Plant Species of the Borrego Desert: 2009-2010 Blooms

punctate rabbitbrush, black-banded rabbitbrush, Chrysothamnus paniculatus
climbing milkweed, Sarcostemma cynanchoides ssp. hartwegii

Both pictures taken on 15 November 2009 in Lower Willows, Coyote Canyon.

Table of Contents

Rainfall This Season

Annual Germination, Growth and Blooms
     General Requirements for Annual Germination
     Peak Bloom: What Does That Mean?
     Summary of Annual Germination, Growth and Blooms in 2008-2009

     Detailed Germination, Growth and Bloom Reports From Each Hike
     Pictures From Each Hike

How Long Will An Annual Bloom Last
     General Factors
     Predictions for This Year

Species in Bloom On Each Trip
     Number of Species and Plants in Bloom On Each Trip
     List of Species in Bloom On Each Trip, With Photographs

Links to Other Webpages on Anza-Borrego Desert State Park Blooms


The Borrego Desert is the northern part of Anza-Borrego Desert State Park below an elevation of 3000 feet, named for the Borrego Valley and the town of Borrego Springs (map and expanded definition).

This page gives information about the 2009-2010 bloom for all species in this area, with emphasis on the annuals that are responsible for the widespread showy blooms that appear in some years on the desert floor. The date of the last update to this page is given at the bottom of this page.

In addition to specific information about current conditions, this page also gives some general information on what is needed to germinate those annuals, and what is needed to sustain the annual bloom.

The information here is by no means a definitive list to what is blooming at all locations in the Borrego Desert; it only records the species I've seen in bloom on my trips that occur roughly every fourth day. Because the locations change, the numbers of species in bloom, and the number of plants in bloom, cannot usually be directly compared from trip to trip. However, the information here will give the reader an idea of what the bloom is doing in the Borrego Desert.

Note that there is often quite a difference in the annual bloom between the moister canyons west of Borrego Springs and the drier areas around the Badlands. Similarly, even within those canyons on the west, there can be large differences between the north-facing and south-facing slopes, and between canyons with permanent water, like Borrego Palm Canyon, and drier canyons. In the drier areas to the east, there can be large differences between the edges of washes and the middle of washes, and between shady canyons and open areas.

The locations for each hike are in the detailed reports below; more information is sometimes given in Botanical Trail Reports in Chronological Order, which usually includes more information about the bloom on each trip.

Rainfall This Season

Rainfall is the most important determinant of blooms. Rainfall is usually highest on the mountain slopes, especially on the west edge of the Borrego Desert, and falls off dramatically with lower elevation to the east. This occurs whenever our rainfall is mostly orographic. However, when rainfall is from convection, the deserts can at times get more rainfall than the coast. (See Precipitation types.)

In addition to desert stations, I've also given the rainfall from my house in Fallbrook, on the coastal side at 680 feet elevation, to show the large difference in rainfall between the wet side of the mountains and the dry side.

Table 1 gives the storm totals, in inches, as of the last day of each storm. The storm totals were taken from the Weather Service Rainfall Storm Summary, except for Fallbrook and the Borrego Badlands. Occasionally other stations are missing in that report; if so, totals are taken from the Rainfall Summary Map.

There is no weather station in the Borrego Badlands; the rainfall estimates are just guesses made from the depth of the wet sand there whenever I visit there.

If a station didn't appear in the summary, or I couldn't find it elsewhere on line, I assumed the rainfall total was zero. Although this assumption is probably usually correct, it is not necessarily always valid since missing data plague all rain reports.

Note that the total rainfall at the bottom of the table is since 1 October, since rain that falls earlier doesn't germinate the desert annuals (see below). This rainfall total may be different from the rainfall reported by the Anza-Borrego Desert State Park Visitor Center using the normal California rainfall year that begins on 1 July.

Table 1. Rainfall Events Since 1 October 2008

DateFallbrookSan FelipeAgua CalienteBorrego Palm CanyonBorrego SpringsBorrego Badlands
13 October 20090.
28 November 20090.420.
Total Since 1 October0.510.

Annual Germination, Growth and Blooms

General Requirements for Annual Germination

The timing of rainfall is extremely important for the annual bloom. Rainfall received in the summer and early fall will not germinate the annuals that bloom in February and March. Rainfall received after January will either not germinate those annuals, or will germinate them too late for them to produce a robust bloom in most years. Thus rain must fall in October, November, and/or December in order to germinate the annuals that produce the showy mass displays.

The amount in a single storm is also important. Native annuals require about an inch of rainfall, received over no longer than a period of something like several days, in order to germinate. Our native annuals have learned the hard way that any less rainfall doesn't guarantee enough moisture in the soil for them to produce seeds.

