Flora of Margarita Peak Area

Physical Setting and Geology
The Flora


Margarita Peak is the highest point in the Santa Margarita Mountains at an elevation of 3189 feet. It is in San Diego County north of Camp Pendleton, south of the San Mateo Canyon Wilderness Area and west of De Luz (see location map).

Although many people think Margarita Peak is part of the Cleveland National Forest, it is part of a privately-owned 1,206 acre parcel south of the Forest. In August 2007, this parcel was purchased by the Trust for Public Land for $3.1 million obtained from the state and federal governments. Nearly $1.6 million came from the California Wildlife Conservation Board. The rest came from Navy funds provided by Congress to purchase lands to form a buffer zone of "no development" next to military bases, in this case Camp Pendleton.

The parcel was turned over to the Fallbrook Land Conservancy to own and manage, with the Navy holding an easement on the land that precludes development. Unfortunately, no funds for stewardship of the parcel came along with the transfer, so the Fallbrook Land Conservancy must raise funds to manage the parcel. If you would like to help, contact them.

It is also easy to confuse Margarita Peak with Margarita Lookout, which is a peak ~0.9 miles to the north / northwest along the main ridge of the Santa Margarita Mountains, within the National Forest.

Margarita Peak is currently closed to the public until the Fallbrook Land Conservancy installs barriers to keep out off-road vehicles and surveys the land for plants and animals. The land will then be opened to the public for hiking, bird watching and other forms of "passive" recreation.

This page gives the flora of the Margarita Peak parcel from the first such survey.

Physical Setting and Geology

This parcel is at the southernmost end of the Santa Ana Mountains, where the mountains are largely terminated by the Santa Margarita River. The coastal plain is to the south. The parcel consists of two north-south ridges on the west and east, with the region in-between heavily dissected by Roblar Creek, a tributary to the Santa Margarita River. (Roblar is oak grove in Spanish.) The two ridges each have a nearly-constant elevation along the ridgeline, with variations of only ~100 feet between peaks, and an overall change in elevation to the south of only ~100 feet. The flatness of these ridges is due to them being remnants of the old fairly-flat landscape before the land was uplifted ~2 million years ago and began to be dissected.

The following map shows the extent, topography and geology of this parcel:

See also Google satellite view of entire parcel and neighboring area.

The parcel is delineated by the blue arrows; the thick light red bands also line the parcel on three sides. The black line along the top is a mostly east-west firebreak and a short trail to Margarita Peak, surveyed on 11/21/07; the green line along the top and right side is the continuation of that firebreak surveyed on 6/13/08. The two yellow lines and one blue line delineate labeled geologic provinces. An elevation profile along the horizontal red arrow near the top is given below.

The parcel is bordered on the north by the Cleveland National Forest, on the west and south by Camp Pendleton, and on the east by private property. The parcel spans 1.95 miles along its northern end, 1.43 miles along its southern end, and averages 1.1 miles in north-south extent except along the extreme westernmost portion.

The highest elevation is 3189 feet at Margarita Peak in the northwest corner. The lowest elevation is ~1480 feet in Roblar Creek on the southernmost edge of the property near its middle, giving a range in elevation of ~1710 feet.

Except for a very small portion north of the fire break shown as the black line at the top of the above map, the entire property burned in 2003. The last previous burn was in (1960?). See Google satellite view showing unburned area.

The large-scale geology of the parcel is delineated by the two yellow contours and one blue contour. The yellow contours are from the 2005 Geologic Map of the Oceanside 30 x 60-minute Quadrangle (see Geologic Map (4.1 MB) and Correlation and description of map units). The dark blue contour is from the 1966 Santa Ana Sheet of the Geologic Map of California.

However, we note that the geology shown on the above map is from aerial photography and/or large-scale surveys. There is considerable disagreement among the three recent geologic maps of this area (see the previous two geologic maps). The interpretation here seems to be the one that matches what we observed on 21 November 2007 and on satellite images.

The description of the units from the 2005 map are:

In much previous literature, similar rocks have been identified as follows:

In the following, we use Bedford, Santiago, quartz-bearing diorite, and granitic simply as easy to understand labels for these rock types.

