Flora of Henderson Canyon
Fig. 1. Henderson Canyon as seen from Borrego Springs Road just south of its intersection with Henderson Canyon Road. The black line is the approximate route of the access road. The light blue line begins at the end of the access road, and shows the typical hiking route up the canyon. The darker blue line shows the lower part of the main channel of the active wash. Click on the picture for a larger version.
Introduction
Location
Botanical Highlights
Trip Reports and Pictures from Henderson Canyon
Field Surveys
Vouchers
Species Notes
Checklist
Introduction
There are three main canyons at the base of the San Ysidro / Hot Springs Mountains immediately west of the town of Borrego Springs. From north to south, they are Henderson Canyon, Borrego Palm Canyon, and Hellhole Canyon. Henderson Canyon is the least well known of these three for three reasons:
- There is no access to Henderson Canyon by paved road, no signs directing visitors to it, and no sign announcing that you are there. One must drive a one mile dirt road to get there, past an open gate and a sign announcing that the road is subject to closure. Update 26 December 2021: the access road is apparently now permanently closed, requiring hikers to hike that one mile dirt road to get to the former parking area.
- There is no trail in Henderson Canyon. One travels through a maze of washes, or goes cross country in rugged terrain. Update 26 December 2021: there is now a very well marked trail going up from the former parking area for 0.5 miles to get into the main drainage.
- Unlike its two more famous sister canyons, Henderson Canyon has no permanent water, no springs, and hence no palm groves or other riparian vegetation.
But those characteristics make Henderson Canyon a delightful canyon to explore. You won't encounter crowds of people, and can get a splendid sense of being alone in the desert while being quite close to Borrego Springs. The open nature of the lower canyon gives good views of Coyote Mountain, the Santa Rosa Mountains, Borrego Springs, the Borrego Badlands, the Salton Sea and the Fish Creek / Vallecito Mountains. The narrow canyons of the upper part are beautiful and can be traveled without the usual thorny vegetation found in wetter areas.
For botanists, this area gives a clear insight into the non-riparian plant species that inhabit alluvial fans, dry washes, and dry canyons. The flora given here is truly representative of such areas, without containing any species that require constant moisture.
But that doesn't mean the species here aren't affected by flowing water! When tropical storms or thunderstorms dump a lot of rain in this canyon, the flood waters can roar through this area. Lindsay and Lindsay (2002) report that flash flooding from Hurricane Doreen in August 1977 caused extensive damage to the De Anza Desert County Club homes in the floodplain of this canyon, with similar flooding in September 1976 and in 1980. Flooding occurred again in 2004 and August 2013. See Flash Flood Species for the species that those floods can bring from higher parts of the canyon to the lower wash.
When you hike this canyon, try to imagine the effect on the landscape and plants from flood waters angrily churning down the existing washes and/or making new washes as they go.
Warning! If you hike this canyon, be sure to either GPS the position of the parking area, or turn around several times on your way up to take careful note of landmarks you can use to return to your car. Once you get only a short distance from your car, it is no longer visible, and hence you cannot get your bearings on it on your return trip. There are a maze of use trails and washlets here, all of which, except one, will take you beyond your car. If you realize you've hiked past your car, simply head north to the access road, and hike that access road directly to your car.
The other tricky spot is on your return trip, leaving the main wash to travel the use trail in the alluvial fan. Again, on the way up, one should either GPS the location where you join the main wash, or carefully note some landmarks you can use to find it.
See Fred Melgert and Carla Hoegen's Henderson Canyon webpage for more information about possible hikes in the canyon, and for a number of beautiful pictures showing the flora of the canyon on their multiple trips there.
Here are pix of the closed gate; a new sign announcing the closure; and a sign forbidding motorized vehicles from traveling into the area.
Location
Fig. 2 shows the location of Henderson Canyon in the Borrego Valley. Henderson Canyon is immediately north of Borrego Palm Canyon, just northwest of Borrego Springs:
Fig. 2. Locator Map for Henderson Canyon in the Borrego Valley Area.