Unfortunately, non-native annuals can germinate on less rainfall, and can sometimes get a head start over our native annuals if we get a first rainfall much less than an inch.

See Predicting Desert Wildflower Blooms - The science behind the spectacle from the Arizona-Sonora Desert Museum for information relating to Arizona desert blooms.

Peak Bloom: What Does That Mean?

The term Peak Bloom means different things to different people:

Most of the time, I use the latter definition of Peak Bloom, but I also try to mention when the carpets of flowers are present.

If you are looking for a particular species in bloom, the time of Peak Bloom doesn't matter to you; you want to know only when that species is in bloom. Plant species bloom at different times; it is not possible to see every species in bloom even over the time period of a month.

For example, if you want to see the beautiful blooms of beavertail cactus, Opuntia basilaris, you'll need to come just after the showy annual carpets are finished. If you want to see the beautiful flowers of desert-willow, Chilopsis linearis ssp. arcuata, then you'll need to come here in summer, when few species are blooming except for it.

See observed dates of peak bloom in 2008-2009 for various locations.

These annual species produce the showy carpets of flowers:

Other annuals can produce carpets of flowers, but are either more limited in their distribution, such as Bigelow's monkeyflower, Mimulus bigelovii, or purple mat, Nama demissum; or don't produce such showy displays, such as Fremont pincushion, Chaenactis fremontii (since fields of white don't show up well against the whitish background of the desert soil).

Summary of Annual Germination, Growth and Blooms in 2009-2010

Very little or no rain has fallen in most of the Borrego Desert, and hence few winter annuals have germinated. The only place where there may have been germination is in the west-side canyons, or in areas where water has accumulated due to runoff from rock cliffs, etc.

The monsoon was mostly a bust in 2009. There was only a single good storm, in the Elephant Trees Area on 5 September 2009. That storm produced a fabulous display of Pectis papposa, chinch-weed, on 1 October, just 25 days later. As of 23 November 2009, RT Hawke reports that there is a fading bloom still present there, including a few summer annuals. See RT's list of species in bloom below.

For comparison, last year (2008-2009), 0.3 inches of rain fell on 27 November 2008, which resulted in very sparse annual germination, mostly in the canyons on the west side. A widespread rainfall of ~2.0 inches fell on 15-17 December 2008, which produced annual germination throughout the Borrego Desert. This was just in time to produce a good annual display in most places.

See also Summary of Annual Germination, Growth and Blooms in 2008-2009.

Detailed Germination, Growth and Bloom Reports From Each Hike

These reports are just summaries of these conditions from each hike.

See also Detailed Germination, Growth and Bloom Reports From Each Hike in 2008-2009.

10/29/09: Upper Coyote Canyon at and above Middle Willows. This was a car trip between Terwilliger Valley and Middle Willows, with a hike through and around Middle Willows. Only species seen in bloom below 3000 feet elevation are given in Table 4.

The stars were the fall-blooming yellow Asteraceae. It was a real pleasure to see old friends black-banded rabbitbrush, Chrysothamnus paniculatus; and scale-broom, Lepidospartum squamatum in full bloom. They were joined by a number of goldenbush, Isocoma acradenia; and a handful of Mono ragwort, Senecio flaccidus.

The biggest surprise was to find a single bloom of scarlet monkeyflower, Mimulus cardinalis, at Middle Willows. That species was not even on the plant list for the Borrego Desert!

11/15/09: Lower Willows. Thanks to hiking along Coyote Creek, with its abundant flowing water, and the Santa Catarina Spring area, we found a total of 21 species in bloom, most of them the usual suspects like mulefat, Baccharis salicifolia; and goldenbush, Isocoma acradenia, growing in that moist environment.

However, some species were in bloom in drier areas. In Coyote Creek above the Spring, which has no evident water, a number of desert dicoria, Dicoria canescens, were still in bloom. The area near Second Crossing must have gotten a bit of rainfall in the last month or so, since there were over 100 ocotillos in bloom there. Most had only a single or a few flower clusters, and none of them were leafed out. The chuparosa, Justicia californica, also seemed very happy and were blooming along the bypass Jeep Road, aka Boulder Alley.

11/19/09: Culp Valley, Collins Valley, Sheep Canyon. We stopped in Culp Valley on our drive into Borrego Springs to appreciate the wand buckwheat, Eriogonum elongatum, in full bloom, with its wands held high in the air alongside the road.

On our hike to Sheep Canyon, there was a beautiful large field of black-banded rabbitbrush, Chrysothamnus paniculatus, in full bloom at the mouth of Indian Canyon. This would normally have been the highlight of the day bloom-wise, but Sheep Canyon had other ideas.

The lowermost part of Sheep Canyon, up to the Campground, had a number of more coastal species that we had never seen at these low elevations in the Borrego Desert before; I spent much of my time in the canyon with my jaw hanging somewhere near the ground. In particular, it was filled with wand buckwheat in full bloom, as well as California fuchsia, Epilobium canum ssp. latifolium!

