“It’s so weird that plants can actually grow here”.
This phrase is expressed by the majority of people who visit Santorini for the first time. Indeed, the landscape of this island is unique and astonishing but the actual soil looks like a mixture of desert’s sand and lunar rock fragments. Actual soil? no sorry, this is not the real one. The original Santorinian soil (like in most islands of the Cyclades) was mainly consisted of limestone. But today we cannot really see any kind of limestone in Santorini apart from the top of Prophet Elias, the “tall” mountain with the monastery and the antennas on the top.
The rest of the island has been covered by multiple - multicolored layers of solidified lava and volcanic ashes. Everything changed in 1612 B.C.: This was an enormous explosion, one of the largest recorded volcanic eruptions in the history of earth. Thousands - if not millions - of cubic meters of lava were blasted in the sky and then, of course, it had to fall down and cover what was left from the original island. The atmosphere was cooling the lava on its way down and that’s how different volcanic rocks were formed. Therefore, today’s topsoil consists of basalt, volcanic ashes, sand, pumice stone and some other formations of lava, a mixture known as “aspa”. This aspa though is not the same across the island, it seems to differ significantly from place to place (so, are there any regions or sections that are much better than others within the island?)…
Anyway, how does generally this soil affect the way that grapes grow?
To begin with, Santorinian aspa is overall poor, infertile and dry. Surprisingly, it is rich in a few minerals: iron, Calcium and Magnesium exist in adequate - if not high - amounts. However, the soil is extremely poor in Potassium and this is a key factor for the Santorinian Assyrtiko, as it results in very high total acidity and significantly low pH levels (sometimes it gets as low as 2.7!) which is one of the fundamental characteristics of this extraordinary white wine. The organic matter is also very low and this one of the reasons (in addition to low clay percentages) why Phylloxera could not survive here. Phylloxera (Daktulosphaira vitifoliae, Hemiptera: Phylloxeridae) is a tiny insect pest (relative to Aphids) with a very bizarre and complex life-sexual cycle. It spends most of its life in the soil, developing huge populations as colonies on the roots of the vines and sucking juice from them. As a result of this, the roots of the sensitive European vines get deformed and vulnerable to secondary fungal and bacterial infections. Phylloxera apparently destroyed 99.9% of the European vineyards during the 19th century. But the vines in Santorini survived the disaster because of the soil!
Therefore, today Santorini owns some of the oldest vines in Europe (some of them are over 200 years old). The older vines tend to produce more concentrated grapes, so usually higher quality wines. For the same reason (no Phylloxera in the soil) there is no need for American rootstocks, so the vines here are ungrafted (American vines are resistant to the pest so they are extensively used as rootstocks). Ungrafted vines tend to produce lower yields but they remain productive for a longer period. Coming back to water and minerals, it is obvious that the vines in Santorini are struggling to survive no matter if they finally survive for centuries. The soil seems to drain fast, doesn’t retain enough water. No water also means no Nitrogen can find its way towards the leaves for photosynthesis. Water stress is currently considered as the next best thing in the global viticultural research. Grapegrowers reduce or stop irrigating at specific growing stages because stressed vines produce better - more condensed grapes.
Extreme water stress is just an everyday routine for the vines in Santorini.
They have adopted to survive in extremely hot-dry conditions. This pumice stone seems to do a bit of a magic as well. It is white so reflects the strong sunlight and works as a sponge to absorb a little moisture from the air. In the battle between Calcium and Sulfur, looks like Calcium wins because most soils in Santorini are Alkaline. Therefore Santorini is one of the few places in the world where a soil with a pH around 8.2 can result in a wine with a pH around 2.8! Santorinian white wines (the ones from Assyrtiko) are bold, robust, powerful, crisp and vibrant. I don’t know for sure if the distinctive sense of minerality and the salinity, which everybody is talking about, derive exclusively from the soil, they probably do but I cannot prove it. All I know for sure is that this volcanic diamond (the soil) definitely makes Santorini wines deep, clean and rich, displaying character and personality.
Dr. Evangelos Beris,
Adj. Professor in Viticulture & Oenology - Uni. Of West Attica, Athens
Director of Science - Estate Argyros, Santorini