These geologic units are readily apparent in the topography of this parcel. The following plot is the elevation cross-section at the location of the horizontal red arrow in the previous plot:

There is a distinct change in slope where the rock types change, and the terrain is quite different in each of the units. The quartz-bearing diorite supports the steeper slopes of the higher elevation ridge in the west. Note the change in slope on the east side of this ridge when the rocks change to the mix of granitic and metasedimentary (granitic / Bedford) rocks.

Since the metasedimentary and metavolcanic rocks (Bedford / Santiago) are easily eroded, they cannot support steep slopes except where they are very recently eroded. Thus it is no surprise that the Roblar Creek drainage developed in these rocks, and the valley has a very shallow slope on its sides.

A slope change is again apparent in the east when the rocks change to metasedimentary (Bedford) rocks. The ridge on the east is significantly lower than the ridge on the west, with gentler slopes, due to the weakness of these rocks.

On our survey on 19 November 2007, we found that the soil on the west slope of the Margarita Peak ridgeline is red, whereas the soils are brown on the east slope. This is a bit puzzling since the underlying rocks are the same on both the east and west slope of that ridgeline, as shown in the geologic map and by our casual field observations.

It is expected that the underlying rocks will influence at least some of the species distributions.

See also Pictures of this area and some of these rocks.

The Flora

The property is mapped in Beauchamp (1986) as about 1/3 chamise chaparral, mostly in the Roblar Creek canyon and to its northeast, with the rest mixed chaparral, except for a small amount of southern oak woodland along its northwest edge.

Survey Details

The plant list given below was obtained from two surveys. The first survey was of 1.4 miles on a firebreak along the northwestern edge of the property on 21 November 2007 by the four authors. The survey was done along the black line extending mostly east-west at the top of the above map, and included the sections of the black line slightly north of the property boundary.

The survey sampled many of the environments in the northern part of the property with the notable exclusion of the easternmost ridge. The survey included the Roblar Creek area, the Roblar Creek Valley, the east- and west-facing slopes of the westernmost ridge, and Margarita Peak itself. The survey included all three geologic units in the 2005 geologic map.

Unfortunately, this was possibly the worst time to do a botanical survey in the last 100 years, near the end of a record drought year and near the end of a record drought decade, after a fire had burned most of the property in 2003. Hence this survey is very incomplete for annuals and perennials, and possibly even for shrubs that have not yet returned after the fire.

Many identifications were done from dead plant remnants from as much as two years ago, and few live plants were in bloom. Identifications that we estimated were less than 95% confidence are given with a question mark; ones felt to be 95% confidence are given with a "~"; the others were felt to have almost 100% confidence. However, given the poor condition (for identification) of these plants when surveyed, it is possible that even a few of almost 100% confidence determinations may prove erroneous.

The second survey was done on 13 June 2008, near the end of the blooming season for most species after a decent rainfall year, by Tom Chester and Mike Peters. This survey did not resurvey most of the area of the first survey. Instead, this survey explored 2.4 miles of a cross-section of Roblar Valley and the ridgeline area on the east of this parcel. The route is shown in green on the above map.

The second survey sampled an west-facing slope of the easternmost ridge, the fairly extensive top of that ridge, and a bit of the east-facing slope.

This survey resolved all of the uncertain plant determinations from the first survey, except for four species found only on the first survey. It added a few species also with some uncertainty on their determinations since those species were lacking some elements needed for their confident determination.

Survey Results

The first survey yielded 82 taxa, 68 native and 14 non-native, in the 1.4 miles of surveyed fire break. The second survey yielded 94 taxa, of which 68 taxa were found in the first survey, and 26 were new taxa for the checklist.

The total number of taxa in the checklist below is 108, of which 104 are fairly confidently-identified. Of those 104 taxa, 89 are native and 15 are non-native.