11/22/09: Collins Valley, Sheep Canyon. Sheep Canyon continued to surprise above the Campground with more coastal species, including, most improbably, a western sycamore, Platanus racemosa, in full bloom! A number of plants of matchweed, Gutierrezia sarothrae, were in bloom, including one plant with the showiest flowers, with long ligules, that I recall seeing. I had to examine its phyllaries to be sure I was seeing this species.

11/23/09: Elephant Tree Area. RT Hawke reports: The Elephant Tree Loop Trail still had 22 species of plants with flowers. Although most seem to be fading, there are some species (like Fagonia) that are just starting. The leaves of the ocotillo are changing color and starting to drop off. There were fields of Pectis by Split Mt. road, but are now mostly gone. (RT found eight species in addition to the ones listed in the table below which weren't identified to species.)

11/25/09: Box Canyon north of Coyote Creek. Although not a drop of rain has touched Box Canyon itself, three species have a majority of their plants in bloom: matchweed, Gutierrezia sarothrae; Wright's buckwheat, Eriogonum wrightii var. nodosum; and punctate rabbitbrush, Chrysothamnus paniculatus. Coyote Creek continues to have a number of species in bloom along the creek banks.

11/27/09: Montezuma Grade, Clark Valley, Butler Canyon. Mike Crouse reports that he made two surprising finds: a single plant each of bushy cryptantha, Cryptantha racemosa; and heartleaf sun-cup, Camissonia cardiophylla, in bloom in Culp Valley along S22! In Clark Valley and Butler Canyon, there were abundant chuparosa, bebbia and ocotillo in bloom.

Pictures From Each Hike

Most of my pictures were taken for scientific purposes, and not specifically to show anything about the bloom. However, they may be of interest to people showing some aspects of what the bloom was like on a given date. My pictures are not even on standard webpages; Table 2 gives links to a directory and you have to click on the link for each picture to see it. Scientific names are used almost exclusively for the picture names.

The context for most of these pictures is sometimes given in the botanical reports from each hike.

Table 2. Links to Directories With Pictures From Each Trip

October 29
November 15
November 19
November 22
November 25

See also Pictures From Each Hike in 2008-2009.

How Long Will An Annual Bloom Last

General Factors

Past Rainfall, Future Rainfall, and Heat are the main factors determining how long an annual bloom will last on the desert floor at about 1000 feet elevation:

Predictions for This Year

No predictions can be made, since no annuals have germinated yet.

Species in Bloom On Each Trip

Number of Species and Plants in Bloom On Each Trip

Five plots are given below; each plot has this year's bloom data as well as last year's bloom data for comparison:

The plots and the table here must be interpreted cautiously, for at least two reasons:

Figure 1. Number of Species in Bloom on Each Trip

Figure 2. Number of Plants in Bloom on Each Trip

Figure 3. Cumulative Number of Species Seen in Bloom From All Trips

Figure 4. Cumulative Number of Annual Species Seen in Bloom From All Trips

Figure 5. Percent of All Species Seen in Bloom From All Trips That Are Annuals

Table 3 gives the numbers used for the above plots, for the last two months. The individual observations used to obtain these numbers are in the List of Species in Bloom On Each Trip.

Table 3. Number of Species and Total Number of Plants in Bloom on Each Trip

Number of10/2911/1511/1911/2211/2311/2511/27

List of Species in Bloom On Each Trip, With Photographs

Table 4 gives the number of plants observed to be in bloom for each species on each hike, with a maximum value of 99 plants for each species. This maximum value prevents one species from dominating the total plants in bloom, and makes it much easier on me to keep track of the bloom.

Because the hike locations vary, some species will not be present on every hike, so the lack of an entry for a given hike says nothing about whether that species is blooming elsewhere.

The Checklist is sorted first by category, with dicots before monocots, and then by family and scientific name. The Family and Scientific Name are from the Jepson Manual. An asterisk before the Common Name indicates a non-native taxon.

See Plant Family Abbreviations to obtain the full family name from the abbreviations used in the table below.

The Checklist has thumbnail photographs for some of the species. Clicking on the thumbnail photograph gives a larger version equal in size to the ones at the top of this page. I just began adding photographs on 27 November 2009, so it will take a while before all species have photographs.

Some species that have bloomed in the Borrego Desert are not listed here, since I never observed them in bloom. Such species are found only in a few locations, and I either never visited those locations or they bloomed in between my visits to their location.

Of course, species that bloom later in the year, and species that do not have flowers (ferns, etc.) are not present in this list, so it is not the equivalent of a plant checklist for the Borrego Desert.

