the iNaturalist observations from Kate Harper, 78 observations of 64 taxa.
For photographs of the species seen in the 26 December 2018 survey by Fred Melgert and Carla Hoegen, see their iNaturalist observations, 101 observations of 36 taxa.
Procedure For Compiling The Checklist
The Checklist was compiled from field work done by the authors and from online vouchers.
Field Surveys
Seven different locations were surveyed; the locations of the first five are shown in Fig. 1, and the parameters of all the surveys for each are given in Table 1. Three of those locations were surveyed twice; the other two were surveyed a single time.
The survey areas were:
- SR78. Two nearby areas were surveyed, at the northwest corner of SR78 and Buttes Pass Road, and the southwest corner of SR78 and the access road to Harper Canyon. These were "accidental" survey areas, done first while waiting for everyone to show up, and then because we weren't allowed into the Borrego Mountain area for about an hour while unexploded ordinance was being blown up.
- West. This survey of the West Butte area is the 4 mile route described in Schad. We first surveyed the vicinity of the parking area at the top of The Slot. We then hiked to the peak of the West Butte, and took the use trail to the west to a tributary of Borrego Mountain Wash. This tributary was one of the richest areas of that survey. We followed that tributary to the junction with Borrego Mountain Wash, then surveyed up Borrego Mountain Wash through The Slot back to the cars.
In the second survey of this area, we did the route in reverse.
- West Area #2. This survey of the West Butte area is Fred Melgert and Carla Hoegen's The Slot / Cascade Loop. See their page for a map of that hike.
- Hawk Canyon. This delightful canyon was surveyed up to just past the farthest point that cars can travel, where the bottom begins to be overgrown with shrubs. We surveyed counterclockwise on the first survey, and again reversed it on the second survey.
- North base of West Butte. We had intended to survey the area of San Felipe Wash, at its junction with Buttes Pass Road. But that area was so depauperate on 11 January 2011 that we instead drove west to the north base of the West Butte, and surveyed a small loop in that area.
On the return trip on 28 March 2011, we had time to survey only about one fourth of the area surveyed on 11 January 2011.
- Goat. We drove the Goat Trail to its highest point, then parked and surveyed to the east, into the top portion of Blow Sand Canyon.
- San Felipe Creek / Blowsand Canyon. We mostly car surveyed along San Felipe Creek from Borrego Springs road to Blowsand Canyon, and then surveyed up the lower part of Blowsand Canyon by foot. (The route is not yet shown in Fig. 1.)
A total of 50 hours of field surveys were done on six days in January - April 2011, plus one day on 15 December 2016, by the following people:
- 6 January 2011, West Butte, by Tom Chester, Mike Crouse, James Dillane, with RT and Shaun Hawke and Bill Sullivan helping with a portion of the survey.
- 11 January 2011, Hawk Canyon, north base of Borrego Mountain, by Tom Chester, Mike Crouse, Pam Pallette, with RT and Shaun Hawke helping with a portion of the survey.
- 3 February 2011, Goat Trail, by Tom Chester, Mike Crouse, Vince Balch, and James Dillane.
- 8 March 2011, West Butte and SR78, by Tom Chester, Mike Crouse, Vince Balch, and Kate Harper.
- 28 March 2011, Hawk Canyon, north base of Borrego Mountain, by Tom Chester and Kate Harper.
- 3 April 2011, San Felipe Creek / Blowsand Canyon, by Tom Chester, Vince Balch, Mike Crouse, Kate Harper, and Dylan Neubaeur.
- 15 December 2016, The Slot / Cascade Loop, by Tom Chester and Nancy Accola.
The authors of this page are those that contributed at least 20% of the total survey time.
The parameters of the survey areas done in January - March 2011 are given in Table 1; the table does not yet includes results of the two later surveys.
