Flora of Borrego Mountain

desert five-spot, Eremalche rotundifolia, in Hawk Canyon on 28 March 2011. Left: flower. Right: calyx in fruit, with just two seeds left.
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.

Procedure For Compiling the Checklist
Analysis of the Checklist
Important Caveats

Flora of Borrego Mountain

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:

See also their overview map showing the routes for each of the above hikes. Borrego Mountain is in the southernmost portion of their map; zoom in there to see their hikes at Borrego Mountain.

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:

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:

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

AreaDistance (miles)Survey Time (hours)# of People# of Taxa

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

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:

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.

Three of the taxa found only in vouchers are very similar to species we found: Loeseliastrum schottii, Eriogonum reniforme, and Schismus arabicus from vouchers; Loeseliastrum matthewsii, Eriogonum thomasii, and Schismus barbatus from our surveys. We suspect the first two voucher species are misdetermined, and will check those vouchers when we get the chance. See also Loeseliastrum matthewsii and L. schottii.

We didn't bother to distinguish the two Schismus species in our surveys, but all the Schismus plants we have checked in the Borrego Desert have been S. barbatus. That, of course, does not necessarily imply that the plants here are also S. barbatus, but that is the way to bet. We'll check some plants in the future to be sure, as well as that voucher.

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 AreasScientific NameCommon Name
51Opuntia ganderiGander's cholla
50Opuntia basilaris var. basilarisbeavertail cactus
48Ferocactus cylindraceusCalifornia barrel cactus
38Trixis californica var. californicaCalifornia trixis
37Cheilanthes parryiwoolly lipfern
36Adenophyllum porophylloidesSan Felipe dogweed
34Salvia columbariaechia

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:

Table 4. Ratio Of The Number Of Native Taxa Found To That Predicted From The Species / Area Relationship For southern California.

0.23Borrego Badlands
0.45Borrego Mountain
0.50northeast Vallecito Mountains
0.58San Clemente Island
0.59Coyote Mountain area, Borrego Springs
0.59SnGb Pine Belt (Johnston)
0.76Starfish cove / Alma Canyon / Wash
0.78high 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:

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 AreaDate# Taxa each SurveyCumulative # Taxa total from all surveys
West6 January 20118585
West8 March 201194102
Hawk11 January 20116868
Hawk28 March 20118488
North11 January 20116464
North28 March 201161*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

This checklist has been updated to include all surveys through 12/15/16, and put in the 2012 Jepson Manual Second Edition system.


An asterisk before the common name indicates a non-native species.

The column #V gives the number of vouchers from this area for each taxon.

The column #Pls gives an estimaet of the minimum number of plants for each taxon observed in the union of all survey areas, up to a maximum of 99 plants.

For a 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 (4 pages) or pdf Clickbook booklet (1 double-sided page). (See printing instructions for an explanation of these options)

