Plant Guide to Mt. Wilson Toll Road / Horse Trail Loop, Eaton Canyon, San Gabriel Mountains

This is a working list, about which we make no guarantees at all until we officially release it. Use at your own risk!

Introduction and Explanation of Plant Trail Guides

Highlights of This Trail
Plant Communities and Floristics
Fieldwork Dates and Summary of List Changes With Time
The Plant Guide
Comments On Specific Species


Directions to the trailhead:
From I-210 East:
Take the Altadena Drive Exit, and go north on Altadena Drive.
From I-210 West: Take the San Gabriel Boulevard Exit (signed for Eaton Canyon Nature Center), continue past Sierra Madre to Altadena Drive, and turn right (north) on Altadena Drive.

Take Altadena Drive north about 2.5 miles to Crescent Drive and turn right. Turn right at the next block, Pinecrest Drive. The trailhead is at the gate as Pinecrest Drive curves left.

Parking on Pinecrest Drive is limited to 2 hours on the weekdays and not at all on the weekends, thanks to the selfish neighbors there (see 26-1 Eaton Canyon Nature Center to Henninger Flats). So if you'll be there more than 2 hours, simply park one block away.

See also Eaton Canyon and Flora of Lower Eaton Canyon.

Highlights of This Trail

Most people would consider this trail to be in coastal sage scrub. Believe it or not, this trail is in the Mixed Hardwood Forest vegetation classification of Kuchler.

Our list contains 120 taxa, of which 117 have so far been identified, in about 1.49 miles of trail, and 2 of the unidentified species are clearly planted and non-native to Eaton Canyon. Of these 119 taxa, 36 (30%) are non-native. These numbers are all roughly average for trails at this elevation.

The botanical highlights of this trail are:

Plant Communities and Floristics

Number of Unique Taxa On This Trail

The following histogram gives the number of trails in our database that contain each taxon on this trail. We had 73 trails in our database when this histogram was made; 3 of those trails, including this one, are in Eaton Canyon. A number of "1" means the taxon has only been found on this trail among the trails in our database; numbers of "3" or smaller may indicate taxa found only in this area. A number of "1" means the taxon has only been found on this trail among the trails in our database.

We have two additional trails about six miles to the west / northwest.

Number of Trails
Containing A Taxon
Number Of Taxa
On This Trail
% of Taxa
On This Trail
Total Taxa117100%

We found 3 additional species not in the above table, since they have not been identified yet. The unidentified ones are marked with ? or sp in the id? column in the guide, and have no entries in the #all column.

The taxa that are truly unique to this trail or area, out of our 73 trails on 24 January 2004, are:

#allLatin NameCommon NameDistribution in Southern California / Distribution in Trail Guides
1Camissonia confusaSan Bernardino sun-cupSW. It may be uncommon because it is possibly a hybrid between C. hirtella and C. pallida ssp. pallida.
1Encelia actoniActon's enceliasw SnJV and adjacent WTR (Cuyama Valley), w D and adjacent CA-FP. Possibly introduced into this location through seeds carried on automobile tires from near Acton.
1Castilleja foliolosawoolly Indian paintbrushThe Jepson Manual thinks it is only in s ChI, but Munz says coastal sage scrub, chaparral from Baja to northern California. We have it in 15 floras in Southern California.
1Coreopsis bigeloviiBigelow's coreopsisTR, DMoj, n Dson.
2Lepidium virginicum var. robinsoniiRobinson's pepper-grassUncommon; SW.
2Quercus durata var. gabrielensis X Q. engelmanniiEngelmann leather oak hybridSnGb (s slope)
3Delphinium cardinalescarlet larkspurSW. We have it only in 3 front-range SnGb trails.
3Chenopodium botrysJerusalem oakMost of California. We have it only in 2 front-range SnGb trails plus the Manzanita Trail on Mt. Baden-Powell in the SnGb.
3Quercus durata var. gabrielensisSan Gabriel Mtns. leather oakSnGb (s slope)
3Juglans californica var. californicaSouthern California black walnutSCo, s TR, n PR (Santa Ana Mountains). We have it only in 3 front-range SnGb trails.