Henderson Canyon should not be confused with Henderson Canyon Road, which begins one mile east of the mouth of Henderson Canyon at Borrego Springs Road and extends seven miles east to its junction with S22 at the Pegleg Smith Monument at the southeast tip of Coyote Mountain. Nearly every wildflower picture on the web labeled Henderson Canyon, and nearly every voucher with the word Henderson Canyon in the locality, was actually taken along Henderson Canyon Road four miles to the east of the mouth of Henderson Canyon in Coyote Creek Wash.
Henderson Canyon is reached by an unnamed dirt road that heads west from the westernmost end of Henderson Canyon Road, at its intersection with Borrego Springs Road (called Santa Rosa Drive on the topo map). The end of that dirt access road is shown in green in Fig. 3. That road is on private property and gated. It is subject to closure by the property owner, but is apparently open nearly all of the time. Visitors are allowed on the road when the road is open. Please respect both the private property and the state park property if you visit here.
Fig. 3 shows the area surveyed for this Flora, which is described in the section Field Surveys.
Fig. 3. Areas surveyed as of January 2013 are shown by the blue and yellow lines in the lower canyon, and the green and red lines in the upper canyon. The blue diamonds are GPS locations of species, usually only taken where a species was first encountered in a given survey, although some species of interest have multiple GPS points in a given survey. The green line at the extreme right is the access road to the parking area.
Botanical Highlights
This canyon contains the only known specimen of Phacelia rotundifolia in the Borrego Desert, and, in fact, all of San Diego County. This species did not appear in any of the Plant Checklists for San Diego County from Beauchamp's 1986 Flora to Rebman and Simpson's 2006 Fourth Edition Checklist. Mike Crouse and Vince Balch found a single plant of this species in their survey on 13 March 2010, shown in Fig. 4. The photographs of this species were accepted as a voucher at SDSU to document the occurrence of this species in the county.
This is the southwestern-most known occurrence of this species.
Subsequent to this discovery, we found a voucher determined as this species from Sentenac Canyon from 1933. Fortunately, Mike Simpson requested a scan of that voucher. That scan shows the voucher was misdetermined, since the flower had exserted stamens, a much more flaring corolla tube than that of P. rotundifolia, with corolla lobes about as long as the tube, instead of being much shorter than the tube, and leaves that were longer than wide, instead of "rotund".
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| Fig. 4. Phacelia rotundifolia from Henderson Canyon on 13 March 2010, by Mike Crouse. Click on pictures to get larger versions. | |
On 12 January 2013, Tom Chester, Mike Crouse, Kate Harper, Vince Balch, and Mary Jo Churchwell attempted to relocate the Phacelia rotundifolia at and near the location remembered by Mike and Vince of the plants, but we didn't see any due to the poor rainfall conditions that year. We surveyed the area again on 6 December 2013, after a good monsoonal season, but found no Phacelia there. 2013-2014 was another poor rainfall season, so no survey was done. Another survey on 25 February 2015 once again found no plants at that location, due to poor germination on the south-facing slope there. No survey was done in 2016 due to the poor rainfall that year as well.
Finally, on 21 March 2017, in a good rainfall year, Fred Melgert and Carla Hoegen spotted six plants very close to the location remembered by Mike and Vince on a southwest-facing base of a ridge! Fred and Carla climbed around the hillside on which the plants were found, but found no additional plants of this species. See Fred and Carla's photographs of P. rotundifolia from that trip.
