Wine o’Clock News – Texas Terroir, Part 2

Last month we talked about the adaptive capacity that grapes have to hot weather by means of triggering Heat Shock Genes which generate certain proteins which make the plants able to not only withstand the heat but to succeed under it.

Now, we will compare the Hill Country weather with what might have been the sort of weather pattern back when those first civilizations of the Middle East decided to curb their nomadic ways and started cultivating a local fruit vine, the grape vine.

The oldest winery that has been discovered is located close to Areni, a small village on the Arpa River Valley in the Province of Vayots Dzor in Armenia, which shares the latitude of Kansas City. It’s a remote mountainous area that bears a rather extreme weather pattern as shown below (right) compared to a Marble Falls, TX weather station (left).

                         Marble Falls, TX                                          Areni, Armenia

Marble falls and Armenia

The red and blue lines show the long term maximum and minimum temperatures, respectively for both sites. The sizes are different so the horizontal lines are comparable to each other. The grey lines show temperatures for one particular year.

As we observe, winters in the Armenian area can be freezing cold with minimum temperatures falling in the teens in January, and then they go up fast to reach a 93ºF average for maximum temps for the months of July and August. As a whole, the Hill Country enjoys a bit warmer temperature all year round.

Another area known to have developed the grape vine as a crop was further south in today’s Iran. Actually, there were more than 300 wineries in that country until they were banned for political/religious reasons in 1979. Below, there is another comparison of weathers, this time Marble Falls with Shiraz in Iran, which is at the same latitude of San Antonio, TX.

                        Marble Falls, TX                                              Shiraz, Iran

Marble falls and Shiraz

In this comparison, we can tell that both places show a closer look of temperature patterns. Though Shiraz can have hotter maximum temperatures during summer, it seems to cool down more at night. However, plants growing in these environments can succeed if, and only if, they are fully adapted to their weather conditions.

Incidentally, University of Pennsylvania Professor Patrick McGovern, author of Ancient Wines and Uncorking the Past, told me that those weather patterns have not essentially changed since those early times.

To focus on our Hill Country weather and to show where we are located weather wise, the chart below shows Marble Falls (left) again, but compared to Napa Valley (right).

                         Marble Falls, TX                                          Napa Valley, CA

Marble falls and Napa

It is interesting to note that our winter gets a bit colder, but the cold period is shorter than in Napa, and then, of course, the Marble Falls summer temperature (maximum heat above 70, as an arbitrary number) starts in March and ends in November. The Napa chart shows 2010 temperatures (in grey) when there was a rather cool spring and summer and then, in late August they got a sudden heat wave that caused a lot of damage to the plant canopy and fruit which resulted in significant loses throughout a vast area. This is what happens when the plant is not prepared for those kinds of temperatures and they get hit by the heat. Instead, within an area of usual high temperatures, like Central Texas, plants get used to it and don’t have any effect from the heat, just like they used to do some 6,000 years ago where they were born.

So, have vines changed over the centuries? Maybe, but not at the rate one would imagine, as it is much slower. In fact, even though we cannot trace some of the oldest varieties back more than 1,000 years, it is well established that ancient grape growing techniques were a result of what those people knew about varieties and their characteristics. This information suggests those early grape growers were aware of the benefits of vegetative propagation (asexual way of reproduction), leaving little room for genetic change.

This information, combined with the fact that the adaptation to heat looks more like part of a structural gene complex than a small mutation, allows one to conclude that what we see today as a behavior in the Texas weather really is rooted long ago, back in time.

Sergio Cuadra
Fall Creek Vineyards
Director of Winemaking