Growing body of knowledge

“Our situation in South Africa is that we have a young fine wine culture with old geology,” said Dr Etienne Terblanche at Stellenbosch Wine Routes’ recent Terroir Tasting. “In Europe, it’s the opposite. They have a centuries old fine wine culture with relatively young geology.”

What’s the significance of that? Simply put, it’s that whereas the lines or easily applicable norms and rules of “this soil, that vine” work in Europe, the same criteria do not apply on the southern tip of Africa.

Terblanche is one of those rare creatures who can take complex scientific information, parse it and share it, making it comprehensible and easily digested by non-scientists. The approach to viticulture 20 years ago was totally different to what it is today, he said. Back in the late 90s and early 2000s the methodology was purely physical: to look at the soils, whether the aspect was north-, south-, east- or west-facing, the altitude and slope. “Nowadays it’s not so clean cut. We’ve realised that it doesn’t automatically follow that if you have ABC soil and slope, planting a particular grape variety will produce XYZ result,” he said.

There’s so much more to it – including the human and cultural element as well as an appreciation for variable climatic inputs. Terblanche then proceeded to synthesise the geology underlying the Western Cape’s soils, starting with the Pangea supercontinent 600-plus million years ago, explaining how and when the sedimentary soils and Malmesbury shales were derived, doing the same with the granite suite 200 million years ago and finally how the movement, intrusion, deposition and climatic weathering have contributed to the dirt beneath our feet.

“Now we sit with koffieklip soils in our valleys, weathered soils which are good for producing great wines – while soils mid-slope are vigorous,” he said. In Europe, the conventional wisdom is not to plant vineyard in the valleys because of the rich soils which have weathered from higher elevations. “They’re too vigorous – so the rule of thumb there is to plant higher up.”

In Stellies, it’s not like granite soils predominate in the north and shale in the south, for example. Europe is more cut and dried or distinctly delineated because their soils are geologically younger. “Here, mixed soils are everywhere!” And that’s where the viticulture becomes so crucial, considering rainfall, solar radiation and farming practices. An example he cited was the Polkadraai hills of Stellenbosch which felt the cooling effect of both Table and False Bay waters. “The area doesn’t quite get a full on fog such as that experienced in Sonoma, California, but there is a definite haze which results in decreased solar radiation but also increases humidity,” Terblanche said.

“This is an exciting time to be in research,” he said. “The challenge is to be able to take massive datasets available to us and to analyse and extrapolate results.”

All of that was a preamble to a tasting if four distinct flights of Stellenbosch wines: Chenin Blanc, Chardonnay, Pinotage and Cabernet Sauvignon to demonstrate the extensive work done by the Stellenbosch Wine Route and producers. The idea was to assess these wines, not to score or rate them, but to rather consider whether it was possible to distinguish differences in texture and mouthfeel which could be attributed to underlying geology.

- Blog by Fiona McDonald