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.
Procedure For Compiling The 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.
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:
- Fieldwork done on 16 December 2012 by Tom Chester and Kate Harper, covering just 0.75 miles of Sweeney Canyon from where it is closest to S2; and
- Vouchers compiled from a search of the Consortium of California Herbaria on 18 December 2012 by Tom Chester.
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:
- using coordinates, for the rectangular box from 32.80 to 32.85° north latitude and -116.22 to -116.16° east longitude; and
- vouchers with Sweeney in their localities.
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:
# Vouchers Collector(s) 85 Larry Hendrickson et al 34 Joe Barth 28 Jon P. Rebman et al 14 Ian 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)
# Family Scientific Name (*) Common Name #Pls #V Ferns 1 Pterid Cheilanthes parryi woolly lipfern 10 2 Gymnosperms 2 Ephedr Ephedra aspera Mormon tea 25 3 Ephedr Ephedra californica desert tea 1 Eudicots 4 Acanth Carlowrightia arizonica Arizona carlowrightia 50 1 5 Acanth Justicia californica chuparosa 99 5 6 Apocyn Asclepias albicans white-stemmed milkweed 3 1 7 Apodan Pilostyles thurberi Thurber's pilostyles 7 8 Astera Adenophyllum porophylloides San Felipe dogweed 5 9 Astera Ambrosia dumosa burroweed 99 2 10 Astera Ambrosia salsola var. salsola cheesebush 99 3 11 Astera Bahiopsis parishii Parish's viguiera 1 12 Astera Bebbia juncea var. aspera sweetbush 30 2 13 Astera Calycoseris wrightii white tackstem 1 14 Astera Chaenactis carphoclinia var. carphoclinia pebble pincushion 99 1 15 Astera Chaenactis stevioides desert pincushion 1 16 Astera Encelia farinosa brittlebush 99 1 17 Astera Ericameria paniculata blackbanded rabbitbrush 1 18 Astera Eriophyllum lanosum white easter-bonnets 1 19 Astera Geraea canescens hairy desert-sunflower 1 20 Astera Logfia depressa dwarf filago 2 21 Astera Malacothrix glabrata desert dandelion 1 22 Astera Palafoxia arida var. arida desert needle 4 4 23 Astera Perityle emoryi Emory's rock-daisy 1 24 Astera Peucephyllum schottii pygmy-cedar 3 25 Astera Pleurocoronis pluriseta arrow-leaf 3 3 26 Astera Rafinesquia neomexicana desert chicory 2 27 Astera Senecio mohavensis Mojave ragwort 3 28 Astera Stephanomeria exigua ssp. exigua slender wreathplant 1 29 Astera Stylocline intertexta tangled nest-straw 1 30 Astera Trichoptilium incisum yellow-head 2 31 Astera Trixis californica var. californica California trixis 2 1 32 Bignon Chilopsis linearis ssp. arcuata desert-willow 2 33 Boragi Amsinckia tessellata var. tessellata bristly fiddleneck 1 34 Boragi Cryptantha angustifolia narrow-leaved cryptantha 5 4 35 Boragi Cryptantha maritima Guadalupe cryptantha 2 2 36 Boragi Cryptantha micrantha var. micrantha red-root cryptantha 2 37 Boragi Emmenanthe penduliflora var. penduliflora whispering bells 1 38 Boragi Eucrypta micrantha desert eucrypta 1 39 Boragi Heliotropium curassavicum var. oculatum seaside heliotrope 1 40 Boragi Pectocarya peninsularis Baja pectocarya 2 41 Boragi Pectocarya recurvata curvenut combseed 1 42 Boragi Phacelia crenulata var. minutiflora little-flowered heliotrope phacelia 1 43 Boragi Phacelia cryptantha limestone phacelia 1 44 Boragi Phacelia distans common phacelia 2 45 Boragi Phacelia pedicellata pedicellate phacelia 1 46 Boragi Tiquilia plicata plicate coldenia 1 47 Brassi Brassica tournefortii *Asian mustard 99 2 48 Brassi Caulanthus lasiophyllus California mustard 1 49 Brassi Dithyrea californica spectacle-pod 1 50 Brassi Draba cuneifolia wedge-leaved draba 1 51 Brassi Lepidium lasiocarpum ssp. lasiocarpum hairy-podded pepper-grass 5 3 52 Brassi Sisymbrium irio *London rocket 2 53 Cactac Cylindropuntia bigelovii teddy-bear cholla 11 1 54 Cactac Cylindropuntia ganderi Gander's cholla 75 2 55 Cactac Ferocactus cylindraceus California barrel cactus 60 56 Cactac Mammillaria dioica California fish-hook cactus 1 2 57 Cactac Mammillaria tetrancistra fish-hook cactus 1 58 Cactac Opuntia basilaris var. basilaris beavertail cactus 6 1 59 Campan Nemacladus rubescens desert nemacladus 1 60 Chenop Atriplex polycarpa cattle saltbush 10 1 61 Convol Cuscuta denticulata desert dodder 1 62 Cucurb Cucurbita palmata coyote melon 2 63 Euphor Acalypha californica