Table 1. Characteristics of the Survey Areas and Number of Taxa Found
| Area | Distance (miles) | Survey Time (hours) | # of People | # of Taxa |
|---|---|---|---|---|
| SR78 | 0.1 | 1 | 4 | 42 |
| West | 4.0 | 14 | 4-6 | 102 |
| Hawk | 0.5 | 10.5 | 2-5 | 88 |
| North | 0.8 | 4 | 2-5 | 76 |
| Goat | 1.9 | 4.5 | 4 | 72 |
A total of 128 taxa were found in the union of all the surveys, 121 native and 7 non-native.
Table 2 gives a breakdown of how many taxa were found in 1, 2, 3, 4 or all 5 survey areas.
Table 2. Number Of Taxa Found, Separated By The Number Of Survey Areas Containing Each Taxon
| # Survey Areas | # Native Taxa | # Non-Native Taxa |
|---|---|---|
| 1 | 32 | 3 |
| 2 | 18 | 0 |
| 3 | 19 | 1 |
| 4 | 24 | 2 |
| 5 | 28 | 1 |
| All | 121 | 7 |
As expected, the largest number of taxa were found in only a single survey area. However, instead of the usual continuous decline to smaller numbers with larger number of survey areas, the number of native taxa actually increases moderately toward ones found in all five survey areas. This most likely indicates a low variability in the types of habitats here. The histogram is also affected by the large difference in size between the surveyed areas, which favors preferentially finding the widespread species.
Voucher Records
The vouchers come from a search on 5 January 2011 and on 31 March 2011 of the Consortium of California Herbaria.
On 5 January 2011, the Consortium records were searched for San Diego County specimens found between latitudes of 33.15 and 33.24° and longitudes of -116.24 and -116.14°. The localities were examined and vouchers not in the Borrego Mountain area as defined above were removed.
On 31 March 2011, the Consortium records were searched for San Diego County specimens with the words Borrego and mountain in their locality field. This returned 1,904 records, which were almost entirely not in the Borrego Mountain area (with such localities as Anza-Borrego Desert State Park, Laguna Mountains Region). Only 99 vouchers were not georeferenced. Only those vouchers were examined, as a complement to the previous coordinate search. Of those, six were actually in the Borrego Mountain area.
Two vouchers were rejected as being incorrectly determined:
- CHSC96397. Its determination of Hazardia squarrosa is incorrect if it was actually collected in its locality of Borrego Mountain Wash between the end of The Slot and the jeep road leading up out of the wash, since that is where we found Isocoma acradenia. Hazardia squarrosa is not found east of the crest of the Laguna Mountains in this area. The closest voucher from there is 21 miles west of Borrego Mountain.
- RSA599300. Its determination of Ditaxis serrata is incorrect since that species does not occur in San Diego County according to the 2006 Checklist of the Vascular Plants of San Diego County by Rebman and Simpson. Plants that were previously referred to D. serrata are now classified as D. neomexicana.
The final list contained 120 vouchers of 75 distinct taxa. Bill Sullivan was the dominant collector by far, with 52 vouchers, 43% of the total. Larry Hendrickson, Kim Marsden, L. Louise Jee contributed 18 vouchers, 15% of the total. Joe Barth collected 10 vouchers, 8% of the total. The remaining 40 vouchers were collected by 13 different groups.
Total Checklist
This section has not yet been updated to include results from the last two surveys.
The total checklist present below contains 140 taxa. Of those 140 taxa, 63 were both found in our survey and have vouchers from this area; 65 taxa were found only in our surveys, and 12 taxa were found only from vouchers.
The 12 taxa found only in vouchers were mostly found in areas we did not survey, especially the San Felipe Wash and lower Blow Sand Canyon / Wash area.
Analysis of the Checklist
This analysis was done on the checklist as of 30 March 2011, with names given in the Jepson Manual first edition system. It has not been redone with the results from the later surveys.