Six of these taxa are in the CNPS Inventory of Rare and Endangered Plants:

CNPS ListLatin NameCommon Name
List 1B.1Arctostaphylos rainbowensisRainbow manzanita
List 1B.3Horkelia truncataRamona horkelia
List 4.2Holocarpha virgata ssp. elongatagraceful tarplant
List 4.3Pickeringia montana var. tomentosachaparral pea
List 4.3Polygala cornuta var. fishiaeFish's milkwort
List 4.3Swertia parryiParry's green-gentian

The location and abundance of these taxa are as follows:

The rarest taxa here, defined as the species found least often in our database of 128 plant trail guides and 85 digitized floras, a total of 213 lists, are in the following table:

# listsTaxon
8Pickeringia montana var. tomentosa
9Horkelia truncata
11Calamagrostis koelerioides
12Arctostaphylos rainbowensis
15Rhamnus tomentella ssp. tomentella
15Styrax officinalis var. redivivus
16Calystegia macrostegia ssp. arida
17Vulpia myuros
18Cheilanthes clevelandii
19Polygala cornuta var. fishiae

For comparison, the taxon on this trail found in the most lists is golden yarrow, Eriophyllum confertiflorum var. confertiflorum, found on 118 lists.

Bush poppy, Dendromecon rigida, is abundant almost throughout the area surveyed, as expected four years after a burn. However, we saw no young plants that are usually found four years after a fire of the other species present here, such as Ceanothus tomentosus, C. crassifolius, S. mellifera, and Eriogonum fasciculatum. Seedlings of these species may have germinated, but succumbed to the severe drought of the last two years.

The area around Margarita Peak escaped the 2003 fire, and has what appears to be a climax community composed almost entirely of just three species: chamise, hoaryleaf ceanothus and Arctostaphylos glandulosa. The area along the eastern ridgeline has very similar portions.

Black sage, Salvia mellifera, and Cleveland sage, S. clevelandii, have an interesting distribution here. Black sage is much less abundant than Cleveland sage, and is found only on west and east ends of our survey, and thus is only on the west-facing slopes. Cleveland sage is found throughout, but drops out in some of the areas that have black sage.

The list of shrubs that we did not find is possibly as interesting as the species we found:

Arctostaphylos glauca
Artemisia californica
Baccharis emoryi 
Baccharis pilularis
Dudleya lanceolata
Malacothamnus sp.
Opuntia vaseyi
Rhamnus crocea 
Rhus integrifolia
Xylococcus bicolor

All of the species on the above list are found in nearby areas, and many of those species are abundant nearby. Each of these species would have easily been observed in our survey if they were present here.

In addition, we saw no Chamaesyce, Cryptantha, or Phacelia species. This was quite surprising, since similar areas at the Santa Rosa Plateau Ecological Reserve would have extensive populations of Cryptantha, and a much larger number of annual species lining the trail.

The only reason that comes to mind for the paucity of annual species along the trail is that this area is in the middle of quite pristine chaparral, which may largely exclude such species.

Species Notes

Rhamnus tomentella, R. californica. We found that the underneath of the leaves on about 90% of the coffeeberry plants here were very hairy and very soft to the touch, which would key to Rhamnus tomentella. However, about 10% of the plants had totally glabrous leaves, and would key to R. californica. We strongly suspect there is only one species here, since we have found similar variation in these coffeeberries wherever we have surveyed, and have simply arbitrarily called them R. tomentella here.

See, for example, notes on the SnJt Devils Slide Trail population.

Calystegia macrostegia. The plants seen on 6/13/08 had the narrow leaves of ssp. tenuifolia, but it is now fairly clear that there is no actual difference between subspecies arida, intermedia, and tenuifolia. We have simply called these plants ssp. arida, just in case the C. macrostegia subspecies other than these three are actually valid.

See Calystegia macrostegia subspecies intermedia and tenuifolia are bogus.

The Plant List

The estimate of abundance for each taxa is given as the number of total plants seen and the number of locations for each species. These numbers are intended to refer to the entire area, so there is no difference between "on-trail" and "off-trail" as applies to our plant trail guides elsewhere.

The main intended use of this abundance estimate is to note which species are uncommon in this parcel. We do not attempt to quantify the relative abundance of common plants. Thus the maximum number of plants given is 99, and the maximum number of locations is 9.

