In Search of the Mount Diablo Sunflower

Today’s Glimpse from the Field is another edition of David and Doug's San Bruno Mountain Rare Plant Alert emails, from February 27th, 2016. David Nelson and Doug Allshouse are on the Mountain every Saturday in their search for interesting, rare and endemic plants - this ongoing research is the basis for their upcoming book. Together they are writing "The Natural History of San Bruno Mountain", a long-needed and detailed natural history of the Mountain. The book will be published by the California Native Plant Society.

David Nelson, aside from being a surgeon, is a devoted Mountain Watcher and amateur botanist. Doug Allshouse is an expert on San Bruno Mountain flora & fauna who has studied the Mountain for 38 years. They send out regular SBM Rare Plant Alert emails to interested persons. David can be contacted at and Doug at Contact David if you would like to be on the SBM Rare Plant Alert List.

Note: The Helianthella castanea should be in bloom in 2-3 weeks, so head out to the Ridge Trail, bring a lunch, and enjoy a rare flower - it's in the CNPS Inventory of Rare and Endangered Plants on List 1B.2 (rare, threatened, or endangered in CA and elsewhere). The Mountain is bustin' out all over - so get out there! And for you aspiring botanists, let us know if you see something unusual - photos and location, please. - David and Doug

On Saturday we went out the Ridge Road with Mark Sustarich and Aaron Schusteff, in search of Helianthella castanea, the Mount Diablo Sunflower. We were planning on dropping off the road and heading far downhill, past the old cattle fence, to where we saw it at the end of last season, with Lech Naumovich. When we found them last year, they had long gone to seed, and the weevils had had their fun, eating all the seeds!

We had not gone far from the road when we spotted something that looked like Helianthella, but much higher up the ridge than we anticipated. Luckily, the plant that is the most similar to it, Wyethia angustifolia, was growing about 4 feet away, so we could compare the two. We studied it for a bit, were fairly sure it was Helianthella, and then were lucky enough to find two buds on a plant nearby. They had long phyllaries! It was the Helianthella!

In the photo, the first plants were seen at the spot marked 1, and by the time we dropped down to the fence line at 2, we had seen 52 separate bunches of Helianthella. The area where we found them is at least as wide as the distance from 1 to 2, extending far around the shoulders of the ridge. The areas where we had seen them last year are all downhill from 2, so these groups were new to us. We are going to refer to this ridge as Diablo Ridge.

We are not sure, but we think we saw about 4X as many plants yesterday as during the exploration last year. They were all over the hillside, in the open grasslands, not just near brush, as has been previously described.

Here is our summary of their differences, with some photos:

Blooms earlier
Leaves less hairy
Shorter flowerstalks
Leaves with minimal wavy edges
Leaves with petiole
Irregular phyllaries
Seed compressed

Blooms later
Leaves more hairy
Taller flowerstalks
Leaves with wavy edges
Leaves without petiole
Uniform phyllaries
Seed not compressed

In the comparison of the leaves below, notice how the Wyethia has essentially no petiole, but the leaf blade extends to its base. The Helianthella clearly has a petiole, and in the field it is easy to see and is several centimeters long. It may be the most easily distinguishing feature in the field. The young Helianthella leaves have rounded tips, but the more mature ones were more pointed, so we feel that tip shape is not a characteristic. All the Wyethia leaves were pointed.

Comparison of the hairs (actually, cilia) on the leaves. The difference is easy to feel as well as easy to see with a 10X loupe. The photo might be about 30X.

Comparison of the hairs (actually, cilia) on the leaves. The difference is easy to feel as well as easy to see with a 10X loupe. The photo might be about 30X.

The irregular phyllary has always been a key feature distinguishing the Helianthella. Below is a view of two buds we found Saturday. On the upper bud, three phyllaries can be seen extending from the bud.

Aaron reviewed for us what a phyllary is. For those of you who, like me, need a review of flower parts, here is what I read when I got back. Below is a drawing of a simple flower from Howard McMinn's An Illustrated Manual of California Shrubs, which has some of the most beautiful black and white illustrations and has always been my favorite. I have colorized it:

As Aaron pointed out to us, the flower parts in a simple flower are arranged radially, with the sepals on the outside, then the petals, then the male parts (stamen: anther and filament), and finally, in the center, the female parts (ovary, style, and stigma). The key to remember is that the sepal is the part on the outside that protects the delicate petals during the bud stage.

thistle flower with phyllary and pappus pointed out

thistle flower with phyllary and pappus pointed out

The situation is different for a compound flower, like the Helianthella, where the petals are grouped together. The petals, as a group, are instead protected by the phyllaries. The pappus in a compound flower functions the same as the sepal in a simple flower.

David and Doug - see you on the Mountain!