I began with trail along the ridge top. It's open grassy fields, some, not all, covered in flowers. This sea of yellow coastal tidy tips offered the first mass display ... and an irresistible photo opportunity.

Another ridge area shot, this one from near the end of the day's hike, showing California poppies and hairy vetch. The yellow here is weedy hawksbeard, Crepis vesicaria, a non-native that was a little less common up top but more so on the lower slopes.

Impressive swaths of poppies and lupines too.

The landscape offers more features off the ridge. And in the morning, there was a defined cloud bank below as well.

More ridge views. Sky lupines in with the California poppies here. There might be an ocean down there someplace.

Just a bit later. The low clouds are rising.

Below to the east lies the bay. Dumbarton Bridge. Mt. Diablo.

Now let's look up close. Eschscholzia californica (California poppy) and Layia platyglossa (tidy tips). Most of the latter had all-yellow ray flowers, which I gather is more common near the coast.

Layia platyglossa (tidy tips), here with the white/yellow ray flowers. This coloring is more common inland, so we must at the overlap between coastal and inland forms. With California poppies, of course.

Poppies and Lupinus nanus (sky lupine). This could be Lupinus bicolor (miniature lupine) but I think I'm seeing the features that point to nanus: longer pedicels, clusters over 3" tall, leaves over 1/4" wide at their widest point, and a banner that is wider than tall. Still, none of these are *that* easy to see so I'm not 100% sure. With some common fiddlenecks (Amsinckia intermedia).

Sidalcea malvaflora (checker mallow). It's not one of the "big four" -- California poppies, sky lupines, tidy tips, and hairy vetch -- but a fair number of these were scattered about.

Layia platyglossa (tidy tips), up close. I would have expected the phyllaries to be less pointed. But what else would this be? Madia elegans sort of fits but it's early for them and the branching isn't right. They tend to be less "orderly" too.

Layia platyglossa (tidy tips) in their bicolor form, up close. Here with a reminder that much of the stuff other than the showy flowers is not native. Not the dogtail grass (Cynosurus echinatus). Not the little pink Erodium flowers with their long seed pods ("heron's bills" or "storksbills").

After walking the ridge almost to the north end of the park, I headed down the Hawk Ridge Trail ... as the low clouds/fog came in. Here I'm just short of the Alder Spring Trail junction. Grasses mixed more with flowers down here, but this was a colorful spot.

Crepis vesicaria ssp. taraxacifolia (weedy hawksbeard) is the yellow here. It's not native and certainly has that dandelion-like look common in old-world composites. I didn't include a picture, but the leaves look right too.

Achillia millifolium (yarrow) a few minutes along, now on the Alder Springs Trail. Not all is non-native.

Dichelostemma congestum (ookow) a few more minutes along, on what's now on the Charquin Trail. It's that time of year when the similar blue dicks finish and these arrive. Note the "waist" in the corolla.

Not quite to the Ancient Oaks Trail junction yet, but definitely in a forest of old oaks and bays now. And fog.

Fritillaria affinis (mission bells). Woodland flowers now for a while.

Maianthemum stellatum (starry false Solomon's-seal).

Trillium chloropetalum (giant red trillium), very near the Ancient Oaks Trail junction. This one's just finished.

Trillium chloropetalum (giant red trillium). This group, just a few minutes up the Ancient Oaks Trail, were still very much in bloom.

Adelinia grandis (Western hound's tongue), also on the Ancient Oaks Trail. Lots of these were in bloom, and that surprised me a little. In the East Bay, these all finished a few weeks ago. Formerly in the genus Cynoglossum.

Ancient Oaks indeed.