On 24 March 2017, Tom Chester, Walt Fidler, Keir Morse, Steven Daniel and Jenny Moore did a survey specifically to look for more locations of Phacelia rotundifolia. We surveyed 4.5 miles, including 1.3 miles of the south-facing slope in the vicinity of Mike's location, and 1.1 miles of the north-facing slope on the other side of Henderson Canyon. We found one additional plant in the vicinity of the six plants found by Fred and Carla, and 12 plants at a new location 0.35 miles to the east, on a west-facing part of the base of a ridge. See map showing Tom's survey route (red line) and the P. rotundifolia locations (blue circles with blue diamonds inside). Other members of the search team explored additional areas in the vicinity of the red line as well; we did a lot of climbing in steep areas to examine any rock exposures similar to the known location. The vast majority of similar rock exposures thus do not contain P. rotundifolia.
We intentionally did not voucher any of these plants, or harm the population in any way, since a population of just 19 plants, separated into two populations, is extremely vulnerable to extinction due to population fluctuation. The species might have been more numerous before the severe drought of the last ten years, and it is important that every one of these 19 plants produces as many seeds as possible in order to get its population above the danger zone. If we find a significantly-larger population this year, or if the population rebounds to healthier numbers in subsequent years, one of us will voucher this occurrence.
In the field, without close-up examination, plants of P. rotundifolia look strikingly similar to plants of Perityle emoryi except for their flowers. We were amazed that Mike and Vince were able to spot their original plant, since the thousands of Perityle on these hillsides effectively hide the Phacelia. The only real difference can be seen when both plants are flowering, since Perityle has large flowers, and the Phacelia has tiny flowers. Without close examination, it would be easy to take a Phacelia plant as a Perityle plant that just hadn't started blooming yet. Up close, the leaves of the two species are slightly different in their morphology, but that difference is far too subtle to try to distinguish vegetative specimens in a field survey of non-blooming plants.
Interestingly, the two P. rotundifolia locations are in unusual rock types for our area, a dark metamorphic rock that forms cliffs with only very small crevices for plants to take hold in. See photograph of Mike's location taken on 6 December 2013 and photograph of the new location we found on 24 March 2017. In the latter photograph, Steven Daniel is photographing the P. rotundifolia plants at that location, but the P. rotundifolia plants cannot be seen in that photograph since they are far too small. Most of the white flowers in that photograph on the cliffs are those of Perityle.
We picked our survey route in part from looking at Google Earth, which showed the dark rock in all the cliff areas we searched. However, in the field, most of that dark rock was not in fact similar to the rock on which the P. rotundifolia was found. Most of the dark rock areas seen in the Google Earth image consisted of large boulders that did not form cliffs with crevices, and did not have the same metamorphic rock layers.
We intentionally searched both the south-facing and north-facing slopes of Henderson Canyon, because there are vouchers from both of those habitats. The most common exposure given in vouchers is a south-facing slope, but all orientations are represented in vouchers. One voucher from the north side of the San Bernardino Mountains says it was found on N, E and W facing slopes.
P. rotundifolia appears to grow mostly in unusual rock types, and to greatly prefer limestone habitats. The most common rock type mentioned in vouchers is limestone or dolomite (82 vouchers), followed by basalt / lava (20 vouchers); granite (5 vouchers); and metamorphic rock (1 voucher). The Flora of the Charleston Mountains, Clark County, Nevada says it is found on or below limestone ledges in the Larrea Belt.
We do not know if the dark metamorphic rock on which our two P. rotundifolia locations is found contains limestone or not. Limestone is a fairly rare constituent of the rocks in the Santa Rosa Mountains, but it does occur within the metamorphic rock, and within the West Salton Detachment Fault (=Santa Rosa Cataclastic Zone in Remeika and Lindsay). For example, Anza's Arrow is made of limestone, and there are occasional beds of it in Rattlesnake Canyon. The white streaks in the photograph of the rocks at one of the P. rotundifolia locations might be due to limestone, but we have not verified that this is the case.
Within Henderson Canyon, it would be worthwhile to explore the ridge east of our survey route, since it has habitat very similar to the two known locations. It would also be worthwhile to explore farther up the drainage we partially surveyed on 24 March 2017.
