Reference – Dr Ashton Senior Scientist – Land, Hawke’s Bay Regional Council. With all the talk that goes on about this great wine-producing region of ours, we went on the hunt for some information about a specific term we have all heard but some of us don’t really understand. David sought the help of Dr Ashton Eaves from Hawke’s Bay Regional Council with what the term terroir actually means.
You may have heard that Hawke’s Bay is one of the 12 Great Wine Capitals of the World. This is indeed a great honour to have bestowed upon us. Hawke’s Bay is home to the widest range of tertiary viticulture and wine qualifications in the country and is a widely recognised farming, agriculture and horticulture powerhouse, leading production for many of the country’s fruit and produce, and exports. Hawke’s Bay has more than 25 different soil types and ripens over 38 wine varietals.
We sought to understand, in everyday language, how we got here and what this means in our wine industry. And what exactly is a terroir? We discovered quickly that our climate and soil types play a big part, so we tasked our knowledgeable soil expert to please explain.
What makes the soils of Hawke’s Bay generally so good for growing things like grapes, pipfruit, stonefruit, berries and vegetables? We have to go way back in time to set the scene. Fundamentally, it is the complexity ofparent material deposition by air or water that has led to great loams (the way a soil is composed) for plant growth, particularly on the Heretaunga Plains.
Over geological time, loess (windblown deposits of fine sediments) blew in on the westerly winds some 14,000 years ago, during the last ice age. Subsequently, volcanic ash was deposited, either by wind or erosion, from greater than 10,000 years ago until the more geologically recent Taupō eruption of 150 AD.
Given the confluence of large river systems on the Hawke’s Bay plains, fine sand has continued to be deposited on flood plains. This sand is comprised of greywacke (a dark coarse-grained sandstone containing more than 15% clay), sandstone and red metals (commonly these metals include copper, brass and bronze) along with small amounts of limestone, volcanic ash and pumice eroded from the Kaweka and Ruahine Ranges. Meanwhile the Tukituki River has deposited deep clay sediment on the plains derived from the Waipawa area.
Stream and riverbed migration have continually mixed alluvial and windblown deposits. Alluvial soil is a soil composition made up of loose soil or sediments created by precipitation erosion. It is often composed of microscopic silt and clay particles and larger sand and gravel particles. Historically, many areas on the plains would intermittently become swamps until drainage was established in later years. This composition has led to naturally slow soil permeability with high organic matter, providing enhanced water availability to plant roots. This is a good thing and sounds like the outcome of a perfect storm, a storm that lasted a few years.
Is it just about nutrients or is it a combination of that and the make-up of the soil types? No, it is not just about nutrients as soil structure, organics and climate play a pivotal role. Versatile or ‘high-class’ soils make up only approximately 5.5% of New Zealand’s soil, of which Hawke’s Bay has a significant proportion, meaning food can be grown more cheaply here. Versatile soils are good for supporting rapid growth, by enabling the uptake of nutrients, water and oxygen given their special qualities of deep, free-draining, moist, fine-textured loams with rich organic topsoil.
Stoniness, aggregate size distribution and stability, and bulk density are also influential. Climate and environment are important: from adequate rainfall, high sunshine hours and mild winters to geographic features such as low elevations, easily managed slopes and a predominant north-easterly aspect (particularly the Heretaunga Plains). There are a few elements here that must be present at the right time and in the right proportions.
What is terroir? Terroir is a French word meaning soil or earth. It is pronounced ‘tear-wah’. In general, it translates to ‘a sense of place’ and in the wine world this means the combined influence that the soil, sun, wind and climate have on the growth of the grape and the finished product.
The French, especially the Burgundians, assert that terroir is an essential element, possibly the most essential element, in any wine worth its salt. They believe that if the finished wine does not express the essence of the land that gave it birth, then it is at best a soulless product, one that can only be tolerated and never thoroughly enjoyed.
Hence the crux of the great terroir debate. Is it the land that produces truly fine wines? Or is it the skill of the winemaker in taking the produce of the land and working their magic with it? In Burgundy, the Mecca of carefully nurtured ‘terroir wines’, grape growers will certainly choose the former.
The other side of the terroir debate is the view that great wines are crafted by the hands of creative and skilled winemakers, not simply sprouted from the chalky hillside of some obscure European village. While it is true that we cannot make great wines with poor grapes, many would argue that it is possible to make great wines from a variety of sources, including other fruits and vegetables.
Unfortunately, unlike sugar, acid and oak, terroir is not one of the components of a great wine that can be adjusted at the hand of the winemaker.
Who else uses terroirs? Wine is not the only crop that considers terroir. For example, cacao is grown throughout many regions of the world. Because of terroir, you’ll find that some cacao reflects fruity notes once it’s turned into chocolate, while others are deeper and more robust tasting. Even if the same cacao variety is used with the same growing practices, the geographical conditions of the region will affect the taste of the cacao and, therefore, the chocolate.
It’s also found in the milk that comes from animals because of the grass they eat. Terroir can also come from ageing processes, like cave-aged or bacteria-injected cheese varieties.
People refer to the terroir of the Heretaunga Plains as being special for grape growing and wine production. What is it specifically that makes it so? Ironically, gravels around Gimblett Road were previously referred to as among the poorest soils in the country, but they are now highly prized for viticulture. These have good drainage yet, on average, have a suitable available water capacity for grapes. This allows the roots to access water at depth in otherwise barren and dry areas that are also prone to wind erosion. It is a very recent alluvial formation with the soil profile having sand, silt and clay right where feeder roots take up residence, while tap roots seek deeper alluvial soil.
Our climate also plays an integral part in our terroir; days are not too hot given cooling sea breezes, which mimic the climate of Bordeaux, from where many of the grown varieties derive.
Are there other things that make the land here special? Other significant influences are climate and the local economy. As mentioned earlier, the slow permeability of rainfall is one key to success. It satisfies the plant roots for short periods, providing much-needed oxygen, while in general not stagnating or destroying the plants.
Mild winters, when compared to the New Zealand average, prolong the growing season, allowing growers to take advantage of spring and autumn rainfall, enabling some to produce multiple crops per year. This also means you can grow more veges at home for a longer part of the year, compared to, say, the South Island.
So, Te Matau a Māui is a special spot on the universe, was appropriately called the ‘Fruit Bowl of New Zealand’ and is clearly entitled to be one of the twelve winegrowing capitals of the world. When it comes to winemaking, we may be young in terms of our history, however we are quick learners and can pack a punch with our peers, who had a few hundred years’ head start.
