The Flora of the PCT
San Ysidro Mountains B3, Highway 79 (underpass second crossing) to Chihuahua Valley Road / Lost Valley Road

Fig. 1. Left: fringe-pod, Thysanocarpus curvipes. Right: showy bajada lupine, Lupinus concinnus ssp. optatus. Pictures taken 16 March 2014 by Tom Chester. Click on the pictures for larger versions.
See also a number of pictures from the lower trail from 23 November 2015, and from south of Lost Valley Road from 15 November 2015, both galleries by Fred Melgert

SegmentSegment StartSegment EndSegment LengthElevation (feet)
B3Highway 79 (underpass second crossing), 2940 feetChihuahua Valley Road / Lost Valley Road, 5060 feet15.0 miles294052402300
   B3aHighway 79 (underpass second crossing), 2940 feetIndian Flats Road 9S05 (= Lost Creek Road = Lost Hills Road), 4190 feet7.0 miles*294041901250
   B3bIndian Flats Road 9S05 (= Lost Creek Road = Lost Hills Road), 4190 feetChihuahua Valley Road / Lost Valley Road, 5060 feet8.0 miles*41905060870
This section covers roughly mile 112 to mile 127 from the Mexican Border (see notes on accuracy of mileages).
Topo! gives 14.7 miles for this segment. The PCT Data Book gives 15.9 miles. We've adopted 15.5 miles.
The one-way hike from south to north has a total elevation gain of 3170 feet, and a total elevation loss of 1050 feet see the profile below.
The one-way hike from north to south has a total elevation gain of 1050 feet, and a total elevation loss of 3170 feet.
A round-trip hike of this section is 30.0 miles, with an elevation gain and loss of 4220 feet.
*An additional hike of 0.5 miles, with 220 feet of elevation gain, is required to access the breakpoint between B3a and B3b.

Survey Dates
The Trail Plant Checklist


See The Flora of the Pacific Crest Trail: Overview for an Introduction to these plant checklists, and B. The San Ysidro and San Jacinto Mountains for an Introduction to the San Ysidro and San Jacinto Mountains section.

At the start of this section, there is convenient roadside parking on Highway 79 0.1 miles west of the Agua Caliente Bridge, near milepost 36.6. This section of the PCT begins where it crosses under that bridge. A gated access road leads to a junction with the PCT in 0.12 miles, which is 0.05 miles into this section.

This section starts with 1.3 miles of a beautiful open riparian area, with cottonwoods, coast live oaks and pine goldenbush that are just as pretty in fall as in spring. The trail then climbs out of Agua Caliente Creek, giving good views of the Lake Henshaw Basin and Palomar Mountain. At mile 3.2, the trail rejoins the creek in an even more-beautiful narrow riparian area enclosed by steep canyon walls made of Julian Schist, with several nice campsites. At mile 4.5, the trail leaves the creek for good and climbs around the western base of the San Ysidro Mountains to a junction with a 0.5 mile gated road off of the road to the Indian Flats Campground, Lost Valley Road. That junction is the end of section B3a. The lower end of that gated road is reached by driving 4.4 miles up the Lost Valley road that connects to SR79.

Section B3b then cuts through the northwest side of the San Ysidro Mountains, enters Anza Borrego Desert State Park at mile 12.5, then ends at a saddle which is the drainage divide between the coastal drainage it had been in, and the interior drainage of Coyote Creek headed to Borrego Springs. The Chihuahua Valley Road / Lost Valley Road crosses the PCT at that saddle.

There is quite a bit of confusion about the names of the roads are in this area. First, the road to Indian Flats Campground, from SR79 just west of Warner Springs, is variously called Lost Creek Road, Lost Hills Road, and 9S05 in different references, and is signed Indian Flats Road at SR79. The name of this road changes to "Puerta La Cruz Road" at Pine Mountain and then connects to Chihuahua Valley Road four miles west of SR79.

The saddle where this segment ends is ~11.2 miles east of SR79 along Chihuahua Valley Road / Lost Valley Road. The name of the road at that point is different in different sources. The PCT books call it "Chihuahua Valley Road", but Google Maps calls it "Lost Valley Road". In any case, this Lost Valley Road, accessed from Chihuahua Valley Road, is not the same as the Lost Valley Road near Warner Springs. See PCT Lost Valley for detailed instructions as to how to access this saddle.


Fig. 2. Left: Trail Map for the PCT Section B3, Highway 79 (underpass second crossing) to Chihuahua Valley Road, from USDA Forest Service Interactive Map. Right: Elevation profile from B3, Highway 79 (underpass second crossing) to Chihuahua Valley Road, from south to north. Click on the pictures for larger versions.

Survey Dates

DateSurveyors# Species known on trail
cumulative from all surveys to date
12 May 2007 to 26 August 2012Charles Wolfinger (19 vouchering trips to parts of the upper trail area; not a survey of the trail per se)164*
4, 6 March 2014RT and Shaun Hawke161*
16 March 2014RT and Shaun Hawke, Tom Chester, Keir Morse, Jim Roberts, Angelique Herman, Anne Kelly
13 April 2014RT and Shaun Hawke
23 November 2015Tom Chester, Kate Harper, Jim Roberts, Carla Hoegen, Fred Melgert, Mike Crouse333
* The first two entries give the number of taxa known from those individual surveys / trips.

Of the 333 taxa known from all surveys of the trail as of 23 November 2015, 239 were confidently identified from our surveys; an additional 15 taxa were found, but have not yet been confidently identified; and an additional 79 taxa have been vouchered from the trail itself or nearby.

The vast majority of the vouchers in section B3 are from Charles Wolfinger, who may have the record for the number of vouchers on any section of the PCT, let alone on such a remote section! Charles has 188 vouchers from this section; and Nancy Nenow and collaborators have 37 vouchers from this section, from a total of 177 taxa (some species have multiple vouchers). Many of the 19 trips made by Charles to the hard-to-reach upper section of this segment were summer trips in 100 degree weather.

The Trail Plant Checklist

The Plant Checklist is currently available in two different formats:

Separate condensed print versions of just the checklist names are available for all except for the Calflora thumbnail picture version.

Go to:

Copyright © 2014-2016 by RT Hawke, Shaun Hawke, Tom Chester, Jim Roberts, Keir Morse, Kate Harper, Angelique Herman, Anne Kelly, Carla Hoegen, Fred Melgert, and Mike Crouse
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
Updated 5 April 2016.