Flora of Sweeney Pass Area, Anza-Borrego Desert State Park

The ~200 foot high east bank of Sweeney Canyon that is just below the top of Sweeney Pass, but is unseen by motorists on S2. A short stretch of the S2 guardrail is labeled at left. One can walk to an unmarked, unsigned overlook area (labeled in the photograph) by parking along the roadside just after the last curve at the top of Sweeney Pass. Photo taken on 16 December 2012. Click on the picture for a larger version.

Botanical Highlights
Procedure For Compiling The Checklist
Species Checklist


Sweeney Pass is in the southernmost part of Anza-Borrego Desert State Park. It is a sweeping omega-shaped switchback of highway S2 in the area dividing the Jacumba Mountains from the Coyote Mountains, roughly 14 miles north of I-8. Even in dry years, one typically picks up some blooms along the highway from a good stand of Lupinus arizonicus, Arizona lupine, in the pass, along with blooms of one notable plant of Asclepias albicans, white-stemmed milkweed, just before one emerges from the top of the pass. And in good years, the bloom is stupendous!

Driving southeast, one switchbacks up from about 700 feet elevation at the Carrizo Creek crossing to 1200 feet elevation in the flattish alluvial plain leading to the Border Patrol checkpoint at the San Diego / Imperial County border, and then the town of Ocotillo (not to be confused with the off-road vehicle area of Ocotillo Wells 28 miles to the north). (See a one minute panoramic video from the top of the Pass.)

300 feet of that relief is seen on the north side of the top of Sweeney Pass at the Carrizo Badlands overview, looking down in Canyon Sin Nombre. Less visible are the ~200 feet deep canyons of Sweeney Creek to the south, which are an impressive place to botanize.

We are not very familiar at all with the immediate area of the Pass, and have only botanized a very small area along one tributary of Sweeney Canyon on part of one day in late fall, the worst time of year to observe annuals and perennials. We produced this list primarily to serve as a starting point for the flora of this area, by collecting voucher information augmented by our short survey.

This checklist is thus very incomplete.

Botanical Highlights

Even though we know little about this area, there is one major botanical highlight. As far as we know, Sweeney Canyon has the largest population of Carlowrightia arizonica, Arizona carlowrightia, in California. This species was discovered and vouchered here on 12 February 2011 by Jon P. Rebman, Mike Rood & Samantha Rebman-Rood. This was an amazing find, extending the range of this species in California by 15 miles to the south.

We specifically went to their location on 16 December 2012 to see this population, and were amazed to find at least 50 plants (we counted them!), all of which were unbrowsed. Nearly every other plant of this species that we've seen from five of the six other locations in California has been severely browsed.

Procedure For Compiling The Checklist

The Checklist was compiled from two sources:

The fieldwork was used to compile a species list, with a GPS location for at least one occurrence of every species, and to estimate abundances for each observed species. Note that the fieldwork list is extremely incomplete for annuals and perennials, since it was made from field trips at the worst-possible time of year, in late fall, which covered only a very small area of the canyon. We did not attempt to identify dead annuals except for those whose determinations were unambiguous from their remnants. The abundances for those dead annuals may be severely underestimated.

The fieldwork found 58 distinct taxa.

Vouchers were obtained from three separate searches:

Duplicate vouchers were removed, and the localities were reviewed manually to remove ones not in the target area.

That left 234 vouchers, of 124 distinct taxa. Essentially all of the vouchers were taken either along Carrizo Creek at the bottom of the pass, or along S2, with only Rebman's 28 vouchers taken from Sweeney Canyon or one of the unnamed drainages to the north of the pass.

The top collectors in this area are:

# VouchersCollector(s)
85Larry Hendrickson et al
34Joe Barth
28Jon P. Rebman et al
14Ian Cain, Emily Clayton

The union of the checklist from the fieldwork and the vouchers contains 137 taxa. Of those 137 taxa, 79 taxa were found only in the vouchers; 45 taxa were found in both the fieldwork and the vouchers; and 13 were found only from the fieldwork.

Checklist for Sweeney Pass Area

The Checklist follows the 2012 Jepson Manual Second Edition with only a few exceptions.

The Checklist is sorted first by the eight evolutionary categories (clades) used in the 2012 Second Edition Jepson Manual - lycophytes, ferns, etc., to eudicots and monocots - and then by family and scientific name. The clades are labeled in the Checklist. Note that this changes the order of presentation of the taxa from that of the 1993 First Edition.

The family name is abbreviated to the first six characters in order to save space in the table rows.

An asterisk before the Common Name indicates a non-native taxon.

The column labeled #Pls gives a minimum estimate of the number of plants from the field surveys, up to a maximum of 99 plants. The main intent of this estimate is to indicate the species for which we found very few plants.

The column labeled #V gives the number of vouchers in the Sweeney Pass area.

