May 1, 2017
Thistle Season is in full swing. Last week we had good groups out both workdays and finished thistling Upper Barberry Ridge. Big thanks to you hardy souls; it's gritty work. And, welcome to Max.
This week we are working on Wednesday only, 4pm at Siesta Gate. We hope to make a big sweep up from the Skyline Trail to Water Tank road below the AT&T towers. Please let me know if you can make it.
And please be aware that we are now working in and around Poison Oak. It can be avoided, but if you are super sensitive, please be careful.
Sunday, May 7th, is the Bringing Back the Natives Garden tour and many of us are involved. My garden here in Berkeley and Bob's (Sorenson) in Orinda are both on the tour this year. It's a free tour that features some 50 East Bay Gardens that use native plants; EBMUD is a sponsor. You all are warmly invited to come visit - you can Google it for details and directions. There is an online write-up for each garden.
This morning, I want to take you on a little tour of a special corner of Skyline Gardens, which features a scree of volcanic (rhyolitic) rock. It's right along Grizzly Peak Road, a southwest facing slope, and is probably the hottest overall place we have at Skyline. It contains an annual native that is found nowhere else at Skyline. The mix of plants there is also found in the same assemblage on the top southern slopes of Mount Diablo, on chert scree. So you might say we have a little patch of upper Mount Diablo (or Southern California) right here at Skyline.
Here's a map of the area:
The purple polygon marks the road cut slope right along Grizzly Peak Blvd. This is .4 mi south of Siesta Gate. (For some reason, on this map it's called Scott's Peak Trailhead??) There is a good turnout where you can park marked by the orange/blue "X". You can walk south along the shoulder about 50 yards to see the various patches. There is a lot of traffic there, so it's not a bucolic setting, but botanically it's thrilling.
Here's a picture of one of the road cut slopes, facing southerly. At the top you can see mixed scrub of Sage and Coyote Brush. Below that is a rock ledge, and then a wide, clear, tan-colored band. This band is the scree of a special kind of volcanic rock (rhyolite and perphaps ancient volcanic ash) that crumbles. This band is clear because over the last two years I have removed all the invasives here, leaving just the natives. Below this is a band of green which is 95% entirely trashy exotics.
Here's a closer look at a cluster of natives in that band:
There are six native annuals right in this cluster, which is about three feet wide. Such diversity!! Clockwise from the upper left we have: Arroyo Lupine (L. succulentus) a small purple flower; Graceful Tarweed (Madia gracilis) tall and green; Chia (Salvia columbariae) tall blue/purple spike balls; Wire Lettuce (Stephanomeria virgata) silvery, spidery spikes rising; Chilean trefoil (Acmispon wrangeliensis) low mat with yellow pea flowers; and directly to the left is, Wine-cup Clarkia (Clarkia purpurea).
Here is a close up of the Chia and Wire Lettuce cluster:
I just find it amazing that such a diversity of natives exists. The Chia grows only in one other place at Skyline, below the trail under the first outcrop.
The Wire lettuce is only found on this slope at Skyline. This plant is not well known. It is a member of the Dandelion tribe, and gradually sends up a spike that takes forever to bloom, usually in August. The flowers are a very lovely shade of shell pink, and here is a picture:
Thanks to Keir Morse of Calphoto for this picture. The flower stalks can be two feet tall, and are very wiry. At any time there might be 10 to 20 flowers in bloom.
In terms of restoration, let's go back to that open band of tan rock in the earlier picture. Earlier this year, it was solid green with invasives with a few natives tucked in. I simply removed the invasives. Next year, if we keep the invasives out, these natives will cast their seed about and begin to fill in the cleared area.
Here is an example of that, a Chia patch this year. Two years ago, there were about a dozen scrawny Chia plants in this photo area. I have cleared this spot now for two years running. Last year, there was a marked increase in Chia numbers. This year, with the perfect rains we've had and continued clearing, here is our Chia Patch:
Look, hundreds of Chia, a carpet of them here, in glorious abundance. This shot is right above the stone culvert.
Our method really works, and it is so gratifying. Not only are we bringing back the natives, which is worthwhile in its own right, but we are also creating a large and powerful seed bank for future years. And these areas could serve as a seed bank for repopulating native some of the degraded areas in other parts of Skyline Gardens - of similar slope and aspect.
If you go to the top of Mt. Diablo, and walk the first quarter mile of the North Peak Trail from Devil's Elbow to Prospector's Gap, you will find these exact same species growing together on southwest slopes of rocky scree. Think about that for a minute - isn't that amazing ... there and here. That's ecology!!
And, up on Mt. D, you will find a clover that we also have right on this same Grizzly Peak volcanic scree. I was finally able to make a positive ID of this one, which I found last year, weeded, and now the numbers are increasing. Please meet Foothill Clover (Trifolium ciliolatum):
This is a large, rangy - and beautiful- clover that can grow a foot across. The flowers are large for a clover, nearly the size of lawn clover. The plants have a succulent quality to them, and that makes sense, because they grow on these hot, scree slopes. The key features of the flower are: no involucre (leafy bract) under the flower head; and, if you look closely at the green sepals beneath each individual flower, you can see that the edges are fuzzy with little, threadlike .... cilia. So that's the origin of the scientific name, 'ciliolatum.'
I have also found this same species in Briones park, similar southerly slope, at the edges of Chamise/Sage Chaparral. That's ecology, again, the special niche for this species. It was once fairly abundant on sunny slopes, and was one of the preferred clovers for First Peoples in California.
We found another native clover this week as well. Our list is now at 246 native species. More on that next week.