Species not found here
Since this flora is similar to an island flora, it is of interest to see what species are not found here, that are common in the surrounding area. The most common species found in our other Borrego Desert surveys, that are not found here, are given in Table 3.Table 3. Most Common Borrego Desert species not found at Borrego Mountain
| # Other Survey Areas | Scientific Name | Common Name |
|---|---|---|
| 51 | Opuntia ganderi | Gander's cholla |
| 50 | Opuntia basilaris var. basilaris | beavertail cactus |
| 48 | Ferocactus cylindraceus | California barrel cactus |
| 38 | Trixis californica var. californica | California trixis |
| 37 | Cheilanthes parryi | woolly lipfern |
| 36 | Adenophyllum porophylloides | San Felipe dogweed |
| 34 | Salvia columbariae | chia |
Interestingly, both ferns and cactus are on that list. The flora of Borrego Mountain has no ferns at all, and is missing two of the most widespread and abundant cactus species, Ferocactus cylindraceus and Opuntia basilaris. (Opuntia ganderi isn't expected here since it prefers wetter, cooler areas. It is replaced here by O. echinocarpa. However, we probably observed one plant in San Felipe Creek that was a wash-down from higher elevations. That isn't included in the checklist since it is hard to be certain about the determination of a single plant, and if it is O. ganderi, it is almost surely a waif.)
Species of which only a single plant was found
It is also interesting to see the somewhat-numerous species of which we found only one single plant in a single survey. They even include a single Opuntia bigelovii, which almost never comes as a single plant! In this case, it was because of the small area surveyed at SR78. There were numerous plants along Buttes Pass Road to the north, but that area wasn't included in any survey.Just as amazing was the single plant of Erodium cicutarium we found at the parking area for The Slot. This was either a waif, from cars or hikers, or the earliest plant of an invasion to come there. It is very heartening to see the abundance of the native Erodium texanum on every survey here, along with the absence of E. cicutarium.
Interesting species pairs
The numbers in the checklist below look like an error was made for the determination of the Phacelia crenulata varieties. We found only var. minutiflora everywhere except in the West survey, where all we found was var. ambigua! But those varieties are very distinct, and no error was made.Diversity of species here
The Borrego Mountain Area is currently the second most depauperate area in Tom's database. Table 4 gives the ratio of the number of native taxa found to that predicted for the most depauperate areas. The prediction is from a power law best fit to the number of taxa versus area for the areas for all southern California in Tom's database (number of taxa = 128 * area in square miles ^ 0.28).As expected, low desert regions have lower species counts than island floras due to their much more extreme climate for heat, cold, and the lack of rainfall. Although the number of taxa in the Checklist will undoubtedly increase as more of Borrego Mountain is surveyed, it is unlikely to improve its ranking much on this list for those reasons.
Borrego Mountain is about twice as diverse as the Borrego Badlands since it has more habitats than the Badlands, including additional rock types. The Borrego Badlands consist entirely of young, mostly saline, sedimentary rock. That rock is also found at Borrego Mountain, where it is accompanied by ancient metamorphic bedrock, with much more vertical relief than is found in the Badlands rock formations.
Two other species-challenged areas are represented in Table 4:
- The tree canopies in the Pine Belt of our local mountains deprive the forest floor of sunlight, creating large areas that consist of only a handful of tree species. The high elevations of the Pine Belt also have an extreme climate for cold, and for a short growing season.
- Island floras are depauperate because it is difficult for many mainland species to reach islands; only species capable of dispersal across bodies of water can populate islands. In addition, the small area of islands causes low numbers for some species, which can then go extinct simply from normal population fluctuations from year to year.
Table 4. Ratio Of The Number Of Native Taxa Found To That Predicted From The Species / Area Relationship For southern California.
| Ratio | Area |
|---|---|
| 0.23 | Borrego Badlands |
| 0.45 | Borrego Mountain |
| 0.50 | northeast Vallecito Mountains |
| 0.58 | San Clemente Island |
| 0.59 | Coyote Mountain area, Borrego Springs |
| 0.59 | SnGb Pine Belt (Johnston) |
| 0.76 | Starfish cove / Alma Canyon / Wash |
| 0.78 | high desert mtns |
Of course, depauperate does not mean there aren't interesting species here, or that this is not a beautiful area! It only means it has a low number of different species.