The following taxa are listed as being found only on this trail or in this area, but are planted specimens:

#allLatin NameCommon NameComment
1Quercus lobataValley oakNative to nw SCo, ChI, WTR, w SnGb, but not to Eaton Canyon.
1Casuarina equisetifoliaAustralian pinePlanted species; non-native.

The following taxa are listed as being found only on this trail or in this area, but are not unique for the reasons given below:

#allLatin NameCommon NameComment
2Eriodictyon crassifoliumthick-leaved yerba santassp id needed
3Hordeum murinumfoxtail barleyplants do not key to subspecies

Both of these are common taxa, which have been identified to subspecies in many other trail lists.

Fieldwork Dates and Summary of List Changes With Time

The following table gives the dates the trail was walked and taxa recorded. After each visit, the table gives the total number of taxa on the list and the breakdown of the taxa without positive identification. See Explanation of Plant Trail Guides to understand the symbols below.

Visit DateVisit ## taxa# "?"# "sp"# "~"# "ssp"

Only the first 0.16 miles was covered on 1/22/04.

We thank Jason Hollinger for the correct identification of Chamaesyce melanadenia in February 2006.

The Plant Guide

Version for printing, without lines and other text on this page (5 pages)

Miles#id?Common NameLatin Name#here#all
0.00   Begin plant guide immediately after passing through gate at Pinecrest Drive; elevation 1320 feet.
0.00r1 mule fatBaccharis salicifolia5 / 228
0.00r2 wild-cucumberMarah macrocarpus var. macrocarpus5 / 234
0.00r3 *smilo grassPiptatherum miliaceum50 / 916
0.00r4 California sagebrushArtemisia californica / 32
0.00r5 *ripgut bromeBromus diandrus / 34
0.00r6 branching phaceliaPhacelia ramosissima var. latifolia20 / 523
0.00r7 *shortpod mustardHirschfeldia incana50 / 938
0.00r8 *Oriental mustardSisymbrium orientale / 7
0.00r9 *white goosefootChenopodium album20 / 211
0.00r10 bur-ragweedAmbrosia acanthicarpa20 / 413
0.00r11 *foxtail barleyHordeum murinum+99 / 93
0.00r12 *redstem filareeErodium cicutarium50 / 532
0.00r13 California buckwheatEriogonum fasciculatum var. foliolosum30 / 538
0.00r14 lanceleaf dudleyaDudleya lanceolata30 / 316
0.00r15 coast live oakQuercus agrifolia var. agrifolia3 / 331
0.00l16 short-leaved cliff-asterMalacothrix saxatilis var. tenuifolia20 / 59
0.01l17 *tree tobaccoNicotiana glauca20 / 515
0.01l18 short-winged deerweedLotus scoparius var. brevialatus+20 / 513
0.01l19 California brickellbushBrickellia californica20 / 523
0.01r20 *slender wild oatsAvena barbata / 19
0.01l21 white everlastingGnaphalium canescens ssp. microcephalum20 / 530
0.01l22 golden yarrowEriophyllum confertiflorum var. confertiflorum20 / 540
0.01l23 bush monkeyflowerMimulus aurantiacus20 / 531
0.01r24 *windmill pinkSilene gallica20 / 521
0.01b25 eucryptaEucrypta chrysanthemifolia var. chrysanthemifolia / 15
0.01r26 long-stemmed buckwheatEriogonum elongatum var. elongatum20 / 517
0.01r27 laurel sumacMalosma laurina3 / 329
0.01l28~blue dicksDichelostemma capitatum ssp. capitatum+ / 28
 l29 Bigelow's spike-mossSelaginella bigelovii20 / 513
0.02l30 narrowleaf bedstrawGalium angustifolium ssp. angustifolium10 / 339
 l31 common bedstrawGalium aparine30 / 520
 l32 prickly cryptanthaCryptantha muricata / 13
 l33 coffee fernPellaea andromedifolia5 / 217
 l34 Robinson's pepper-grassLepidium virginicum var. robinsonii30 / 32
 l35 wild sweetpeaLathyrus vestitus var. vestitus5 / 17
 l36 *common chickweedStellaria media30 / 516
