I've gotten a series of questions recently, mostly from people inside the trade, asking me some variation of the question "so, you're pretty far west in Paso Robles, right? That must mean you're cooler than a lot of those big eastside wineries."
Interestingly, it just isn't true that, in Paso Robles, east is hotter and west is cooler. Sure, the farthest eastern stretches of the Paso Robles AVA are usually hot, and stay hot later in the day than we do out west. But north and south make at least as much difference as east and west for temperature. To get your bearings, take a look at the map below (created with the help of the excellent interactive Paso Robles AVA map tool on the Paso Robles Wine Country Alliance site); click on the image for a larger, clearer one:
While we are close to the coast, the cool sea air is largely blocked from affecting us by the Santa Lucia mountains. Just a few miles south, in the Templeton Gap, cool air flows more freely through the gaps in the mountains and cools the vineyards there dramatically in the afternoon. I wrote in more detail about how this happens about a month ago in the post west Paso Robles wind flow, the Templeton Gap and the Adelaida climate.
The other effect of the dual flows of cold, often moist air (up the Salinas Valley and through the Templeton Gap) is to bring morning fog into the lower-lying areas, including most of the vineyards in the Salinas and Estrella River valleys. As this fog takes some time to burn off in the morning, summer days are often fifteen or twenty degrees warmer when I make it out to Tablas Creek to begin my work day than when I left my house in town. These dual effects (afternoon sea breeze and morning fog) in effect create four different climatic zones in Paso Robles. Areas in the Templeton Gap, which receive the earliest afternoon cooling and relatively late morning fog, are the coolest parts of the AVA. Areas that are relatively high in elevation north of the Templeton Gap but west of town (like the Adelaida area in which Tablas Creek sits) have a moderate climate, warming early in the day but cooling earlier in the evening. The average daily temperature in this zone is similar overall to areas close to town who warm later in the day but stay warm later into the evening. Finally, there are the areas relatively far east of town which don't get any significant fog but also don't get much cooling from the valley airflow. These areas are measurably hotter than the rest of the AVA.
Although the climate of the Adelaida area is not that different from that in town, there are three major characteristics that distinguish it. The first is soils, which in our part of Paso Robles are very high in calcium with little topsoil cover, forcing vines to work into the chalky bedrock for sustenance. The calcareous soils in west Paso Robles and west Templeton are among the largest in the state of California, and some of the only ones in areas warm enough to ripen late-ripening grape varieties like Mourvedre, Grenache and Cabernet. There are smaller calcareous deposits east of town, but in nothing like the same concentration.
The second distinction is rainfall. The closer to the coast that you go, and the higher up the coastal range you go, the more rainfall you receive. So, out at Tablas Creek (1500 feet elevation) we average nearly double the rainfall of the town of Paso Robles (700 feet elevation) and triple that of areas east of town. This means that producers west of town who wish to do so can farm without irrigation many years, creating grapevine root structures that delve deep into the bedrock in search of moisture. By contrast, irrigated vineyards reward the roots that stay at the surface, largely in the topsoil, nearer their primary source of water. We feel that the deeper root systems that are encouraged in our largely-unirrigated vineyard produce grapes that show more character of place.
Finally, the third distinction between east and west Paso Robles is topography. The land rises sharply once you leave the Salinas valley to the west, rising into wooded foothills cut by pocket canyons. East of town, gently rolling hills and broad plains extend nearly to the eastern edge of the Paso Robles AVA. The area east of town is unquestionably easier to farm, and most of the large plantings in the AVA have occurred there. These large plantings include parcels planted and managed by the larger wineries in the area (including J. Lohr, Meridian, EOS, and Robert Hall) but very many are planted by independent grapegrowers who market their grapes, by the ton, through a variety of long-term and year-by-year contracts. There is good reason for producers interested in producing at higher yields, whether to produce value wines or to maximize their tonnage per acre as a cash crop, to choose the east side of town. The steep hills of the Adelaida and Templeton Gap regions make mechanizing farming difficult and mechanizing harvesting impossible. The relative lack of groundwater on the west side makes irrigation a dicey proposition, while a plentiful aquifer under much of east Paso Robles assures a regular water supply. These two factors preclude us, and most other producers on the west side, from producing more than 3 or 4 tons of grapes per acre most years.
To get a sense of the differences in topography, compare the following two photos. The first is a shot taken at Tablas Creek, looking east at one of the larger (perhaps the largest of the) plantings on the west side, at Halter Ranch. You can see the relatively steep hillsides and the valleys within that can be planted to grapevines:
Compare that to the below shot of the rolling plains and extensive plantings of the Estrella River basin, included paradoxically by the Wine Enthusiast a few years ago in an article touting the potential of westside Paso Robles called "The West Side Story":
I think that much of the difference between the wines of east and west Paso Robles (that most people within and outside the industry ascribe to climate) can be better thought of as an example of topographic determinism. By that I mean that the producers who wanted to make higher-production wines to sell less expensively chose eastside Paso Robles because it just isn't practical to farm inexpensively west of town. And by doing so, they convinced many people that this was all their area was capable of. The producers who started west of town were forced to sell their wines more expensively because it was more expensive to develop and farm their land, and their land produced fewer tons per acre.
I'm not dismissing the impacts of soils and rainfall; we believed that both were important enough for what we wanted to do to choose the site that we did, far west of town in an area that at the time didn't have a vineyard within three miles. But I think that the terrific high-end wines being produced by eastside wineries, from eastside vineyards (but just starting to get noticed) will start to change people's opinions of the entire AVA. And this is why the plan for 11 additional AVA's within Paso Robles, still as of this writing being considered by the TTB nearly two years after it was filed, should in the long run help the producers east of town at least as much as those of us to its west.
I think that the rise of wineries making and marketing premium wines east of town is a great thing; the investments that these wineries will make (and have been making) to produce their premium wines in areas formerly thought suitable only for "value" wine production should result in a dramatic improvement in the reputation of the Paso Robles "brand".
And, perhaps even more importantly, a more sophisticated understanding of what the real differences are between Paso Robles east and west, north and south, hills and plains, and wet and dry, will help all of us match up the varieties we grow with the farming practices we implement and the land we farm.