Outside of Henderson Canyon, it would be worth checking locations along the Montezuma Grade of S22 with exposures of both dark metamorphic rock and limestone for other occurrences of P. rotundifolia, as well as the limestone areas in the Santa Rosa Mountain south face.
Monsoonal Species
The fieldwork on 6 December 2013 was done after a very good monsoonal season, which dramatically increased the numbers of plants for some species. For example, we had only found eight plants of Physalis crassifolia in the previous ten surveys, which included surveys done after some monsoonal rain. On 12/6/13 we found hundreds of plants throughout our survey!
Similarly, we had found only 16 plants of Allionia incarnata previously. On 12/6/13 they sometimes tried to trip us as we walked since they were so abundant, with such large mats.
On 12/6/13 we also saw a number of baby Horsfordia newberryi in several places.
One species, Chamaesyce arizonica, is apparently only present here in very good monsoonal years. We had never seen it on previous surveys here, yet it was very abundant on 12/6/13. Although it is said to be a perennial, it appears to behave as an annual in the Borrego Desert.
Some monsoonal species are present here in only small numbers: just five plants of Amaranthus fimbriatus, which mostly lives at higher elevations, and just 13 plants of Pectis papposa.
Although we looked very hard for the following monsoonal species on 12/6/13, we found no trace of them: Chamaesyce micromera, Ditaxis neomexicana, Bouteloua barbata, Abronia villosa, Palafoxia arida and Kallstroemia californica.
Some of these species apparently don't like the habitat here, and the range of others does not quite make it to Henderson Canyon. We found Chamaesyce micromera at the beginning of the dirt access road to Henderson Canyon, one mile below the mouth of Henderson Canyon, but we couldn't find it one mile farther away at the end of that dirt access road at the mouth of Henderson Canyon. Ditaxis neomexicana seems mostly not to live north of S22 in the Borrego Valley west of the Pegleg Monument. Bouteloua barbata doesn't seem to live in the immediate Borrego Springs area, being mostly found at a bit higher elevation to the west and south.
(More highlights to be added, including other species not found here, maps of some species distributions; Kerry Knudsen's find.)
Flash Flood Species
The flash flood of ~25 August 2013 brought down from higher elevations three species that had not previously been seen in any of our surveys of Henderson Canyon:
- two plants of Petalonyx linearis, narrow-leaf sandpaper-plant (Fig. 5), which is extremely rare in ABDSP, and usually occupies extremely hard to reach exposed cliffs;
- three plants of Camissonia cardiophylla, heartleaf suncup, which typically occupies rocky alluvial fans and steep slopes;
- three plants of Eriogonum gracile var. incultum, slender buckwheat, which is usually found at higher elevation than the surveyed areas here.
These species were all found in the lowermost main channel, just above the ABDSP boundary near the De Anza Desert Country Club residences. In addition, five to ten plants of Nicotiana obtusifolia, desert tobacco, were found in this location. This species had been seen previously in Henderson Canyon, but only on the rock cliffs or immediately below them.
Fred Melgert and Carla Hoegen were the first ones to make the amazing find of the two very happy, green and blooming plants of Petalonyx linearis here, on 8 December 2015, and alerted us to their presence here.
The seeds of these four species were most likely deposited by the receding floodwaters, whose water came from the farthest reaches of Henderson Canyon (see below). Many more seeds of these three species were probably in the mud deposited in the De Anza residences, but probably never got a chance to grow there.
When we first saw these species, we thought it would be interesting to see how long these species persist here.
We got the answer when we checked the plants on 4 December 2016. There was no sign of the lower Petalonyx linearis plant, which Fred Melgert and Carla Hoegen had found was detached from its roots on 29 March 2016, either from wind or from gophers. We found the upper plant still attached to its roots, although it appeared to be totally dead.
Four of the five washdown plants of Camissonia cardiophylla (=Chylismia c.) looked to be dead as well, although one of them was alive and blooming.
