Traverse Creek Botanical Special Interest Area
Key reason to go: To see serpentine vegetation. While there are several serpentine areas in the county, Traverse Creek is one of the prettiest and most accessible. It’s loaded with beautifully-mottled, dark green stone with smooth surfaces that are perfect backdrops for the bright pink lewisia (Lewisia rediviva) that is abundant on the brittle outcrops in April, and a nice variety of serpentine endemics.
Best time to go: Winter for ferns and exercise; April for lewisia and fawn lily, then again in June when there is a late sidalcea bloom (Sidalcea hartwegii or S. hirsuta, both are there), and July for tripod buckwheat (Eriogonum tripodium) and Congdon’s onion (Allium sanbornii var. congdonii).
Special plants to look for include the already mentioned lewisia (Lewisia rediviva), and both the mouse-ear and pansy monkeyflowers (Mimulus douglasii and M. angustatus), and fawn lily (Erythronium multiscapoideum). Check here for a plant list created by members of the El Dorado Chapter.
Directions relative to driving north from Placerville: Take Hwy 49 north and go about one mile to Hwy 193; turn right toward Chili Bar and Georgetown. Go down to the river, up the grade, then on a few miles past Kelsey. You may notice a road named “Traverse Creek” but do not take it! Instead, continue on and watch for the Christmas tree lot on the left, then a mile or so farther, you will see Black Oak Mine Road, also on the left. Shortly after you pass Black Oak Mine Road, turn right onto Meadowbrook Road and follow the road down the hill to the intersection with Bear Creek Road; go across the road and park. Check this Google map. (GPS Users: UTM Section 10, 4804 605 N, 689 346 E)
First, what is serpentine?
Serpentine is an ultramafic rock formed when pyroxene and olivine minerals under the ocean’s crust are forced up by plate tectonics and metamorphosed by ocean water and decreased heat and pressure into serpentine. Serpentine minerals are light to dark green, varied in hue, and smooth fractures feel slippery.
Basically, serpentine soils are not favored by most plants because of high levels of heavy metals (nickel in our area) and low levels of calcium, sodium, and potassium silicates. Some plants have adapted to this unusual mix and are even indicators of serpentine soils. Some other plants seems to be able to live on serpentine soils as easily as on “normal” soils, and that is why we like to poke around in the sertpentine soils of Traverse Creek.
“Vegetation on ultramafic soils takes the form of distinctive variants of conifer-hardwood forest, chaparral, or grassland. Often the serpentine vegetation is sharply delimited from adjacent non-serpentine types, both by physiognomy (e.g. chaparral on serpentine, forest on nearby nonserpentine), and by species composition.” —Arthur R. Kruckeberg, author of California Serpentine Soils.
Traverse Creek is designated as a Botanical Special Interest Area because of the serpentine soil. As is typically the case, an area (niche) that isn’t being used will eventually give rise to plants that find a way to adapt, taking advantage of reduced competition for survival. Today we have a variety of plants to enjoy that are specific to a serpentine environment.
When you get there, look around at the big picture!
Just arriving at Traverse Creek and getting out of your vehicle should be all the time you’ll need to notice the different qualities of vegetation at the margins of “regular” soil and serpentine soil. The pines, for example, are ponderosa pines (Pinus ponderosa) on the slopes coming into the area, but foothill pines (Pinus sabiniana) in the serpentine area.
Initially the area will look a little desolate. While the trees are sparse and the vegetation isn’t overwhelmingly inviting, there are special things awaiting you. And while this is now listed as an Botanical Special Interest Area, it also has a longer history of an area of special mineralogical interest. It has been gone over by rock hounds and gold prospectors who dug the holes which will become obvious as you walk the area. Long before that, the area was clearly of interest to Native Americans who collected acorns and processed them on-site; you might find rocky outcrops with obvious grinding holes. It is also an area frequented by equestrians who want to ride their horses on the nearby trails; an activity which is permitted. ATVs and dirt bikes are not permitted on the trails.
There are just a few trails available (this is not a huge area). A basic first trip would have you start at the parking area (Fig. 1), follow the big trail northward and then cross the bridge. After that you can easily follow a trail that climbs a bit up the hill (after another bridge crossing) and leads you back south, all the while you will be able to see the road around the area.
There is a wide parking area seen at the bend in the road; wander over into the big rocky stretch and look for the lewisia in that serpentine during April. Beyond that area is a ravine with a small stream; look under the buckbrush (Ceanothus cuneatus) for the fawn lilies (Erythronium multiscapoidium).
Many of the trees and shrubs in the area are either evergreen or persistent. The black oaks (Quercus kelloggii) will change color and lose their leaves, but there are “scrub oaks” that will give you something to puzzle over if you are interested in identifying plants. “Scrub oak” is a term used for a number of similar chaparral varieties of oak that are shrubby and have similar (at first glance)—and generally small—leaves. In this area expect to find leather oak (Quercus durata)—one of the serpentine endemics here—but also look for the spiny-leafed oak that actually is called scrub oak (Qeurcus berberidifolia).
