Doug's Mountain Journal
A Chronicle of Natural History on San Bruno Mountain

Doug Allshouse has been writing his seasonal Mountain Journal for many years. It appears in the quarterly newsletters of the Yerba Buena Chapter of the California Native Plant Society (CNPS). We are very pleased to share his reflections on the natural history of the Mountain. Together with David Nelson, he is writing San Bruno Mountain: A Guide to the Flora and Fauna. The book will be published by Heyday Books in November 2022.

Winter 2022

“Someone finally paid the water bill,” said the bee plant to the buttercup. “Everyone looks so clean and crisp,” chimed in the milkmaid. And you know what? They’re absolutely giddy over the showers of October and December. Rainfall in October (6.96 inches) blew a big hole in the next wettest October (3.53 inches) which was in 2016. That rain year (2016-2017) ended on June 30, 2017 and was the wettest season in many years at 36.22 inches. Twenty to twenty four inches are about average for the Mountain. December added another 8.45 inches, the second wettest December since I started keeping records, bringing the season up to 17.94 inches. We are far ahead of the 2016-2017 year, however, January through April of 2017 received a healthy 24.22 inches of rain. As I wrap up this journal in late January we have been through a bit of a dry spell, which is not uncommon to our region.

All the water falling on and around San Bruno Mountain and the Guadalupe Hills eventually flows into the bay from two major creeks, Colma Creek and Guadalupe Creek. Guadalupe Creek has the shorter route to the bay. Its headwaters originate from the eastern side of Dairy Ravine and the deep south-facing ravines of the Guadalupe Hills. Several creeks in Buckeye and Owl Canyons and the quarry contribute to Guadalupe Creek, although not as directly as they once did before the mushrooming of warehouses along Valley Drive.

Colma Creek has a much longer and more interesting route to the bay from its headwaters north of the Day Camp. Much of the beauty of Colma Creek was destroyed when the four-lane parkway was constructed in the 1960s as an access and egress highway from proposed construction in the Saddle, a 300-acre area north of Guadalupe Canyon Parkway accessed at the main entrance.. Thankfully the San Mateo County Supervisors voted 3-2 to keep the Saddle as open space. Colma Creek empties into the bay just north of the airport. Today a good portion is buried through Daly City emerging just north of El Camino Real as a deep concrete culvert visible at several intersections in South San Francisco where it empties into the bay just north of the airport.

When asked what my favorite plant is, I have a conundrum, because there is a tie for first place. The answer may surprise you, and one may even disgust you: poison oak (Toxicodendron diversilobum) and creek dogwood (Cornus sericea subsp. sericea). My favorite two plants do not have really showy flowers, but they each possess the most fascinating leaves. Plus the bark and fruits are wildly different and extremely photogenic. I have more photographs of these two shrubs than any other shrub, forb, grass or tree on San Bruno Mountain. Winter is a good time to talk about creek dogwood since it seems to shine best in the dreary winter months.

In Elizabeth McClintock’s A Flora of the San Bruno Mountains published in 1990 by CNPS she wrote only this about its previous synonym Cornus californica: “No longer occurs at localities where it had been observed in the 1960s: along creek in lower Colma Canyon (eliminated by construction of Guadalupe Canyon Parkway). Not located elsewhere in the 1980s.” That’s a pretty dire description of such a lovely shrub, but perhaps it was her way of communicating the destructive results of construction of a hideous four-lane highway.

Her heart would soar today because dogwoods not only reappeared in Colma Canyon, but have established many communities along Colma Creek and the Bog Trail as well. The name creek dogwood is fitting since it does not wander far from creeks or stream beds, preferring to keep its feet wet. A beautiful flowering shrub, it is celebrated for its electric-red bark that intensifies during the winter months when it is pretty much devoid of leaves. It readily spreads by underground stolons (runners) to form thickets, and its root system retains soil so well that it is used in restoration to prevent soil erosion. The ovate to oblong leaves are opposite and vary from dark green when young to wildly-vibrant shades of yellow and red, often with dark brown splotches scattered about. The white 4-petaled flowers are small and in clusters that appear in the spring and may last until winter. From July through December small green fruits are produced that mature into smooth-faced white to cream drupes (fleshy fruits) with prominent dark brown styles. The almost mature drupes may have a bluish tint. Cornus is Latin for dogwood and sericea is Latin for silky, referring to the texture of the leaves. Dogwood is native to most of North America except for Texas to the Carolinas and the Deep South.

Poison oak (Toxicodendron diversilobum) is a highly variable, deciduous plant that can be a groundcover, climbing vine, small bush, large shrub, an entire thicket, or even a freestanding tree. Toxicodendron is Latin for poison tree. The leaflets, usually three but rarely five, may be shiny or dull, green, burgundy, yellow, or bright red. They may vary in shape and size, hence the name diversilobum, Latin for differently lobed. In the spring when the sap begins to rise, the new foliage is shiny and deep burgundy but turns to green when chlorophyll is present. The inflorescence is loosely branched with yellow to whitish-green flowers. The fruit is a small berry that is consumed by birds and other wildlife. When the plant runs low on water, the leaves begin to dry and turn fiery red, giving the landscape a fascinating look, and finish their cycle with a dull burgundy before they fall.

The California blackberry can bear a strong resemblance to poison oak with a quick look, but the easiest way to distinguish it is to look at the stem. Poison oak bark is tan and smooth, but the blackberry has fine hair-like prickles on its deep red stems. The sap of poison oak contains urushiol, an oily chemical that is capable of causing a skin reaction from mild to severe, including itching and blisters. The oil, even when encased in amber for millions of years, has caused a dermal reaction once released and rubbed on the skin. The sap was used by the Miwok to burn tattoos. Unfortunately for many of us, it is the most widely distributed shrub in California.

Unlike last year at this time when the Mountain was still brownish, the rains have refreshed the landscape and wildflowers are bursting out almost daily. The milk maids, bee plants, buttercups, poppies, wallflowers, red maids, miner’s lettuce, and checkerblooms are starting to show their stuff. The wallflowers, in particular, are quite numerous already, with more to come. A few manzanitas are still showy. You cannot start too early to enjoy the show.

See you on the Mountain….