Hence most of these washdown plants only lived ~two years, germinating in late 2014 / early 2015, blooming in 2015, and dying in 2016.
Here is a bit more explanation of why the receding floodwaters generally come from the farthest reaches of Henderson Canyon:
Every thunderstorm and every flash flood is different, but for simplicity, to understand what generally happens, imagine that intense rain begins to fall uniformly over all of Henderson Canyon. The rain drops coalesce into sheets of water as they cascade down the slopes. The first part of the flood in the lower channel comes from the lower parts of the canyon that are closest to the lower channel, simply because the water from those areas gets there first.As the flood evolves, water from later rainfall in the closer parts of the canyon is joined by water from the first part of the rain storm from more distant parts of the canyon. This creates the maximum flood water, when all parts of the canyon are contributing water.
After the rain stops and the flood ebbs, there is no water in the flood coming from the near parts of the canyon; it is all "late arriving" water coming from the most distant parts of the canyon. This kindler, gentler water flow now begins seeping into the sand in this lower channel as its velocity decreases, and dropping whatever it is carrying there.
The most distant parts of the canyon are the steep uppermost slopes, which are also the locations most likely to contain the parent Petalonyx linearis population. That water undoubtedly carries seeds from that parent population, or perhaps part of a plant or maybe even an entire plant with seeds.
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| Fig. 5. Petalonyx linearis from lowermost Henderson Canyon taken by Tom Chester on 15 December 2015. Left: the plant at the higher location in the lower wash, being photographed by Keir Morse in the top picture. Right: the plant at the lower location in the wash. Note that both plants are at the edges of the wash, and were washed down in a flash flood from a distant parent location. Click on pictures to get larger versions. | |
Trip Reports and Pictures from Henderson Canyon
- Tom Chester's Botanical Trip Report from 2 February 2008.
- Michael Charters' Field Trip Photo Gallery from 14 March 2008.
- Wayne Armstrong's Pictures from Henderson Canyon from 14 March 2008.
- Google Satellite Map showing the terrain of Henderson Canyon.
- View from the northernmost point surveyed looking west up canyon and looking southeast down canyon on 2 February 2008.
Field Surveys
Ten all-day field surveys were done from 2 February 2008 to 12 January 2013, usually by multiple botanists on each survey. A total of 28 person days was spent in the field by 13 botanists. Table 1 gives the survey dates, area surveyed, and botanists participating in the survey. Table 2 details the four different areas surveyed.
Table 1. Field Survey Dates, Locations and Participants
| # | Date | Area Surveyed | Participants |
|---|---|---|---|
| 1 | 02/02/08 | lower canyon | Tom Chester |
| 2 | 03/14/08 | lower canyon | Tom Chester, Wayne Armstrong, Michael Charters, Kate Shapiro |
| 3 | 12/29/08 | south side lower canyon | Tom Chester, James Dillane, Mike Crouse, Kate Shapiro |
| 4 | 01/02/09 | upper canyon, south fork | Tom Chester, Mike Crouse, RT Hawke, Shaun Hawke |
| 5 | 01/07/09 | upper canyon, south fork | Tom Chester, Mike Crouse, Dave Stith |
| 6 | 01/12/09 | upper canyon, north fork | Tom Chester, Mike Crouse, Bill Sullivan |
| 7 | 03/27/09 | south side lower canyon, plus bit of upper canyon north and south forks | Tom Chester |
| 8 | 04/04/09 | upper canyon, south fork | Tom Chester |
| 9 | 03/13/10 | lower canyon | Mike Crouse, Vince Balch |
| 10 | 01/12/13 | lower canyon, bit of upper canyon, north fork | Tom Chester, Mike Crouse, Kate Harper, Vince Balch, Mary Jo Churchwell |
| 11 | 12/06/13 | lower canyon, upper canyon, south fork | Tom Chester, Walt Fidler, James Dillane, Jim Roberts |