The scientific name is linked to the latest online Jepson Manual description for each species, which also gives the months in which each species flowers. That link also gives a map of where the species occurs in California; a plot of elevation vs. latitude for California; and a histogram of the voucher collections by month. A few species may not have working links, if their names have been updated more recently (such as Mimulus diffusus, which is still listed under M. palmeri in the online flora), or if they are reserved-judgment taxa which are listed in the entry for another taxon name.

The common name for each species in the checklist is linked to Calphotos to give pictures of most taxa. Note that the link will not always return pictures, since not every species has pictures at Calphotos, and a number of species still have their Calphotos pictures under the Jepson Manual First Edition Names.

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)

#FamilyScientific Name(*) Common Name#Pls#V
1PteridCheilanthes parryiwoolly lipfern102
2EphedrEphedra asperaMormon tea25 
3EphedrEphedra californicadesert tea 1
4AcanthCarlowrightia arizonicaArizona carlowrightia501
5AcanthJusticia californicachuparosa995
6ApocynAsclepias albicanswhite-stemmed milkweed31
7ApodanPilostyles thurberiThurber's pilostyles 7
8AsteraAdenophyllum porophylloidesSan Felipe dogweed5 
9AsteraAmbrosia dumosaburroweed992
10AsteraAmbrosia salsola var. salsolacheesebush993
11AsteraBahiopsis parishiiParish's viguiera 1
12AsteraBebbia juncea var. asperasweetbush302
13AsteraCalycoseris wrightiiwhite tackstem 1
14AsteraChaenactis carphoclinia var. carphocliniapebble pincushion991
15AsteraChaenactis stevioidesdesert pincushion 1
16AsteraEncelia farinosabrittlebush991
17AsteraEricameria paniculatablackbanded rabbitbrush 1
18AsteraEriophyllum lanosumwhite easter-bonnets 1
19AsteraGeraea canescenshairy desert-sunflower 1
20AsteraLogfia depressadwarf filago 2
21AsteraMalacothrix glabratadesert dandelion 1
22AsteraPalafoxia arida var. aridadesert needle44
23AsteraPerityle emoryiEmory's rock-daisy 1
24AsteraPeucephyllum schottiipygmy-cedar 3
25AsteraPleurocoronis plurisetaarrow-leaf33
26AsteraRafinesquia neomexicanadesert chicory 2
27AsteraSenecio mohavensisMojave ragwort 3
28AsteraStephanomeria exigua ssp. exiguaslender wreathplant 1
29AsteraStylocline intertextatangled nest-straw 1
30AsteraTrichoptilium incisumyellow-head 2
31AsteraTrixis californica var. californicaCalifornia trixis21
32BignonChilopsis linearis ssp. arcuatadesert-willow 2
33BoragiAmsinckia tessellata var. tessellatabristly fiddleneck 1
34BoragiCryptantha angustifolianarrow-leaved cryptantha54
35BoragiCryptantha maritimaGuadalupe cryptantha22
36BoragiCryptantha micrantha var. micranthared-root cryptantha 2
37BoragiEmmenanthe penduliflora var. penduliflorawhispering bells 1
38BoragiEucrypta micranthadesert eucrypta 1
39BoragiHeliotropium curassavicum var. oculatumseaside heliotrope 1
40BoragiPectocarya peninsularisBaja pectocarya 2
41BoragiPectocarya recurvatacurvenut combseed 1
42BoragiPhacelia crenulata var. minutifloralittle-flowered heliotrope phacelia 1
43BoragiPhacelia cryptanthalimestone phacelia 1
44BoragiPhacelia distanscommon phacelia 2
45BoragiPhacelia pedicellatapedicellate phacelia 1
46BoragiTiquilia plicataplicate coldenia 1
47BrassiBrassica tournefortii*Asian mustard992
48BrassiCaulanthus lasiophyllusCalifornia mustard 1
49BrassiDithyrea californicaspectacle-pod 1
50BrassiDraba cuneifoliawedge-leaved draba 1
51BrassiLepidium lasiocarpum ssp. lasiocarpumhairy-podded pepper-grass53
52BrassiSisymbrium irio*London rocket 2
53CactacCylindropuntia bigeloviiteddy-bear cholla111
54CactacCylindropuntia ganderiGander's cholla752
55CactacFerocactus cylindraceusCalifornia barrel cactus60 
56CactacMammillaria dioicaCalifornia fish-hook cactus12
57CactacMammillaria tetrancistrafish-hook cactus1 
58CactacOpuntia basilaris var. basilarisbeavertail cactus61
59CampanNemacladus rubescensdesert nemacladus 1
60ChenopAtriplex polycarpacattle saltbush101
61ConvolCuscuta denticulatadesert dodder 1
62CucurbCucurbita palmatacoyote melon 2
63EuphorAcalypha californicaCalifornia copperleaf 3