#FamScientific Name(*)Common Name#V#Pls
1EphEphedra californicadesert tea 3
2AmaTidestromia suffruticosa var. oblongifoliaArizona honeysweet 3
3ApoAsclepias subulatarush milkweed122
4ApoFunastrum hirtellumrambling milkweed125
5ApoPilostyles thurberiThurber's pilostyles1 
6AstAmbrosia dumosaburroweed399
7AstAmbrosia salsola var. salsolacheesebush 99
8AstBebbia juncea var. asperasweetbush299
9AstCalycoseris wrightiiwhite tackstem199
10AstChaenactis carphoclinia var. carphocliniapebble pincushion 99
11AstChaenactis stevioidesdesert pincushion199
12AstDicoria canescensdesert dicoria 99
13AstEncelia farinosabrittlebush499
14AstEncelia frutescensbutton encelia199
15AstEricameria paniculatablackbanded rabbitbrush12
16AstGeraea canescenshairy desert-sunflower299
17AstIsocoma acradenia var. acradeniaalkali goldenbush 50
18AstIsocoma acradenia var. eremophilasolitary-leaved alkali goldenbush 10
19AstLogfia depressadwarf filago 30
20AstLogfia filaginoidesCalifornia filago 99
21AstMalacothrix glabratadesert dandelion299
22AstMonoptilon bellioidesdesert star199
23AstPalafoxia arida var. aridaSpanish needle399
24AstPectis papposa var. papposachinch-weed28
25AstPerityle emoryiEmory's rock-daisy199
26AstPeucephyllum schottiipygmy-cedar 21
27AstPleurocoronis plurisetaarrow-leaf 77
28AstPsathyrotes ramosissimaturtleback 2
29AstRafinesquia neomexicanadesert chicory 41
30AstSenecio mohavensisMojave ragwort299
31AstStephanomeria exigua ssp. exiguaslender wreathplant195
32AstStephanomeria pauciflorawire-lettuce 40
33AstTrichoptilium incisumyellow-head 99
34AstXylorhiza orcuttiiOrcutt's woody-aster 2
35BigChilopsis linearis ssp. arcuatadesert-willow26
36BorAmsinckia tessellata var. tessellatabristly fiddleneck 1
37BorCryptantha angustifolianarrow-leaved cryptantha499
38BorCryptantha barbigera var. barbigerabearded cryptantha 99
39BorCryptantha maritimaGuadalupe cryptantha199
40BorCryptantha micrantha var. micranthared-root cryptantha1 
41BorCryptantha pterocaryawing-nut cryptantha 1
42BorEmmenanthe penduliflora var. penduliflorawhispering bells 99
43BorEucrypta micranthadesert eucrypta16
44BorHeliotropium curassavicum var. oculatumseaside heliotrope1 
45BorPectocarya heterocarpachuckwalla pectocarya 3
46BorPectocarya platycarpabroad-fruited combseed 30
47BorPectocarya recurvatacurvenut combseed 99
48BorPhacelia crenulata var. ambiguaheliotrope phacelia 99
49BorPhacelia crenulata var. minutifloralittle-flowered heliotrope phacelia 99
50BorPhacelia distanscommon phacelia 99
51BorPhacelia pedicellatapedicellate phacelia 6
52BorTiquilia palmeriPalmer's coldenia299
53BorTiquilia plicataplicate coldenia 99
54BraBrassica tournefortii*Sahara mustard299
55BraCaulanthus lasiophyllusCalifornia mustard 50
56BraDithyrea californicaspectacle-pod 58
57BraLepidium lasiocarpum ssp. lasiocarpumhairy-podded pepper-grass199
58BraLyrocarpa coulteriCoulter's lyrepod 5
59BraSisymbrium irio*London rocket 99
60CacCylindropuntia bigeloviiteddy-bear cholla 99
61CacCylindropuntia echinocarpasilver cholla 99
62CacFerocactus cylindraceusCalifornia barrel cactus 5
63CacMammillaria tetrancistradesert fish-hook cactus 8
64CacOpuntia basilaris var. basilarisbeavertail cactus 2
65CamNemacladus glanduliferusglandular nemacladus120
66CamNemacladus tenuis var. tenuisdesert threadplant 10
67CarAchyronychia cooperifrost mat418
68CheAtriplex canescens var. laciniataCaleb saltbush 5
69CheAtriplex hymenelytradesert holly 99
70CheAtriplex polycarpacattle saltbush 99
71CheChenopodium murale*nettle-leaved goosefoot 14
72CheSalsola tragus*Russian thistle 1
73ConCuscuta californica var. papillosapapillate dodder122
74CucCucurbita palmatacoyote melon 1
75EupChamaesyce micromeraSonoran spurge12
76EupChamaesyce polycarpasmall-seeded spurge399
77EupChamaesyce setilobastarfish (Yuma) spurge 2
78EupCroton californicusCalifornia croton299
79EupDitaxis lanceolatanarrowleaf ditaxis17
80EupDitaxis neomexicanaNew Mexico ditaxis14
81EupStillingia spinulosaannual stillingia 1
