Flora of Margarita Peak Area
Physical Setting and Geology
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:
- Mzu. Metasedimentary and metavolcanic rocks undivided (Mesozoic) - Wide variety of low- to high-metamorphic grade metavolcanic and metasedimentary rocks that are mostly volcaniclastic breccia and metaandesitic flows, tuffs and tuff-breccia.
- Khg. Heterogeneous granitic rocks (Cretaceous) - A wide variety of heterogeneous granitic rocks occur in Oceanside quadrangle. Some heterogeneous assemblages include large proportions of metamorphic rocks.
- Kgdfg. Quartz-bearing diorite undivided (mid-Cretaceous) - Mostly massive, medium-grained, dark-gray biotite-hornblende quartz-bearing diorite.
In much previous literature, similar rocks have been identified as follows:
- The metasedimentary rocks have been called the Bedford Canyon Formation, the former sea floor sediments from ~100 - ~200 million years ago that were metamorphosed by plutonic activity ~100 million years ago. This formation is easily weathered and generally is not exposed on the surface except where there has been recent erosion.
- The metavolcanic rocks have been called the Santiago Peak Metavolcanics, and are typically found in a narrow band along the west edge of southern Riverside and San Diego Counties. These were basaltic lavas erupted from volcanoes of ~100 million years ago, deposited on portions of the Bedford Canyon Formation. This formation is also easily weathered and generally is not exposed on the surface.
- The quartz-bearing diorite, and the granitic rocks, have been called the Woodson Mountain Granodiorite, the Bonsall Tonalite, and the San Marcos gabbro. The rocks formed in the cooled magma chambers of ~100 million years ago. Some of these rocks are fairly resistant to erosion, and often are exposed at the surface.
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 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.
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.
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 List Latin Name Common Name List 1B.1 Arctostaphylos rainbowensis Rainbow manzanita List 1B.3 Horkelia truncata Ramona horkelia List 4.2 Holocarpha virgata ssp. elongata graceful tarplant List 4.3 Pickeringia montana var. tomentosa chaparral pea List 4.3 Polygala cornuta var. fishiae Fish's milkwort List 4.3 Swertia parryi Parry's green-gentian
The location and abundance of these taxa are as follows:
- Arctostaphylos rainbowensis. We found about 20 mature specimens that showed no evidence of hybridization with the much more abundant A. glandulosa. These specimens all had globose burls, glabrous stems and twigs, and scale-like inflorescence bracts ~2 mm in length throughout. One specimen had fruit, which was purplish.
We examined numerous specimens of A. glandulosa ssp. zacaensis; none showed any evidence of hybridization with A. rainbowensis. All examined specimens had hairy or glandular-hairy twigs, and lower inflorescence bracts that were leaf-like, 5-10 mm in length. All fruit were a light red color, without any purplish color. Burls tended to be flat-topped, but many specimens were young and their burls were indistinguishable from a globose burl.
Thus these two species appear to not interbreed here.
- Horkelia truncata. This property has one of the largest collections that we have seen. This species is numerous on the disturbed area below the fireroad, from Roblar Creek west to the beginning of the eastern slope at the base of Margarita Peak. This species was only found in the Bedford / Santiago geologic unit, but it may just prefer the flattish slopes found in that unit.
- Holocarpha virgata ssp. elongata. We found ~50 plants of this annual, on the slopes above Roblar Creek and on the western slopes below Margarita Peak.
- Pickeringia montana var. tomentosa. The eastern ridgeline has at least 30 plants of this species, concentrated to one location.
- Polygala cornuta var. fishiae. We found three plants in the short section of Roblar Creek we surveyed, and expect it lines at least portions of the Creek.
- Swertia parryi. This species is found in the Roblar Creek drainage near the bottom, a minimum of 20 plants.
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:
# lists Taxon 8 Pickeringia montana var. tomentosa 9 Horkelia truncata 11 Calamagrostis koelerioides 12 Arctostaphylos rainbowensis 15 Rhamnus tomentella ssp. tomentella 15 Styrax officinalis var. redivivus 16 Calystegia macrostegia ssp. arida 17 Vulpia myuros 18 Cheilanthes clevelandii 19 Polygala 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.