64EuphorChamaesyce micromeraSonoran spurge50 
65EuphorChamaesyce polycarpasmall-seeded spurge403
66EuphorChamaesyce setilobastarfish (Yuma) spurge751
67EuphorDitaxis lanceolatanarrowleaf ditaxis993
68EuphorDitaxis neomexicanaNew Mexico ditaxis 1
69FabaceAcmispon glaber var. brevialatusshort-winged deerweed1 
70FabaceAcmispon maritimus var. brevivexillusshort-bannered coastal lotus 2
71FabaceAcmispon strigosusstrigose lotus 2
72FabaceAstragalus didymocarpus var. dispermusdwarf white milk-vetch 1
73FabaceAstragalus palmeriPalmer's milk-vetch 1
74FabaceLupinus arizonicusArizona lupine 4
75FabacePsorothamnus emoryiEmory's indigo-bush 5
76FabacePsorothamnus schottiiindigo bush 1
77FabacePsorothamnus spinosussmoke tree75 
78FabaceSenegalia greggiicatclaw992
79FouquiFouquieria splendens ssp. splendensocotillo993
80GeraniErodium cicutarium*redstem filaree 1
81GeraniErodium texanumTexas filaree 2
82KramerKrameria bicolorwhite rhatany991
83KramerKrameria erectaPima rhatany251
84LamiacHyptis emoryidesert-lavender993
85LamiacSalvia columbariaechia10 
86LoasacMentzelia affinisyellow blazing star 2
87LoasacMentzelia hirsutissimahairy stickleaf 1
88LoasacMentzelia involucratabracted blazing star 2
89LoasacPetalonyx thurberi ssp. thurberiThurber's sandpaper-plant 1
90MalvacEremalche rotundifoliadesert five-spot 2
91MalvacHibiscus denudatusrock hibiscus202
92MalvacHorsfordia newberryiNewberry's velvet mallow554
93MalvacSphaeralcea ambigua var. ambiguaapricot mallow 1
94MartynProboscidea althaeifoliadesert unicorn-plant 1
95MollugMollugo cerviana*carpet-weed 1
96NyctagAbronia villosa var. villosahairy sand-verbena 1
97NyctagAllionia incarnata var. villosatrailing four o'clock 2
98NyctagBoerhavia triquetra var. intermediafivewing spiderling2 
99NyctagBoerhavia wrightiiWright's spiderling991
100NyctagMirabilis laevis var. retrorsaBigelow's desert four-o'clock 1
101NyctagMirabilis tenuilobaslender-lobed four o'clock17
102OnagraCamissoniopsis pallida ssp. pallidapale suncup 1
103OnagraChylismia cardiophylla ssp. cardiophyllaheartleaf suncup 2
104OnagraChylismia claviformis ssp. peirsoniibrown-eyed primrose999
105OnagraEremothera boothii ssp. condensataBooth's evening primrose15 
106OnagraEremothera chamaenerioideslong-fruit suncup 1
107OnagraEulobus californicusCalifornia suncup993
108PapaveEschscholzia minutiflora ssp. minutiflorasmall-flowered poppy 3
109PapaveEschscholzia parishiiParish's poppy 2
110PhrymaMimulus bigelovii var. bigeloviiBigelow's monkeyflower65
111PlantaAntirrhinum filipesdesert twining snapdragon 1
112PlantaMohavea confertifloraghost flower 1
113PlantaPlantago ovatadesert plantain51
114PolemoGilia capitata ssp. abrotanifoliaglobe gilia 1
115PolygoChorizanthe brevicornu var. brevicornubrittle spineflower 1
116PolygoEriogonum inflatumdesert trumpet152
117PolygoEriogonum thomasiiThomas' buckwheat 1
118RubiacGalium stellatumstar-flowered bedstraw61
119SimmonSimmondsia chinensisjojoba 2
120SolanaDatura wrightiisacred datura 1
121SolanaLycium brevipes var. brevipesdesert-thorn 1
122SolanaLycium fremontiiFremont box-thorn 1
123SolanaNicotiana obtusifoliadesert tobacco 1
124SolanaPhysalis crassifoliathick-leaved ground cherry11
125TamariTamarix ramosissima*saltcedar 1
126UrticaParietaria hespera var. hesperapellitory 1
127ViscacPhoradendron californicumdesert mistletoe174
128ZygophFagonia laevisCalifornia fagonia253
129ZygophLarrea tridentatacreosote bush994
130AgavacAgave deserti var. desertidesert agave18 
131PoaceaAristida purpureapurple three-awn6 
132PoaceaAristida purpurea var. wrightiiWright three-awn 1
133PoaceaBromus madritensis ssp. rubens*red brome2 
134PoaceaFestuca octoflorasix-weeks fescue 2
135PoaceaHilaria rigidabig galleta304
136PoaceaPhragmites australiscommon reed 1
137PoaceaSchismus barbatus*Mediterranean schismus102

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

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Copyright © 2012 by Tom Chester and Kate Harper
Permission is freely granted to reproduce any or all of this page as long as credit is given to us at this source:
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Last update: 18 December 2012