Table 4. List of Species in Bloom On Each Trip

#FAMScientific NamePixCommon Name10/2911/1511/1911/2211/2311/2511/27
1ACAJusticia californicachuparosa 201550 9999
2AMAAmaranthus fimbriatusfringed amaranth    10  
3ASCAsclepias subulatarush milkweed      2
4ASCSarcostemma cynanchoides ssp. hartwegiiclimbing milkweed 10220   
5ASTAmbrosia dumosaburroweed    3  
6ASTAmbrosia psilostachyawestern ragweed  1050   
7ASTBaccharis salicifoliamule fat1099   3 
8ASTBebbia juncea var. asperasweetbush 51399950
9ASTBrickellia desertorumdesert brickellia  1    
10ASTChrysothamnus paniculatuspunctate rabbitbrush99209999 2099
11ASTConyza canadensishorseweed25     
12ASTDicoria canescensdesert dicoria 30     
13ASTEncelia farinosabrittlebush    3  
14ASTEricameria brachylepisboundary goldenbush  12   
15ASTGutierrezia sarothraematchweed  1020 8 
16ASTIsocoma acradenia var. eremophilasolitary-leaved alkali goldenbush3099   1 
17ASTLepidospartum squamatumscale-broom99      
18ASTPalafoxia arida var. aridadesert needle21011101 
19ASTPectis papposa var. papposachinch-weed    10  
20ASTSenecio flaccidus var. monoensisMono ragwort10      
21ASTSolidago californicagoldenrod   10   
22ASTStephanomeria exigua ssp. exiguaslender wreathplant  2    
23ASTStephanomeria pauciflora var. pauciflorawire-lettuce 51010 210
24ASTViguiera parishiiParish's viguiera   2  1
25BORCryptantha racemosabushy cryptantha      1
26BORHeliotropium curassavicumseaside heliotrope1      
27BORTiquilia plicataplicate coldenia 10     
28CAPIsomeris arboreabladderpod 10   1 
29EUPChamaesyce polycarpasmall-seeded spurge     2 
30EUPCroton californicusCalifornia croton 51    
31EUPDitaxis lanceolatanarrowleaf ditaxis  1    
32FABProsopis glandulosa var. torreyanahoney mesquite     1 
33FABPsorothamnus emoryiEmory's indigo-bush     1 
34FABPsorothamnus schottiiindigo bush    30  
35FOUFouquieria splendens ssp. splendensocotillo 999999 9950
36KRAKrameria grayiwhite rhatany  11 1 
37LAMHyptis emoryidesert-lavender 1122025
38LOAPetalonyx thurberi ssp. thurberiThurber's sandpaper-plant 1     
39MALMalacothamnus fasciculatuschaparral bush mallow1      
40NYCAllionia incarnatatrailing four o'clock    99  
41NYCBoerhavia intermediafivewing spiderling    1  
42NYCMirabilis bigelovii var. retrorsawishbone plant    10  
43ONACamissonia cardiophylla ssp. cardiophyllaheartleaf sun-cup      1
44ONAEpilobium canum ssp. latifoliummountain California-fuchsia  1099   
45ONAEpilobium ciliatum ssp. ciliatumwillowherb1      
46ONAOenothera elata ssp. hirsutissimaHooker's evening-primrose2      
47PLAPlatanus racemosawestern sycamore   1   
48POLEriogonum elongatum var. elongatumlong-stemmed buckwheat 999999 9999
49POLEriogonum inflatumdesert trumpet 1   16
50POLEriogonum wrightii var. nodosumWright's buckwheat   30 21 
51SCRMimulus cardinalisscarlet monkeyflower1      
52SOLDatura wrightiisacred datura 2     
53SOLLycium andersoniiAnderson's desert-thorn 1     
54SOLPhysalis crassifoliathick-leaved ground cherry    1  
55SOLSolanum douglasiiwhite nightshade   2   
56ZYGFagonia laevisCalifornia fagonia    1  
57ZYGLarrea tridentatacreosote bush 5   1 
58LILAgave desertidesert agave  11   
59POAPleuraphis rigidabig galleta    3  

Links to Other Webpages, etc. on Anza-Borrego Desert State Park Blooms

DesertUSA Anza-Borrego Desert State Park Wildflower Reports For 2010

Anza-Borrego Desert Wildflowers: Where and When to Look from the Anza-Borrego Desert Natural History Association

Anza-Borrego Desert State Park Wildflower Hotline: (760)767-4684. "Information on this recording is updated regularly."

Anza-Borrego Foundation and Institute Wildflowers (link didn't work on 9 February 2009)

Theodore Payne Wildflower Hotline (Reports begin in March 2010)

Carol Leigh's California Wildflower Hotsheet

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Copyright © 2008-2010 by Tom Chester.
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Updated 29 November 2009.