Another plant you could look for at Traverse Creek is a jewelflower (Streptanthus polygaloides), a curious plant in the Mustard family (Brassicaceae). This plant has a distinctive yellow-green color (in this area anyway). Compare it with our common mountain version, Steptanthus tortuosus. It is a hyperaccumulator of the heavy metal nickel; this seems to be its defense against the common cabbage butterfly (Pieris rapae) the larvae of which attack other cabbage family plants. It may interest you to read research on this. Serpentine jewelflower has a tall (up to three feet) stem with small chartreuse flowers that make it a little hard to find—that is, until you first find it; then you will see it all over the place.
Walking the trails around Traverse Creek might have you brushing up against some shrubby trees with shiny, lanceolate leaves. That contact will get you a strong whiff of California bay (Umbellularia californica), an evergreen which has a pungent fragrance that—in small doses—will please most people. This is not true “bay leaf” as you find in the spice section. True bay leaves are from a Mediterranean tree known as sweet bay (Laurus nobilis). However, it is actually okay to use a leaf of our local shrub to season foods. California bay is usually a tree of stature, but in serpentine soils it grows more as a shrub. This plant is in the family Laurelaceae, and that leads to a couple of surprises: 1) the avocado is in this family, and 2) laurel leaves were the leaves used to crown athletes and scholars in ancient Greece.
There is another clearly identifiable trail that leads out of the parking area. For a short hike that will introduce you to the vegetation, head north on the trail and continue until you see the foot bridge. Go over the bridge and in another 100 yards or so, find the brown trail marker. Turn around and see that another trail doubles back and goes up a small rise toward some dead snags. From that point the one trail is pretty obvious. You will cross one more foot bridge but keep heading up the hill a bit and then level out. The rest of the trail is gentle grade up and down, lined with a continuing display of scrub oaks to keep you busy with an ID book, coyote brush (Baccharis pilularis), coffeeberry (Frangula californica ssp. tomentella), and more. It’s only a one-mile walk and you will find that you are generally never at a loss to see just where you are, relative to your vehicle. That said, there are several other trails for you to follow at your discretion.
If you are there in April and walk along the road toward the south end, watch for a curious little mimulus called chinless mim (Mimulus douglasii), so called because it has much reduced lower petals. This is not a rare plant, but it is a nice little find; in fact there are few places in El Dorado County where the flowers are reported. It is also found in Red Hills area near Sonora. There is another reason to ponder the little mim: the family name has changed from Scophulariaceae to Phymaceae, and Mimulus douglasii is a bit of a character: it can self-pollinate. The botanical term for self-pollination in flowers is cleistogamous.
In late April on into June, try to find the little pansy monkeyflower (Mimulus angustatus). It’s never been abundant but it may be hiding in the grass near the south end of the hill. It is a plant that grows only in California. All in all there are nine species of mimulus to find on the Traverse Creek walk.
When the main trail leads you back to the paved road, across from a ranch fence and just half a mile uphill from your start point, wander off to explore the open expanse of exposed serpentine across the road (the parking area has been blocked out with rip-rap to suggest that OHVs should stay out!) During the spring, this area is quite a flower show when bright pink lewisia (Lewisia rediviva) blooms are all over the shiny green rock, and evening snow (Linanthus dichotomus) is abundant on nearby sandy areas. You need to be there early to see them because they bloom at night (Get it? Evening snow?) and may close up by 10:00am. This display in itself is worth the trip, but there are many more flowers to see over the April through June season; Sidalcea hartwegii is especially nice in June.
In June of 2006, a new flower was noticed in the area! A species from the Carnation family (Caryophyllaceae), Dianthus armeria ssp. armeria; the common name is grass pink. A non-native flower, it seems to be just getting started at Traverse Creek with about a half-dozen plants along the road near the bridge on Bear Valley Road.
Oh, by the way…
If you happen to notice amazing amounts of Scotch broom (Cytisus scoparius) along the road to Traverse Creek, and then notice a surprising lack of broom at the creek, it is because of multiple “broom whacks” by a small groups of volunteers from the EDC chapter of CNPS. Attacking the invasive plants with clippers, snippers, weed wrenches, and handsaws has resulted in a definite reduction of broom plants, which had been taking over the Traverse Creek Botanical Special Interest Area.
Scotch broom is a weedy shrub that has been declared an invasive and should be removed when possible! This takes time because the seeds like to grow in disturbed soil, and weed wrenches (a device to grab the base of the plant and literally rip it up with lever action) disturbs the soil and actually prepares a bed for the next crop. Volunteers have been clipping and cutting when the plants are in flower, trying to get them out before there are seeds to pop open. Making return trips to clip again when the plants are stressed in late summer seems to be working.