Vitis californica.

I once said I wouldn't "clamber through a thicket" to get a closer look at Vitis californica: I lied.  This morning I did indeed find myself fighting through some riparian habitat to get a closer look at California's wild grape.  This rather sizable vine is growing on the western bank of the Napa River, just at the point where the Oakville Crossroad passes over the watercourse.
The vines become quite visible this time of year as the leaves begin to turn yellow.  There is a wonderful specimen, teeming with grape clusters, quite close to where I live that has climbed 12 - 15 feet up through a very accommodating tree.  However, the vine is on the side of an extremely busy road and there is no possible way that I could safely get out of the car to photograph it.  So I had to be content with this Oakville vine.  But because this vine was more accessible, I was actually able to taste a wild, California grape for the first time ever.  Yummy!

The wild bunch.

Growing across a few open-topped, gravel-filled steps next to Vinoland's crush-pad is a wild grapevine (and some blackberries).  The vine is not really wild, as it most likely originated from a seed of a cultivated variety that was processed in Vinoland and somehow managed to germinate in an untended corner of the property. 
So what is it?  Well, the berries are spherical, green and tiny - 7mm, 8mm tops - and oh so very tasty.  The vine has had no measurable amount of water since the last proper rain (in the spring), so that could account for the berries being so small.  The clusters are cylindrical with shoulders, but that alone doesn't help to identify this vine.  Looking at the cluster did however narrow the ID down to three varieties; Chenin blanc, Semillon or Viognier - all of which have made at least one appearance in Vinoland (along with Chardonnay, Gewürztraminer, Marsanne, Orange Muscat and Pinot grigio).  No, for that I needed to take a closer look at the vine's leaves.  An ampelography, observations of leaf characteristics, is the only reliable way to properly identify a grapevine, especially one that has been water-stressed all season.  And sure enough, the mystery vine's leaf gave the game away; "...mostly 3-lobed with wide U-shaped petiolar sinus and reduced lateral sinuses; medium-length, sharp teeth; slightly bullate surface; light to moderately tufted hair on lower surface." (Wine Grape Varieties in California, UCANR Publication 3419).  Drum roll...Vinoland now has a volunteer, self-rooted Viognier vine.
No pruning, no sulphur, no water, no love.  This grapevine is just doing it's thing.  I love grapevines.

The wild one.

Autumn is indeed settling in and the few deciduous trees we have around Napa are showing off brilliant hues of yellow, orange, and red. One star performer in this category that often fails to get attention is Vitis californica, the native California wild grape. This deciduous vine is not shy and is very conspicuous, this time of year, in it's encroachment upon other vegetation. In riparian woodlands, stream-banks, and swales you can spot this wild vine scrambling up the trees and shrubs that are capable of supporting it's vertical growth habit of up to 40 feet. V. californica is important to wildlife as it's vegetation provides shelter and it's grapes, which ripen quite late, provide autumn and winter food for Napa's resident critters and our winter visitors.
The native vine has been employed in California since long before the first Spanish Padres planted their mission vineyards. Indigenous people cultivated and ate the grapes and leaves, used dried vines to weave baskets, and made tinctures to be used as mouthwashes and as a treatment for diarrhea. Lovely!
Apparently, jam can be also made from it's grapes. I have never personally seen a cluster of V. californica grapes. I've only glimpsed these vines from afar, usually out of my car window, and have never really felt a pressing need to clamber through a thicket, and risk getting a bad case of poison oak in the process, just for a quick look-see. There are plenty of cultivated grape varietals here in Vinoland to satiate any desire I may have to get up close and personal with a berry. Besides, who am I kidding, I much prefer having Thud and Prince Charles take care of all my jammy aspirations.