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
Pteridaceae Fern Family 1 Cheilanthes clevelandii scaly lipfern 1 1 2 Pellaea mucronata var. mucronata bird's-foot fern 10 2 3 unk fern 1 1
Anacardiaceae Sumac Family 4 Malosma laurina laurel sumac 10 5 5 Rhus ovata sugar bush 40 9 6 Rhus trilobata basketbush 1 1 RC 7 Toxicodendron diversilobum poison oak 10 2 RC Apiaceae Carrot Family 8 Foeniculum vulgare *fennel 10 2 9 Lomatium dasycarpum ssp. dasycarpum woolly-fruited lomatium 20 2 10 Lomatium lucidum shiny lomatium 10 5 Asteraceae Sunflower Family 11 Agoseris grandiflora grand mountain dandelion 20 2 12 Ambrosia psilostachya western ragweed 10 1 RC 13 Artemisia douglasiana mugwort 10 1 RC 14 Baccharis salicifolia mule fat 5 1 RC 15 Centaurea melitensis *tocalote 99 9 16 Chaenactis artemisiifolia meally white pincushion 10 2 17 Erigeron foliosus var. foliosus leafy daisy 10 9 18 Eriophyllum confertiflorum var. confertiflorum golden yarrow 99 9 19 Filago gallica *narrowleaf filago 99 9 20 Gnaphalium californicum California everlasting 10 5 21 Gnaphalium canescens ssp. beneolens fragrant everlasting 20 9 22 Gnaphalium canescens ssp. microcephalum white everlasting 3 2 23 Hazardia squarrosa var. grindelioides saw-toothed goldenbush 30 9 24 Helianthus gracilentus slender sunflower 99 9 25 Heterotheca grandiflora telegraph weed 20 1 26 Holocarpha virgata ssp. elongata graceful tarplant 50 9 27 Hypochaeris glabra *smooth cat's ear 50 9 28 Lessingia filaginifolia var. filaginifolia California-aster 5 1 29 Madia gracilis slender madia 10 1 30 Sonchus oleraceus *sow thistle 3 2 31 Stephanomeria diegensis San Diego wreathplant 30 9 32 Venegasia carpesioides canyon sunflower 20 9 33 *thistle 1 1 Brassicaceae Mustard Family 34 Hirschfeldia incana *shortpod mustard 10 1 RC Caprifoliaceae Honeysuckle Family 35 Lonicera subspicata var. denudata southern honeysuckle 10 5 36 Sambucus mexicana blue elderberry 2 2 Caryophyllaceae Pink Family 37 Silene laciniata ssp. major southern Indian pink 20 4 Cistaceae Rock-Rose Family 38 Helianthemum scoparium rush-rose 99 9 Convolvulaceae Morning Glory Family 39 Calystegia macrostegia ssp. arida southern California morning-glory 10 9 Cucurbitaceae Gourd Family 40 Marah macrocarpus var. macrocarpus wild-cucumber 2 2 Cuscutaceae Dodder Family 41 ~Cuscuta californica ~California dodder 10 2 Ericaceae Heath Family 42 Arctostaphylos glandulosa ssp. zacaensis Eastwood manzanita 99 9 43 Arctostaphylos rainbowensis Rainbow manzanita 20 9 Euphorbiaceae Spurge Family 44 Eremocarpus setigerus dove weed 10 1 Fabaceae Pea Family 45 Lathyrus vestitus var. alefeldii San Diego pea 1 1 46 Lotus scoparius var. scoparius deerweed 99 9 47 Pickeringia montana var. tomentosa chaparral pea 30 5 Fagaceae Oak Family 48 Quercus acutidens Torrey's scrub oak 50 9 49 Quercus agrifolia var. agrifolia coast live oak 40 9 50 Quercus wislizeni var. frutescens interior live oak 1 1 Gentianaceae Gentian Family 51 Centaurium venustum canchalagua 30 9 52 Swertia parryi Parry's green-gentian 20 2 Geraniaceae Geranium Family 53 Erodium brachycarpum *short-fruited filaree 1 1 Grossulariaceae Gooseberry Family 54 Ribes indecorum white-flowering currant 10 3 Hydrophyllaceae Phacelia Family 55 