We define a single location to include all areas within a radius of ~0.1 mile. This is much larger than the radius of ~0.01 mile used in our plant trail guide). For example, the Ramona horkelia was found over a stretch of ~0.3 miles, so is reported as being in 3 locations.

Species found only in the Roblar Creek drainage are noted in the column labeled RC. (Roblar is oak grove in Spanish.)

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)

# Latin Name (*)Common Name # Plants # Locations RC

Ferns and Fern Allies

PteridaceaeFern Family
1Cheilanthes clevelandiiscaly lipfern11 
2Pellaea mucronata var. mucronatabird's-foot fern102 
3unk fern11 


AnacardiaceaeSumac Family
4Malosma laurinalaurel sumac105 
5Rhus ovatasugar bush409 
6Rhus trilobatabasketbush11RC
7Toxicodendron diversilobumpoison oak102RC
ApiaceaeCarrot Family
8Foeniculum vulgare*fennel102 
9Lomatium dasycarpum ssp. dasycarpumwoolly-fruited lomatium202 
10Lomatium lucidumshiny lomatium105 
AsteraceaeSunflower Family
11Agoseris grandifloragrand mountain dandelion202 
12Ambrosia psilostachyawestern ragweed101RC
13Artemisia douglasianamugwort101RC
14Baccharis salicifoliamule fat51RC
15Centaurea melitensis*tocalote999 
16Chaenactis artemisiifoliameally white pincushion102 
17Erigeron foliosus var. foliosusleafy daisy109 
18Eriophyllum confertiflorum var. confertiflorumgolden yarrow999 
19Filago gallica*narrowleaf filago999 
20Gnaphalium californicumCalifornia everlasting105 
21Gnaphalium canescens ssp. beneolensfragrant everlasting209 
22Gnaphalium canescens ssp. microcephalumwhite everlasting32 
23Hazardia squarrosa var. grindelioidessaw-toothed goldenbush309 
24Helianthus gracilentusslender sunflower999 
25Heterotheca grandifloratelegraph weed201 
26Holocarpha virgata ssp. elongatagraceful tarplant509 
27Hypochaeris glabra*smooth cat's ear509 
28Lessingia filaginifolia var. filaginifoliaCalifornia-aster51 
29Madia gracilisslender madia101 
30Sonchus oleraceus*sow thistle32 
31Stephanomeria diegensisSan Diego wreathplant309 
32Venegasia carpesioidescanyon sunflower209 
BrassicaceaeMustard Family
34Hirschfeldia incana*shortpod mustard101RC
CaprifoliaceaeHoneysuckle Family
35Lonicera subspicata var. denudatasouthern honeysuckle105 
36Sambucus mexicanablue elderberry22 
CaryophyllaceaePink Family
37Silene laciniata ssp. majorsouthern Indian pink204 
CistaceaeRock-Rose Family
38Helianthemum scopariumrush-rose999 
ConvolvulaceaeMorning Glory Family
39Calystegia macrostegia ssp. aridasouthern California morning-glory109 
CucurbitaceaeGourd Family
40Marah macrocarpus var. macrocarpuswild-cucumber22 
CuscutaceaeDodder Family
41~Cuscuta californica~California dodder102 
EricaceaeHeath Family
42Arctostaphylos glandulosa ssp. zacaensisEastwood manzanita999 
43Arctostaphylos rainbowensisRainbow manzanita209 
EuphorbiaceaeSpurge Family
44Eremocarpus setigerusdove weed101 
FabaceaePea Family
45Lathyrus vestitus var. alefeldiiSan Diego pea11 
46Lotus scoparius var. scopariusdeerweed999 
47Pickeringia montana var. tomentosachaparral pea305 
FagaceaeOak Family
48Quercus acutidensTorrey's scrub oak509 
49Quercus agrifolia var. agrifoliacoast live oak409 
50Quercus wislizeni var. frutescensinterior live oak11 
GentianaceaeGentian Family
51Centaurium venustumcanchalagua309 
52Swertia parryiParry's green-gentian202 
GeraniaceaeGeranium Family
53Erodium brachycarpum*short-fruited filaree11 
GrossulariaceaeGooseberry Family
54Ribes indecorumwhite-flowering currant103 
HydrophyllaceaePhacelia Family
55Eriodictyon crassifolium var. crassifoliumthick-leaved yerba santa205 
LamiaceaeMint Family
56Salvia apianawhite sage11 
57Salvia clevelandiiCleveland sage999 
58Salvia melliferablack sage203 
PapaveraceaePoppy Family
59Dendromecon rigidabush poppy999 
PlantaginaceaePlantain Family
60Plantago lanceolata*English plantain302RC
PolemoniaceaePhlox Family
61Navarretia hamata ssp. hamatahooked skunkweed999 
PolygalaceaeMilkwort Family
62Polygala cornuta var. fishiaeFish's milkwort31RC
PolygonaceaeBuckwheat Family
63Chorizanthe staticoidesTurkish rugging101 
64Eriogonum fasciculatum var. foliolosumCalifornia buckwheat509 
PrimulaceaePrimrose Family
65Anagallis arvensis*scarlet pimpernel309 
RanunculaceaeButtercup Family
66Clematis lasianthavirgin's bower309 
RhamnaceaeBuckthorn Family
67Ceanothus crassifoliushoaryleaf ceanothus309 
68Ceanothus leucodermischaparral whitethorn209 
69Ceanothus tomentosus var. olivaceusRamona-lilac209 
70Rhamnus ilicifoliahollyleaf redberry55 
71Rhamnus tomentella ssp. tomentellahoary coffeeberry109 
RosaceaeRose Family
72Adenostoma fasciculatumchamise999 
73Cercocarpus minutiflorusSan Diego mountain mahogany201RC
74Heteromeles arbutifoliatoyon509 
75Horkelia truncataRamona horkelia506 
76Prunus ilicifolia ssp. ilicifoliahollyleaf cherry55 
RubiaceaeBedstraw Family
77Galium angustifolium ssp. angustifoliumnarrowleaf bedstraw409 
78Galium nuttallii ssp. nuttalliiclimbing bedstraw11 
ScrophulariaceaeSnapdragon Family
79Antirrhinum nuttallianum ssp. nuttallianumpurple snapdragon52 
80Cordylanthus rigidus ssp. setigerusbristly bird's beak999 
81Keckiella cordifoliaheartleaf penstemon103 
82Mimulus aurantiacusbush monkeyflower205 
83Scrophularia californica ssp. floribundaCalifornia bee plant31 
SolanaceaeNightshade Family
84Solanum parishiiParish's purple nightshade55 
StyracaceaeStorax Family
85Styrax officinalis var. redivivusCalifornia snowdrop bush409 
VerbenaceaeVervain Family
86Verbena lasiostachys var. lasiostachyswestern vervain101RC