Some of the beautiful flowers in this area are:
- the big beautiful blooms of Xylorhiza orcuttii;
- hillsides of desert five-spot, Eremalche rotundifolia; ghost flower, Mohavea confertiflora, including a hill with a single plant with 88 flowers open at once, and Phacelia crenulata var. ambigua.
- fields of Lupinus arizonicus and Monoptilon bellioides.
And there aren't many places where one can find plants of three Chorizanthe species, C. brevicornu, C. corrugata, and C. rigida, growing within inches of each other. Depauperate dry, saline areas like here are the only place that dead man's fingers, Calandrinia ambigua, grows in the Borrego Desert.
Important Caveats
As is the case for all floras, this one is undoubtedly incomplete. It is clear from Fig. 1 that many areas of Borrego Mountain have not yet been surveyed, including the entire East Butte, the lower part of Blow Sand Canyon and Borrego Mountain Wash, several drainages on the northwest side of West Butte, and most of the San Felipe Wash below Borrego Springs Road.
In addition, it is likely that even the surveyed areas are incomplete. Table 5 gives the number of taxa found in the three areas that were surveyed twice, 2.0 to 2.5 months apart.
Table 5. Number of Taxa Found in Repeated Surveys.
| Survey Area | Date | # Taxa each Survey | Cumulative # Taxa total from all surveys |
|---|---|---|---|
| West | 6 January 2011 | 85 | 85 |
| West | 8 March 2011 | 94 | 102 |
| Hawk | 11 January 2011 | 68 | 68 |
| Hawk | 28 March 2011 | 84 | 88 |
| North | 11 January 2011 | 64 | 64 |
| North | 28 March 2011 | 61* | 76 |
* The survey of the North base of Borrego Mountain was of a much shorter distance on 28 March 2011, yet it still added 12 species to its flora.
It is quite clear from Table 5 that it is unlikely we've recorded all the species in each of those areas. Surveys at different times of year, and in different years, find different species.
Finally, the numbers of some annual species may be too low in some cases. Since our surveys were all done in a single year, they couldn't reflect the proper abundance of annuals that did not germinate well this year. For example, we found Oligomeris linifolia in only one location in Hawk Canyon, where there were over 100 dead plants from a previous year, and only one live one this year. Every good year is different, due to the different germination requirements of different species.
Checklist for Borrego Mountain
The checklist here has been updated on 10 January 2019 from eight additional field surveys; a new voucher search; and inclusion of iNaturalist observations. The text has not yet been updated.
See:
- Notes on the Scientific Names Used At This Site and
- Information about the order in which the species are presented, and the links from the Scientific Name and Common Name.
An asterisk before the common name indicates a non-native species.
The column with header BW
links to the photo gallery page for each species at Fred Melgert and Carla Hoegen's BorregoWildflowers site.
The column #V gives the number of vouchers from this area for each taxon.
The column #Pls gives an estimate of the minimum number of plants for each taxon observed in the union of all survey areas, up to a maximum of 99 plants. If there is a V in this column, it indicates a species that was vouchered, but not yet seen by us. If there is an iN in that column, there is an iNaturalist observations of species we haven't yet seen and that hasn't been vouchered.
For an older checklist that has the results for different areas presented separately, see Detailed Checklist.
Version for printing, without lines and other text on this page: html (5 pages); pdf Clickbook booklet (2 double-sided pages); or a pdf Clickbook booklet condensed to fit on 1 double-sided page by removing the overall header and the clade headers. (See printing instructions for an explanation of these options)
We thank Shaun Hawke for help with part of the 1/6/11 and 1/11/11 surveys, and RT Hawke for help with both those surveys; Bill Sullivan for help with part of the 1/6/11 survey; Pam Pallette for help with the 1/11/11 survey; Dylan Neubauer for help with the 4/3/11 survey; Birgit Knorr for help with the 12/7/18 survey; Beth Cobb for help with the 12/28/18 survey; and Jim Roberts for help with the 1/7/19 survey.
Voucher data provided by the participants of the Consortium of California Herbaria (ucjeps.berkeley.edu/consortium/)