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. We are very pleased to share his reflections on the natural history of the Mountain. Together with David Nelson, he wrote San Bruno Mountain: A Guide to the Flora and Fauna. The book was published by Heyday Books in November 2022 and can be purchased here.
Spring 2024
Let’s start by saying that this was a very wet year with consistent storm activity from December to early May. After a lackluster December we went from a total of 9.30 inches of rain to 27.78 inches by the end of April. May and June threw in 1.31 inches for a total of 29.09. I noticed in my database that a pattern emerged with two pretty good years before and after a fantastic year. Precipitation is rainfall plus fog condensation. We had two fantastic years, 2016-17 (36.22), and 2022-23 (37.10). From July 1, 2015 to June 30, 2018 we received 79.12 inches of precipitation. From July 1, 2021 to June 30, 2024 we had 87.61 inches of precipitation. Let’s not forget that the back-to-back years of 2019-20 (15.59 inches) and 2020-21 (10.96 inches) combined for a serious drought figure of just 26.55 inches over two years. Average rainfall for San Bruno Mountain is 20 to 24 inches per season so over two seasons that figure should be between 40 and 48 inches. That’s a serious deficit!
As I wrote in my winter 2024 Journal, about half the required precipitation of twenty inches caused the creeks to really get going. Things just got a lot sloppier at the beginning of 2024. With three consecutive very good to great water years behind us, it’s apparent that the water table is extremely high. In mid-April the headwaters of Colma Creek were still flooded and running with a couple acres of above ankle-deep water still present.
This spring was particularly awash in cow parsnip (Heracleum maximum) for some reason. This large, showy plant with leaves exceeding a foot wide in most cases seemed to be especially plentiful and majestic. A great number of Native nations used it as a green vegetable which was peeled and eaten raw and was sweet, with one caveat: It must be eaten before flowering otherwise it gets a funky odor. It’s not disgusting, just not appealing.
Spring brought the poison hemlock to life and with water-logged soils everywhere it hastened me to start my war with this plant along the upper Bog trail. I saw one really tall flowering plant down the hill from me as I was heading home. I thought to myself,” I’ll get this guy tomorrow.” Luckily I remembered the next morning to get that blooming monster so I hopped off the trail and in a few short minutes I pulled 183 out of the ground. That’s how it is with hemlock. A square yard could have thirty or more plants within it.
Our native Indian thistle (Cirsium brevistylum) is one of the most attractive thistles you will ever see. It differs from other thistles because its thorns are located on the edges (margins) of the leaf, not on the upper and lower surfaces. It is a tall annual or biennial, 5—10 dm, which sprouts from a taproot in a basal rosette that lies flat on the ground. The stem is branched near the top, and often appears cobwebby. The inflorescence is composed of one to several discoid purple flower heads that are located at the tip of the stem. It prefers moist conditions and you can see it on the lower Bog Trail and Summit Trail.
If you have noticed arroyo willow leaves that are either chewed or have green or bright red galls on them, you have discovered the work of two insect larvae that rely on this species of willow (Salix lasiolepis) for survival. The spotted tussock moth is responsible for the eaten leaves and I wrote about this critter in my autumn 2022 journal. Check out the prose and the larval photo. The galls on the leaves are a reaction caused by the Willow-Leaf Gall Sawfly (Euura pacifica—formerly Pontania pacifica), which is a tiny wasp and not a fly. The female deposits eggs into willow leaves through a saw-like ovipositor, and a gall eventually develops within the leaf between the top and bottom surfaces. This is a result of hyperplasia and hypertrophy of the leaf’s mesophyll, probably as a response to the wound made by the mechanical destruction of cells and chemical substances injected while laying the egg. During its five (male) or six (female) larval instars, the larva feeds on leaf tissue, and then enters a pre-pupa stage whereupon it emerges from the gall and drops to the ground. It then spins a cocoon where it pupates and emerges as an adult. There are several other wasp species that parasitize sawfly larvae, and those wasp larvae emerge from the gall. The gall then becomes recycled as a home for other small insects
Hawks and Ravens and Crows, oh my!
These next two paragraphs happened within a span of fifteen minutes.
While standing in the open area of the tallest of the three hills in the western part of the Saddle Trail, I witnessed an aerial battle of the shared concern that birds exhibit during nesting season. A Red-tailed Hawk and a Common Raven took turns being the chaser and the chased. I am familiar with both birds since they share territory around my house. The chases went on for about a minute when the hawk decided to land on a branch of a cypress tree. Of course the raven decided to take one last dive on the hawk before flying off.
As I was descending the trail about 600 feet from the hawk-raven episode, I heard several crows making noises and flying about in some young cypress trees. I also saw and heard several ravens doing the same. I couldn’t comprehend what was causing this excitement, but I noticed a smaller bird at the top of one of the cypress trees. I raised my binoculars to focus on the bird and it turned its head to the left and I saw a bright red eye on his black head—it was a Spotted Towhee! Towhees typically stay lower to the ground since they’re basically bush birds. And then it hit me, this towhee was a spectator, just checking out the verbal posturing between two species of potential nest robbers.
Up in the Great Meadow the gold fields (Lasthenia californica), Johnnie-tuck (Triphysaria eriantha ssp. eriantha) and common owl’s clover (Castilleja densiflora ssp. densiflora) were putting on a show for the third year in a row by blanketing the ground in yellow, white and red. On my April field trip I coaxed my participants to follow me on a walk around these carpets of wildflowers. On our walk down Radio Road we noticed some shrubs with fringed yellow flowers on them. The foliage smelled of crisp citrus. I took some photos and when I got home I set out to identify this shrub. It turned out to be fringed rue (Ruta chalepensis) which is in the Rue or Citrus family. It is related to oranges and lemons. Ruta is the classical Latin name for a rue plant, derived from Greek. The species chalepensis is a spinoff of halepensis, the Latin suffix meaning of or from Haleb, a city in Syria, and it is native to Turkey and surrounding areas. Fringed rue is a tall shrub that grows in crowded colonies. The flower is unique in appearance with four or five yellow petals with inrolled margins that appear scoop-like and fringed with fine long hairs, like a spaghetti scoop.
It has been a great spring season with gentle showers, lots of flowers, and sunny weather. It was also pretty windy in May and June. As we prepare for the typically cool foggy days of summer, let’s not forget that Buckeye and Owl Canyons, and Juncus Ravine should be sunny and warm.
See you on the Mountain…