 l37 California polypodyPolypodium californicum20 / 312
 r38 *castor beanRicinus communis20 / 512
 l39 small-flowered melicaMelica imperfecta / 25
 l40 leafy daisyErigeron foliosus var. foliosus / 29
 l41 *sow thistleSonchus oleraceus / 21
 l42 scarlet larkspurDelphinium cardinale5 / 13
 l43 bicolored everlastingGnaphalium bicolor10 / 320
 l44 southern Indian pinkSilene laciniata ssp. major10 / 211
 l  liverworts
 l45sp*rose cloverTrifolium hirtum / 5
 l46 California everlastingGnaphalium californicum2 / 124
 r47 *petty spurgeEuphorbia peplus / 6
 l48~globe giliaGilia capitata ssp. abrotanifolia10 / 14
 l49 California chicoryRafinesquia californica / 14
0.07   Road turns right at drainage. Plants downhill are mostly weedy non-natives; plants uphill are mostly native.
 r50 giant wild ryeLeymus condensatus5 / 122
 l51 California suncupCamissonia californica / 13
 l52 wild canterbury bellsPhacelia minor / 12
 l53 chiaSalvia columbariae30 / 517
 l54 white sageSalvia apiana20 / 527
 l55 *goldentopLamarckia aurea / 11
 l56 California dodderCuscuta californica var. californica / 12
 l  San Gabriel thrust fault exposed; look for bedrock on top of alluvium!
 l57 *Spanish broomSpartium junceum5 / 27
 r58 *narrowleaf filagoFilago gallica / 29
 l59 *red bromeBromus madritensis ssp. rubens / 35
 l60 *hairy rattail fescueVulpia myuros var. hirsuta / 9
 l61 *tocaloteCentaurea melitensis5 / 132
 l62 *common groundselSenecio vulgaris3 / 111
0.13l  Jct. Altadena Crest Trail
 r63 Coulter's lupineLupinus sparsiflorus30 / 57
 l64 *Jerusalem oakChenopodium botrys5 / 13
 l65 chaparral yuccaYucca whipplei3 / 320
 l66 San Bernardino sun-cupCamissonia confusa / 1
 r67 *giant reedArundo donax5 / 27
    (bird's-foot fern, Pellaea mucronata var. mucronata)
 l67 Vasey's prickly pearOpuntia Xvaseyi1 / 115
 l68~popcorn flowerCryptantha intermedia / 18
0.15   Beginning of bridge over Eaton Wash; elevation 1240 feet.
 b69 white alderAlnus rhombifolia3 / 19
0.16   End bridge
 l  Check for Nevin's brickellia, Brickellia nevinii.
0.16r  Jct. Eaton Canyon Park Main Road; continue straight on Toll Road.
 l70 California fuchsiaEpilobium canum ssp. canum / 11
 r71sp*Cypress sp.Cupressus sp.+ / 1 
 l72sspthick-leaved yerba santaEriodictyon crassifolium / 2
 r73 dwarf lupineLupinus bicolor / 17
 l74 California poppyEschscholzia californica / 20
 l75 creek senecioSenecio flaccidus var. douglasii / 9
 l76 *bermuda grassCynodon dactylon / 15
 l77 collar lupineLupinus truncatus / 16
 r78 *smooth cat's earHypochaeris glabra / 21
 r79 birch-leaf mountain-mahoganyCercocarpus betuloides var. betuloides / 14
 r80 annual sunflowerHelianthus annuus / 8
 r81sp*planted 3 needle (Jeffrey?) pinePinus sp.+ /  
 r82 *Valley oakQuercus lobata+ / 11
 r  Large drain on ridgeline.
 r83 *black locustRobinia pseudoacacia+ / 16
0.43   Cross drainage
 l  Best field of Coulter's lupine, Lupinus sparsiflorus.
 r  Road drain.
 l84 pygmy-weedCrassula connata / 11
 r  Turnout.
 r85 Acton's enceliaEncelia actoni / 1
 r  Road drain.
 r  Turnout.
 r86 *Australian pineCasuarina equisetifolia+ / 1
 r  Sign with Bicycle Rules
 l87 black sageSalvia mellifera / 29
 r  Road drain.
 r88 *California burcloverMedicago polymorpha / 26
 l  (Giant needlegrass, Achnatherum coronatum)
 l89 white nightshadeSolanum douglasii / 12
    Cross weird drainage.
 l90 red-gland spurgeChamaesyce melanadenia / 8
 r91 stinging lupineLupinus hirsutissimus / 11
 r  Small drain.
 l92 *fountain grassPennisetum setaceum / 8
0.62   Cross drainage with interesting alcove / dry waterfall on left.