82FabAcmispon maritimus var. brevivexillusshort-bannered coastal lotus 22
83FabAcmispon strigosusstrigose lotus299
84FabAstragalus crotalariaeSalton milk-vetch 4
85FabAstragalus magdalenae var. peirsoniiPeirson's milk-vetch1 
86FabDalea mollissilky dalea115
87FabDalea mollissimadowny dalea 61
88FabLupinus arizonicusArizona lupine399
89FabOlneya tesotaironwood252
90FabProsopis glandulosa var. torreyanahoney mesquite14
91FabPsorothamnus emoryiEmory's indigo-bush199
92FabPsorothamnus schottiiindigo bush199
93FabPsorothamnus spinosussmoke tree 99
94FabSenegalia greggiicatclaw299
95FouFouquieria splendens ssp. splendensocotillo199
96GerErodium cicutarium*redstem filaree 99
97GerErodium texanumTexas filaree199
98KraKrameria bicolorwhite rhatany 99
99KraKrameria erectaPima rhatany183
100LamHyptis emoryidesert-lavender199
101LamSalvia columbariaechia 3
102LoaMentzelia involucratabracted blazing star 99
103LoaPetalonyx thurberi ssp. thurberiThurber's sandpaper-plant251
104MalEremalche rotundifoliadesert five-spot199
105MalHibiscus denudatusrock hibiscus115
106MalSphaeralcea ambigua var. ambiguaapricot mallow 2
107MonCalyptridium monandrumsand cress 1
108MonCistanthe ambiguadesert red maids 99
109NycAbronia villosa var. villosahairy sand-verbena299
110NycAllionia incarnatatrailing four o'clock 99
111NycBoerhavia wrightiiWright's spiderling 60
112NycMirabilis laevis var. retrorsaBigelow's desert four-o'clock 85
113OnaCamissoniopsis pallida ssp. pallidapale suncup 30
114OnaChylismia cardiophylla ssp. cardiophyllaheartleaf suncup136
115OnaChylismia claviformis ssp. peirsoniibrown-eyed primrose499
116OnaEremothera boothii ssp. condensataBooth's evening primrose199
117OnaEulobus californicusCalifornia suncup 99
118OnaOenothera deltoides ssp. deltoidesdune primrose 8
119OroOrobanche cooperiCooper's broomrape 99
120PapEschscholzia minutiflora ssp. minutiflorasmall-flowered poppy299
121PapEschscholzia parishiiParish's poppy 23
122PlaMohavea confertifloraghost flower199
123PlaPlantago ovatadesert plantain199
124PolAliciella latifolia ssp. latifoliabroad-leaf gilia 99
125PolGilia diegensiscoastal gilia1 
126PolGilia stellatastar gilia 3
127PolLangloisia setosissima ssp. setosissimabristly langloisia 99
128PolLoeseliastrum matthewsiidesert calico199
129PolLoeseliastrum schottiiSchott's calico1 
130PolChorizanthe brevicornu var. brevicornubrittle spineflower 99
131PolChorizanthe corrugatawrinkled spineflower 85
132PolChorizanthe rigidadevil's spineflower 99
133PolEriogonum deflexum var. deflexumflat-topped buckwheat199
134PolEriogonum inflatumdesert trumpet299
135PolEriogonum reniformekidney-leaf buckwheat1 
136PolEriogonum thomasiiThomas' buckwheat399
137PolEriogonum trichopeslittle desert trumpet 99
138PolPterostegia drymarioidesfairy bowties, threadstem 20
139ResOligomeris linifolialineleaf whitepuff 99
140SolDatura discolordesert thornapple 21
141SolNicotiana obtusifoliadesert tobacco145
142SolPhysalis crassifoliathick-leaved ground cherry229
143VisPhoradendron californicumdesert mistletoe 99
144ZygFagonia laevisCalifornia fagonia 42
145ZygLarrea tridentatacreosote bush299
146ZygTribulus terrestris*puncture-vine1 
147AgaAgave deserti var. desertidesert agave199
148AgaHesperocallis undulatadesert lily171
149PoaAristida adscensionissix-weeks three-awn399
150PoaBouteloua aristidoides var. aristidoidesneedle grama175
151PoaBromus madritensis ssp. rubens*red brome 30
152PoaFestuca bromoides*brome fescue 40
153PoaHilaria rigidabig galleta399
154PoaSchismus arabicus*Mediterranean grass1 
155PoaSchismus barbatus*Mediterranean schismus 99

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, and Nancy Accola for help with the 12/15/16 survey.

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

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Copyright © 2011-2016 by Tom Chester, Mike Crouse, Kate Harper, Vince Balch, and James Dillane.
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Last update: 17 December 2016