Black Mountain Rare Plant Survey

Photo: Tom Oberbauer

By Tom Oberbauer, Botanist and Past President, CNPS-San Diego

Time was drifting by and the summer of rare plant surveys was getting close to the end. The season for surveys and the project financing were almost past in 2015. Margie Mulligan and I were originally supposed to visit the top of Black Mountain, northeast of Sutherland Reservoir, but other commitments prevented her doing it. So, Jim Rocks was interested and Margie made arrangements for us to contact each other. The result was that Jim was going to be able to drive and I would meet him at his office in the Clairmont/Mission Bay area.

I drove there quite early one morning, arriving by 7:30 am. We loaded into his Honda Ridgeline 4X4 and drove out through Ramona and up Magnolia Avenue and then down into Pamo Valley. The vegetation was not completely toasted because of one interesting July rainstorm, the remnants of a tropical storm. It dropped quite a bit of rain in a number of places in San Diego County including 4 inches in Ramona where it flooded some streets.

The plant that appeared to benefit the most from the July rain was Salsola kali (Russian thistle). It was green and growing profusely in all of the open fields. However, the rain would have also assisted the native chaparral shrubs and oak trees during a very dry time of year. The road climbed gently up into the hills north east of Ramona and then dropped down into an oak and sycamore lined canyon, shaded by the larger trees but providing a view of a narrow valley as it lay before us.

Pamo Valley is such a beautiful closed valley. A large cattle operation apparently leases the City of San Diego land, which was once proposed as a reservoir site. It could be a closed valley anywhere; a mini-rural community surrounded by mountains.

We drove down the road farther until we came to the turn off on the east side for the road up Black Mountain. It started out low but gradually climbed and climbed. The lower part of the road passed through what was mostly open coastal sage scrub habitat. It started out with vegetation dominated by Eriogonum fasciculatum (California buckwheat) and Artemisia californica (California sagebrush) after leaving the grassy, grazed valley bottom. The road was not bad except for a couple of places, but we jostled our way up. There were switch backs and hairpin curves as the road worked its way around a ridge and then a straight section as it passed on the backside of the ridge. Salvia clevelandii (Cleveland sage) began to appear as the substrate changed from regular granitic rock composed of tonalite and diorite to gabbro –black granite. The soil changed to the characteristic red color as well. Gabbro is composed of high concentrations of magnesium and iron that stunts the growth of shrubs and reduces the density of the plants, but some plants such as Salvia clevelandii can tolerate it better than other species and appear to thrive.

As a reflection of the increased rainfall due to elevation and topographic features, the vegetation began to be dominated by Adenstoma fasciculata (Chamise) but it still had elements of coastal sage scrub species, Eriogonum fasciculatum and Artemisia californica. As the road climbed, the chaparral became larger though still gabbro-influenced, which results in stunted and more open chaparral than regular granitic chaparral. The road passed around another nose of a ridge and into a moist oak woodland and then over onto the west side of the ridge with an exposed vegetation that was not of arge size but grew on rocky slopes.

After curving around a cove of an upper drainage, with oaks and apparently a spring, the road wound around a knoll and intersected with an old gated road that extended to the north through a series of large meadows and into the back or west side of Mesa Grande. However, that was not the direction we were taking.

Inside Coulter Pine grove. Photo: Tom Oberbauer

What was most interesting is that this intersection is the site of the first pine trees we saw that day, Pinus coulteri (Coulter pine). There were a few moderately sized trees and a really large one that appeared to have died recently. It was covered with dead red needles, the tree having died during the first couple of months of 2015, probably due to the drought. Other Pinus coulteri trees on the slopes to the east of the intersection were also dead but they were quite clearly killed by the fires of 2007.

The road turned to the south and then east while continuing to climb. Thousands of trees were killed here by the Witch Fire of 2007. A few seedlings grew in these areas as well, from seeds released by fire on the semi-serotinous Pinus coulteri cones. The spaces between the cone scales open with the heat of a fire and then the cones release bright orange-red seeds. The major groves along the road in this area were planted as part of the Penny Pines project that for decades was supported and still is supported to encourage pine growth. Penny Pines is a Reforestation/Forest Education Program sponsored by the Garden Club Members of National Garden Clubs, Inc., working with the USDA Forest Service and State Foresters throughout the US and its territories.

A fuel break had also been maintained around these planted groves, but it did not prevent the fire from killing the trees, or in fact, many of the trees may have already been dead beforethe fire, having been killed by this century’s drought.