 l93 hollyleaf redberryRhamnus ilicifolia / 31
0.85   Cross large drainage with a flat-topped low retaining wall, good for sitting on.
 l94 bittercressCardamine oligosperma / 5
 l95 threadstemPterostegia drymarioides / 14
 l96 narrow-leaved miner's lettuceClaytonia parviflora ssp. parviflora / 8
 l97 miner's lettuceClaytonia perfoliata ssp. perfoliata / 12
 l98 hollyleaf cherryPrunus ilicifolia ssp. ilicifolia / 9
 l99 heartleaf penstemonKeckiella cordifolia / 19
 r100 poison oakToxicodendron diversilobum / 29
 r101 toyonHeteromeles arbutifolia / 35
 l102 goldback fernPentagramma triangularis ssp. triangularis / 12
 l103 California lace fernAspidotis californica / 4
 l104 woolly Indian paintbrushCastilleja foliolosa / 1
0.98r  Jct. Horse Trail down to lower Eaton Canyon; take it; elevation 1635 feet.
 l105 south coast morning-gloryCalystegia macrostegia ssp. intermedia / 12
 l106 sugar bushRhus ovata / 19
 r107?the unknown ~agave mystery plant from sunset ridge
 l  Firecracker Plantation, where the 1993 fire was started by a transient.
 l  (Unk. pine tree, not P. halapensis)
 r108 *oliveOlea europaea / 8
 r109 saw-toothed goldenbushHazardia squarrosa var. grindelioides / 26
 l110 Bigelow's coreopsisCoreopsis bigelovii / 1
 r111 San Gabriel Mtns. leather oakQuercus durata var. gabrielensis / 3
 b112 chamiseAdenostoma fasciculatum / 27
 r113 *Russian thistleSalsola tragus / 22
 r114 bristly goldenasterHeterotheca sessiliflora ssp. echioides / 5
 r  (blue elderberry, Sambucus mexicana)
 l115?Helianthus gracilentus?
 l116 Engelmann leather oak hybridQuercus durata var. gabrielensis X Q. engelmannii / 2
 r117 blue elderberrySambucus mexicana / 34
 r  (Check for possible Quercus durata X Q. berberidifolia.)
 l118 Southern California black walnutJuglans californica var. californica / 3
 l119 *blue gumEucalyptus globulus / 4
 r120 California coffeeberryRhamnus californica ssp. californica / 12
1.49   End guide at jct. with Main Eaton Canyon Road; elevation 1080 feet.

Comments On Specific Species

Hordeum murinum. These are perfect ssp. leporinum in Munz, with 4.7 spikelets per cm of rachis, male lateral spikelets, and an inflorescence that is partially sheathed. However, they key to ssp. glaucum in JM, with the central floret slightly < lateral florets and the anthers of lateral florets ~2x anthers of central floret! The central lemma awn is slightly longer than the lateral lemma awns, not shorter, per the JM description.

Hence we have chosen to not give a subspecies here, and will accumulate further data from other locations to see how common this situation is.

Lotus scoparius var. brevialatus. The subspecies was determined from plants later on the trail; thus it is possible that this specimen is var. scoparius, since both varieties are found in the vicinity.

Dichelostemma capitatum ssp. capitatum. Only leaves were seen at this location, hence the ~ in the id? column. This taxon was found later on the trail.

Cupressus sp., Pinus sp., Quercus lobata, Robinia pseudoacacia, and Casuarina equisetifolia. The Sierra Club hikers who use this trail, in a well-intentioned by uninformed action, planted these species along the south side of the trail to eventually provide shade for hikers and bikers along this very unshaded route.

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Copyright © 2003-2006 by Jane Strong and Tom Chester.
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: Jane Strong | Tom Chester
Updated 25 February 2006.