Eriodictyon crassifolium var. crassifolium thick-leaved yerba santa 20 5 Lamiaceae Mint Family 56 Salvia apiana white sage 1 1 57 Salvia clevelandii Cleveland sage 99 9 58 Salvia mellifera black sage 20 3 Papaveraceae Poppy Family 59 Dendromecon rigida bush poppy 99 9 Plantaginaceae Plantain Family 60 Plantago lanceolata *English plantain 30 2 RC Polemoniaceae Phlox Family 61 Navarretia hamata ssp. hamata hooked skunkweed 99 9 Polygalaceae Milkwort Family 62 Polygala cornuta var. fishiae Fish's milkwort 3 1 RC Polygonaceae Buckwheat Family 63 Chorizanthe staticoides Turkish rugging 10 1 64 Eriogonum fasciculatum var. foliolosum California buckwheat 50 9 Primulaceae Primrose Family 65 Anagallis arvensis *scarlet pimpernel 30 9 Ranunculaceae Buttercup Family 66 Clematis lasiantha virgin's bower 30 9 Rhamnaceae Buckthorn Family 67 Ceanothus crassifolius hoaryleaf ceanothus 30 9 68 Ceanothus leucodermis chaparral whitethorn 20 9 69 Ceanothus tomentosus var. olivaceus Ramona-lilac 20 9 70 Rhamnus ilicifolia hollyleaf redberry 5 5 71 Rhamnus tomentella ssp. tomentella hoary coffeeberry 10 9 Rosaceae Rose Family 72 Adenostoma fasciculatum chamise 99 9 73 Cercocarpus minutiflorus San Diego mountain mahogany 20 1 RC 74 Heteromeles arbutifolia toyon 50 9 75 Horkelia truncata Ramona horkelia 50 6 76 Prunus ilicifolia ssp. ilicifolia hollyleaf cherry 5 5 Rubiaceae Bedstraw Family 77 Galium angustifolium ssp. angustifolium narrowleaf bedstraw 40 9 78 Galium nuttallii ssp. nuttallii climbing bedstraw 1 1 Scrophulariaceae Snapdragon Family 79 Antirrhinum nuttallianum ssp. nuttallianum purple snapdragon 5 2 80 Cordylanthus rigidus ssp. setigerus bristly bird's beak 99 9 81 Keckiella cordifolia heartleaf penstemon 10 3 82 Mimulus aurantiacus bush monkeyflower 20 5 83 Scrophularia californica ssp. floribunda California bee plant 3 1 Solanaceae Nightshade Family 84 Solanum parishii Parish's purple nightshade 5 5 Styracaceae Storax Family 85 Styrax officinalis var. redivivus California snowdrop bush 40 9 Verbenaceae Vervain Family 86 Verbena lasiostachys var. lasiostachys western vervain 10 1 RC
Cyperaceae Sedge Family 87 ~Carex triquetra ~triangular-fruit sedge 1 1 Juncaceae Rush Family 88 Juncus macrophyllus? long-leaved rush? 2 1 RC Liliaceae Lily Family 89 Calochortus splendens splendid mariposa lily 10 2 90 Calochortus weedii var. weedii yellow mariposa lily 50 9 91 Chlorogalum parviflorum small-flowered soap plant 10 3 92 Chlorogalum pomeridianum var. pomeridianum soap plant 10 3 93 Dichelostemma capitatum ssp. capitatum blue dicks 10 1 94 Yucca whipplei chaparral yucca 50 9 95 Zigadenus fremontii white star-lily 4 3 Poaceae Grass Family 96 Achnatherum coronatum giant needlegrass 30 9 97 Agrostis pallens seashore bentgrass 20 9 98 Avena barbata *slender wild oats 30 9 99 Bromus diandrus *ripgut brome 5 1 RC 100 Bromus hordeaceus *soft chess 10 1 RC 101 Bromus madritensis ssp. rubens *red brome 99 9 102 Calamagrostis koelerioides fire reedgrass 20 9 103 Cortaderia sp. *pampas grass 1 1 104 Elymus glaucus ssp. glaucus blue wildrye 3 1 RC 105 Gastridium ventricosum *nit grass 50 9 106 Melica imperfecta coast-range melic 10 5 107 Nassella lepida foothill needlegrass 50 9 108 Vulpia myuros *rattail fescue 50 9