California copperleaf 3 64 Euphor Chamaesyce micromera Sonoran spurge 50 65 Euphor Chamaesyce polycarpa small-seeded spurge 40 3 66 Euphor Chamaesyce setiloba starfish (Yuma) spurge 75 1 67 Euphor Ditaxis lanceolata narrowleaf ditaxis 99 3 68 Euphor Ditaxis neomexicana New Mexico ditaxis 1 69 Fabace Acmispon glaber var. brevialatus short-winged deerweed 1 70 Fabace Acmispon maritimus var. brevivexillus short-bannered coastal lotus 2 71 Fabace Acmispon strigosus strigose lotus 2 72 Fabace Astragalus didymocarpus var. dispermus dwarf white milk-vetch 1 73 Fabace Astragalus palmeri Palmer's milk-vetch 1 74 Fabace Lupinus arizonicus Arizona lupine 4 75 Fabace Psorothamnus emoryi Emory's indigo-bush 5 76 Fabace Psorothamnus schottii indigo bush 1 77 Fabace Psorothamnus spinosus smoke tree 75 78 Fabace Senegalia greggii catclaw 99 2 79 Fouqui Fouquieria splendens ssp. splendens ocotillo 99 3 80 Gerani Erodium cicutarium *redstem filaree 1 81 Gerani Erodium texanum Texas filaree 2 82 Kramer Krameria bicolor white rhatany 99 1 83 Kramer Krameria erecta Pima rhatany 25 1 84 Lamiac Hyptis emoryi desert-lavender 99 3 85 Lamiac Salvia columbariae chia 10 86 Loasac Mentzelia affinis yellow blazing star 2 87 Loasac Mentzelia hirsutissima hairy stickleaf 1 88 Loasac Mentzelia involucrata bracted blazing star 2 89 Loasac Petalonyx thurberi ssp. thurberi Thurber's sandpaper-plant 1 90 Malvac Eremalche rotundifolia desert five-spot 2 91 Malvac Hibiscus denudatus rock hibiscus 20 2 92 Malvac Horsfordia newberryi Newberry's velvet mallow 55 4 93 Malvac Sphaeralcea ambigua var. ambigua apricot mallow 1 94 Martyn Proboscidea althaeifolia desert unicorn-plant 1 95 Mollug Mollugo cerviana *carpet-weed 1 96 Nyctag Abronia villosa var. villosa hairy sand-verbena 1 97 Nyctag Allionia incarnata var. villosa trailing four o'clock 2 98 Nyctag Boerhavia triquetra var. intermedia fivewing spiderling 2 99 Nyctag Boerhavia wrightii Wright's spiderling 99 1 100 Nyctag Mirabilis laevis var. retrorsa Bigelow's desert four-o'clock 1 101 Nyctag Mirabilis tenuiloba slender-lobed four o'clock 1 7 102 Onagra Camissoniopsis pallida ssp. pallida pale suncup 1 103 Onagra Chylismia cardiophylla ssp. cardiophylla heartleaf suncup 2 104 Onagra Chylismia claviformis ssp. peirsonii brown-eyed primrose 99 9 105 Onagra Eremothera boothii ssp. condensata Booth's evening primrose 15 106 Onagra Eremothera chamaenerioides long-fruit suncup 1 107 Onagra Eulobus californicus California suncup 99 3 108 Papave Eschscholzia minutiflora ssp. minutiflora small-flowered poppy 3 109 Papave Eschscholzia parishii Parish's poppy 2 110 Phryma Mimulus bigelovii var. bigelovii Bigelow's monkeyflower 6 5 111 Planta Antirrhinum filipes desert twining snapdragon 1 112 Planta Mohavea confertiflora ghost flower 1 113 Planta Plantago ovata desert plantain 5 1 114 Polemo Gilia capitata ssp. abrotanifolia globe gilia 1 115 Polygo Chorizanthe brevicornu var. brevicornu brittle spineflower 1 116 Polygo Eriogonum inflatum desert trumpet 15 2 117 Polygo Eriogonum thomasii Thomas' buckwheat 1 118 Rubiac Galium stellatum star-flowered bedstraw 6 1 119 Simmon Simmondsia chinensis jojoba 2 120 Solana Datura wrightii sacred datura 1 121 Solana Lycium brevipes var. brevipes desert-thorn 1 122 Solana Lycium fremontii Fremont box-thorn 1 123 Solana Nicotiana obtusifolia desert tobacco 1 124 Solana Physalis crassifolia thick-leaved ground cherry 1 1 125 Tamari Tamarix ramosissima *saltcedar 1 126 Urtica Parietaria hespera var. hespera pellitory 1 127 Viscac Phoradendron californicum desert mistletoe 17 4 128 Zygoph Fagonia laevis California fagonia 25 3 129 Zygoph Larrea tridentata creosote bush 99 4 Monocots 130 Agavac Agave deserti var. deserti desert agave 18 131 Poacea Aristida purpurea purple three-awn 6 132 Poacea Aristida purpurea var. wrightii Wright three-awn 1 133 Poacea Bromus madritensis ssp. rubens *red brome 2 134 Poacea Festuca octoflora six-weeks fescue 2 135 Poacea Hilaria rigida big galleta 30 4 136 Poacea Phragmites australis common reed 1 137 Poacea Schismus barbatus *Mediterranean schismus 10 2
Voucher data provided by the participants of the Consortium of California Herbaria (ucjeps.berkeley.edu/consortium/)
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:
Comments and feedback: Tom Chester
Last update: 18 December 2012