The fire cleared the forest so that no adult trees now stand in the planted areas. Over the years the question has arisen about whether any pines naturally occurred on Black Mountain. When driving by, it is not so obvious if the pines were natural or planted on the slopes along the road. However, one look at a 2006 or earlier aerial photograph showing rows of trees in the area makes it clear that these pines were planted. Three major groves had been planted on the western slopes below the highest ridge. Most of the trees grew in that area for decades while they were not disturbed and before the recent drought set in. One planted grove had been removed after most of the trees died from the drought. It may be that the overall density of the trees was a little ambitious for the moisture and rainfall conditions that exist there.

After passing through this area, the road steeply climbed north with a sharp switchback and a hairpin curve before it reached the end of the ridge at another grove of Pinus coulteri. Though the weather was predicted to be hot that day, it was pleasant and cool where we were standing in the shade of old Pinus coulteri trees.

The presence of this last grove brings up a major question that has been in the minds of many for years since the Penny Pine program began. Were all the Pinus coulteri trees growing on Black Mountain planted or were there naturally occurring pines before the plantings occurred? There is too little documentation to verify if they were all planted or not. It has always been my opinion that the upper part of Black Mountain is a sky island. As such, the pines represent a period of time when pines were more widespread and connected from peak to peak. Sky islands are groves of pines and other higher elevation species and forests on higher mountains that are surrounded on the lower slopes of the mountains by chaparral and lower elevation vegetation. At the present time, we have a number of sky island peaks in San Diego County that support Pinus coulteri, including Corte Madera Mountain, Los Pinos Mountain, Black Mountain, Pine Mountain on the northern end of Rancho Guejito, the upper west slope of Rodriguez Mountain, Bucksnort Mountain and the San Ysidro Mountains north of Ranchita. Unfortunately, nearly all of them have been ravaged by fires in the last 20 years and the forests have become much diminished. There are technically other types of sky islands in San Diego County as well, including Whale Peak in the Pinyon Mountains in Anza-Borrego State Park and even the top of Villager Peak in the extension of the Santa Rosa Mountains. Of course, some could say that all our mountains are sky islands, with remnant forests surviving from the Pleistocene. However, the sky islands mentioned here are true islands with small isolated groves of trees.

We walked into the pines to the south to see what plants were growing here. These pines appeared to grow in a natural configuration. They were growing in random patterns along the ridge line, in shade producing groves and small clusters above the densest chaparral. There were also individual trees separated from the main cluster in locations that were far from the areas that were the focus of planting. The planted areas along the road were clearly defined. These trees were in a natural occurring pattern just as they grown on Los Pinos Mountain, Pine Mountain and, to a degree, Corte Madera Mountain. There appeared to be about 60 trees on this ridge- top location. The interesting thing is that when examining the aerial photographs prior to the 2003 fire, the number of trees on the ridge top have not changed very significantly and a large proportion of them survived the fire in 2007. There may have been 20-25 percent more before the fire, but they were always sparse and scattered and the fact that they survived indicates that the fire did not burn their area.

Common representative species of the grove area included Pinus coulteri, Ceanothus palmeri (Palmer’s ceanothus), Arctostaphylos glandulosa (Eastwood’s manzanita), Styrax officinale (snowdrop bush) Cordylanthus rigidus (bird’s beak), Adenostoma fasciculataEricameria parishii (Parish’s goldenbush) and a few Eriogonum fasciculatum.

The Pinus coulteri trees here are of good size, probably predating the trees that were planted. When looking at historic Google earth images, it was clear that individuals of these trees did survive the fire of 2007. Their resistance to the fire is another indication that they were likely naturally occurring there. The County of San Diego has a set of aerial photographs from 1927. I do not recall if they cover this area, but it would be interesting to examine them to see if they grew there at that time. There are fire lookout tower remnants about a half a mile north or 3/4 a mile to the north of where we parked.

Monardella hypoleuca ssp. lanata. Photo: Tom Oberbauer

We walked among the trees. In addition to the species mentioned earlier, common plants included Crocanthemum scoparius (Broom rush-rose) and Hesperoyucca whipplei (Chaparral yucca). The strong sweet minty scent of Monardella hypoleuca ssp. lanata (Felt-leaf monardella) was also present. Ceanothus oliganthus (Hairy ceanothus), Diplacus clevelandii (Cleveland’s monkey flower) and Salvia clevelandii were also growing in the area. Stipa coronata (Foothill stipa), a large perennial grass, grew among the rocks.