CyperaceaeSedge Family
87~Carex triquetra~triangular-fruit sedge11 
JuncaceaeRush Family
88Juncus macrophyllus?long-leaved rush?21RC
LiliaceaeLily Family
89Calochortus splendenssplendid mariposa lily102 
90Calochortus weedii var. weediiyellow mariposa lily509 
91Chlorogalum parviflorumsmall-flowered soap plant103 
92Chlorogalum pomeridianum var. pomeridianumsoap plant103 
93Dichelostemma capitatum ssp. capitatumblue dicks101 
94Yucca whippleichaparral yucca509 
95Zigadenus fremontiiwhite star-lily43 
PoaceaeGrass Family
96Achnatherum coronatumgiant needlegrass309 
97Agrostis pallensseashore bentgrass209 
98Avena barbata*slender wild oats309 
99Bromus diandrus*ripgut brome51RC
100Bromus hordeaceus*soft chess101RC
101Bromus madritensis ssp. rubens*red brome999 
102Calamagrostis koelerioidesfire reedgrass209 
103Cortaderia sp.*pampas grass11 
104Elymus glaucus ssp. glaucusblue wildrye31RC
105Gastridium ventricosum*nit grass509 
106Melica imperfectacoast-range melic105 
107Nassella lepidafoothill needlegrass509 
108Vulpia myuros*rattail fescue509 

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Copyright © 2007-2008 by Tom Chester, James Dillane, Wayne Armstrong and Mike Peters
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: 14 June 2008