| 12 | 02/25/15 | lower canyon | Tom Chester, Mike Crouse, Adrienne Ballwey, Karyn Sauber, Bill Sullivan, Dick O'Donnell, Kristine ? |
| 13 | 12/15/15 | lower canyon | Tom Chester, Kate Harper, Mary Jo Churchwell, Keir Morse |
| 14 | 12/04/16 | lower canyon | Tom Chester, Keir Morse, Mike Crouse, Nancy Accola |
| 15 | 03/24/17 | lower canyon, lowermost side canyon to north | Tom Chester, Walt Fidler, Keir Morse, Steven Daniel, Mary Jo Churchwell (0.5), Jenny Moore |
| 16 | 12/29/19 | south side | Tom Chester, Nancy Accola, Joe Woods |
Table 2. Surveyed Areas of Henderson Canyon
| Area | Description | Color of Route in Fig. 2 |
|---|---|---|
| Lower Canyon | The 2.5 miles from Parking Area to the forks of the upper canyon | blue |
| South Side | A 1.7 mile route along the slopes on the south side of the lower canyon and the first main drainage from the south | yellow |
| Upper Canyon, North Fork | 0.8 mile route up the North Fork of the upper canyon | green |
| Upper Canyon, South Fork | 1.1 mile route up the South Fork of the upper canyon | red |
(results from the surveys to be added)
Vouchers
Jon P. Rebman and Norman Roberts collected 76 vouchers on 22 April 2005, all given as being from a single location.
(More info about the vouchers to be added)
Species Notes
(note on Phacelia cicutaria to be added.)
Checklist for Henderson Canyon
This checklist is compiled from 15 days of fieldwork in Henderson Canyon from February 2008 to March 2017, and from a search of of the Consortium of California Herbaria on 7 January 2013 for species vouchered from this canyon. The fieldwork included prime-time visits in good bloom years, and hence the checklist should be fairly complete.
See:
- Notes on the Scientific Names Used At This Site and
- Information about the links from the Scientific Name and Common Name.
An asterisk before the common name indicates a non-native species.
It is likely that the single plant of Hoffmannseggia microphylla is not native to Henderson Canyon. It was found only on 15 December 2015, just west of the park boundary, very close to the De Anza residential lots.
We've never seen this species in the Borrego Desert (the northern part of Anza Borrego Desert State Park), although it is fairly common in places in the middle and southern half of the Park. This plant was not present in prior surveys of this location. The closest vouchers are 20 miles to the northeast, in the Coachella Valley, and 30 miles to the southeast, at Fish Creek, which is just outside the area we target for our flora. Fred Melgert and Carla Hoegen report that this species is fairly common in the north part of Fish Creek (the Wind Caves area). It seems most likely that this plant either came from a seed from a population planted in the De Anza subdivision, or from a seed carried back to the De Anza area from a resident's trip to Fish Creek or somewhere else where this species occurs naturally.
The column labeled #Pls gives a minimum estimate of the number of plants from the field surveys, up to a maximum of 99 plants, for species seen in the field surveys for which abundances were noted. Species that were vouchered, but have not yet been seen, have a V in this column.
The column labeled #V gives the number of vouchers in Henderson Canyon.
In 2017, RT Hawke found about ten plants of Bromus tectorum. We haven't yet added that to the flora since we would like to check a specimen to make sure it was not an unusual B. berteroanus. While B. tectorum is very scarce at such low elevations on the desert side of the mountains, it certainly is not impossible that it is in Henderson Canyon, since there is a voucher from Borrego Springs itself, and one from the mouth of Indian Canyon in Collins Valley at 1650 feet elevation.
Version for printing, without lines and other text on this page: html (5 pages) or pdf Clickbook booklet (2 double-sided pages). (See printing instructions for an explanation of these options)
Voucher data provided by the participants of the Consortium of California Herbaria (ucjeps.berkeley.edu/consortium/)