A pale swallowtail butterfly was flying by as we walked down. I walked down slope several hundred yards toward a large old isolated tree. On the slope, Rhus ovata (Sugar bush) and Hazardia squarrosa (Sawtooth goldenbush) were growing in the strong sun of the western slope. Ceanothus foliosus (Wavy leaf lilac) was also growing there. It is another gabbro species with unique distribution, not rare in San Diego County, but disjunct to the north. A few individuals of the beautiful bright yellow tulip-like Calochortus weedii (Weed’s mariposa lily) were still in flower.

Along the ridgeline, Horkelia truncata (Ramona horkelia) plants still had green growth. Horkelia truncata looks a lot like Potentilla (now Drymocallis) except it has white flowers instead of yellow and the stems and leaves have a very strong odor very close to that of Chamaebatia australis (Southern mountain misery). It is a greasy, musty mint scent that is unmistakable.

Frangula californica (California coffeeberry) and Pellea mucronata (Bird’s-foot fern) were growing near each other on the slope. The really nice thing was that Pinus coulteriseedlings were growing 2-feet tall, apparently reproducing from the adult trees that did burn in this area. Other montane species include Symphoricarpus mollis (Snowberry), Wyethia ovata (Mule ears) and Ericameria parishii (Parish's rabbitbrush).

Burned area of Penny Pines with little recruitment. Photo: Tom Oberbauer

However, the trees being only 2 feet tall seemed small to me since the fire had burned in 2007, 7 years before. I could have expected if they generated that year, that the trees would have been a bit taller. However, there is no guarantee that the trees germinated right away. There can be delayed germination in some trees, but not delayed too long, just a few years. Large patches of Monardella hypoleuca ssp. lanatawere growing in open rocks on the ridge top.

The goal was to find the Packera ganderi that had been found there before, so we headed north past the former location for the old fire lookout tower. All that was left of the tower was the concrete footings and the steel bolt bases that had been cut off. There was also a cluster of species of non-native plants in the area including Vinca spp. (Vinca vine) that was spreading but still somewhat confined. One Juglans spp. (Walnut) was also growing near there.

From the north side of the peak we could see smoke rising from a fire near Aguanga in Riverside County, though it looked like it was on the back side of Palomar Mountain. The two large meadows of Rancho Guejito were visible to the west. A turkey vulture flew by while we were there. It was a warm day but where we were the air was freshened by a cool east breeze. Haze filtered the view to the west.

I headed over to the north side, down the slope below the peak. The vegetation here was a mix of Acrtostaphylos glandulosaAdenostoma fasciculatum and occasional patches of Quercus xacutidens, the hybrid scrub oak. The habitat seemed to be almost exactly like the habitat on Potrero Peak that supported the Packera ganderi. I looked around extensively at the base areas of the Arctostaphylos in the litter openings just like those on Potrero Peak, but this one is a bit higher in elevation. However, I did not find any of the Packera remains like we found on Potrero Peak. It was puzzling to me. Band-tailed pigeons were perched in the trees as I walked back up onto the peak.

On the open slopes near the peak, other plants of note wereTrichostema parishii (Mountain bluecurls) and a huge Frazera parryi (Deer’s ears).

We gradually drove down the road, stopping at the major intersection with the road to the north. I walked to the west and Jim Rocks walked to the east. I mentioned already that a huge pine had died near here. I walked all around that location because it was near one of the digitized points where we were looking to verify for the Packera. I hiked all around the top of a large knoll that had a steep cliff to the west, but to no avail. This location had a good representation of Quercus agrifolia (Coast live oak) as well.

We kept driving down the mountain, stopping occasionally and checking for the Packera. We found more Horkelia truncata, which for a second gave the false impression of dried Packera. We also tracked Salvia clevelandii down the mountain to a relatively low location.

An interesting coincidence was that in one portion of the road that was located in the shade of an oak woodland, with a slightly wider road so two cars could pass, we encountered another vehicle. It was a forest service Ford Expedition that was being driven by Jeff Hayes, the Cleveland National Forest Planner and riding along with him were Will Metz, the forest supervisor, and Gloria, a biologist. What are the odds of that happening on the day that we went there?

Black Mountain, or what is sometimes called Big Black Mountain, is located in the east of the foothills and west of the true mountains. It is in a transition zone and because of its unique gabbro soil, it supports unique rare plants. While we did not find the Packera that time, I have no doubt that it still remains on this sky island in San Diego County.