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To begin it is worth remembering that the great wines of the world are made in environments where the most naturally adapted grape varieties just reach full maturity. If the vines ripen too quick, too easily, at warm times of the year, then the wines just lack that something special. If they ripen too late, or in fact fail to ripen, the wines can range from thin and light to downright awful! So it’s a fine line if one wants to aspire to great wine and the joys of achievement are regularly buffeted by the tears of the years that didn’t quite make it. That is something that the vigneron and wine drinker must both expect and deal with. It is very obvious though that the smart producers in these fine wine areas have been very successful with “terroir manipulation” to reduce the number of “off vintages”; classed growths in the Medoc being a prime example.

So where does Hawke’s Bay sit? In general the Hawke’s Bay region is climatically slightly cool for making red wines from the ‘Bordeaux’ red varieties and Syrah. There is generally enough warmth for the vine to ripen the fruit for its own capacity, however the wine style requirements demand more heat at certain times of the day and season. The spring and autumn in Hawke’s Bay are certainly warm enough to ripen these varieties, however it is the lack of real heat during berry development that is the limiting factor. I sort of stumbled across this idea when doing my MW thesis in 1995 where I managed to categorise the regions of the wine world according to wine style by comparing, from fruit set to harvest, how hot it gets during the day alongside the total amount of heat available to the vine to ripen grapes, that is day and night-time temperatures. This neat little piece of maths gave a meaningful wine style perspective on the world of wine. ( Smith 1996 )

The cause of this lack of real hot summer days is the influence of the sea, which is less than 15km away for most vineyards, and generates a cool sea breeze from about lunchtime on most summer days. While the closeness of the sea makes us good yachties, its not really that great for getting those hot summer days needed.

From a wine style perspective, even for the intermediate climate loving ‘Bordeaux’ red varieties, it seems that daytime temperatures from fruit set until harvest have got to average 25°C. On a macro-climatic scale Hawke’s Bay does not quite fit that picture, and in cooler years the wines show some of the tears we were talking about. However within the region there are warm spots that in most years get very close to those fine wine regions climatically. When combined with a desirable soil type and some smart terroir manipulation using viticultural management, we can then justifiably say that our “terroir” has the potential to fit alongside those other producers of high quality Bordeaux red wines and Syrah.

The GIMBLETT GRAVELS WINE GROWING DISTRICT is one of these “hot spots” of Hawke’s Bay.

The GIMBLETT GRAVELS WINE GROWING DISTRICT enjoys a unique interaction of climatic and soil type factors that are shared with no other locality of the Hawke’s Bay region. It is a classic interaction of above ground and below ground environmental factors, that if one was present without the other the beneficial attributes of either would be negated entirely. In the views of the members it is this unique interaction that gives the GIMBLETT GRAVELS WINE GROWING DISTRICT its potential to become an internationally respected consistent producer of high quality red wines specifically from the ‘Bordeaux’ varieties and Syrah.

Mother Nature has given the GIMBLETT GRAVELS WINE GROWING DISTRICT some potential, however it is the manipulation of these “environmental terroir attributes” that will release the district’s full potential. Viticultural techniques in particular play a big part in maximising the vines potential. The environment is such that without significant human intervention not a single vine would produce grapes within the majority of the region.

The GIMBLETT GRAVELS WINE GROWING DISTRICT embraces the holistic view of terroir, it is not just the environment but, to borrow a term of Matt Kramer’s, of Wine Spectator Magazine, there is certainly a ” mental aspect”. The human heart and hand plays a significant part in releasing the potential of our environment in the GIMBLETT GRAVELS WINE GROWING DISTRICT, as it does in all the great wine growing terroirs of the world. We have talked about potential, time will tell whether we earn a place in amongst the respected elite of the world of wine.

It’s Hot Baby!

While the GIMBLETT GRAVELS WINE GROWING DISTRICT maybe slightly dryer than other localities within Hawke’s Bay during the summer and autumn the major climatic factor is, in fact, air temperature. The amount of sunshine varies little across the region.

What really matters is how hot is gets in summer, simply put for us we need the warmest sites possible. Without getting into the physiology of the vine and grape quality we need to ripen the grapes earlier in the warmest conditions possible. If that happens every aspect of red wine will be better. And that means to produce high quality wines from the Bordeaux red varieties and Syrah the mercury needs to hit at least 25°C during the summer more times than it doesn’t, and summer nights need to be warm enough to keep the vine working. Growing Degree Days during berry development need to be above 1000.

Many parts of the Hawke’s Bay region may be slightly cool for the ripening of the ‘Bordeaux’ varieties and Syrah. Unfortunately these varieties are still planted in some of these localities. GIMBLETT GRAVELS WINE GROWING DISTRICT has enough summer heat to do the trick in most years with maximum daytime temperatures between 2°C and 3°C warmer than many other viticultural localities on a classic Hawke’s Bay summers day. Significantly these high temperatures are reached earlier in the day and last longer into the evening. On cooler, cloudy days there is very little difference between the GIMBLETT GRAVELS WINE GROWING DISTRICT and other localities during summer except slightly higher night temperatures. Also in vintages where the whole region experiences hot dry conditions, such as 1998, the GIMBLETT GRAVELS WINE GROWING DISTRICT is still significantly warmer than other localities. However the effect on the wine may not be as great as in more normal years such as 1999 as these normally cooler localities have reached the 25°C base required in warmer years such as 1998.

The higher temperatures are due to an interaction between the districts sheltered location some 15km from the sea where the sea breeze is significantly warmer; its relatively low altitude of only 30m above sea level; the south-westerly shelter of Roys Hill; and, very importantly, the soil type.

How does soil type affect air temperature? The gravely soils warm up early in the spring, dry out rapidly and act as a big thermic blanket under the vines of the GIMBLETT GRAVELS WINE GROWING DISTRICT with soil temperatures at 30cm below ground level being some 5°C higher than other localities. Warm soil temperatures have a direct impact on hormonal triggers in the vine during ripening, nice warm soils in climates such as ours giving the most desirable effect. This thermic blanket also releases heat in the evening to the surrounding air, meaning the air temperatures stay warmer throughout the night sometimes into the early hours of the morning.

Even with these higher temperatures the GIMBLETT GRAVELS WINE GROWING DISTRICT still only reaches the bottom of what we regard is a desirable maximum daytime temperature for producing high quality wines from the ‘Bordeaux’ red varieties. We rely on terroir manipulation to get us right into that zone in more years than not!

Having said that however, when viewed over a 24hr period, vines in the GIMBLETT GRAVELS WINE GROWING DISTRICT receive significantly more heat than other localities, that is not adequately represented by the standard climatic indices of maximum and minimum temperatures and growing degree days. We believe this is an important factor in the GIMBLETT GRAVELS terroir without having any scientific basis for the opinion. There’s something to be said for the gut feel of a farmer, and that’s all we are, fancy farmers! Maybe the proof is in the wines.

There are likely other sheltered localities within the Hawke’s Bay region that also have these warmer daytime maximum temperatures, however the GIMBLETT GRAVELS WINE GROWING DISTRICT is the only area where this occurs in association with the gravely soils. Sheltered sloping sites in the Havelock Hills and around Bay View have proven to have equal ripening capacity to the GIMBLETT GRAVELS WINE GROWING DISTRICT . And of course in the hot vintages such as 1998, many localities in the region are able to ripen these varieties fully.

It’s all in the lack of dirt!

Soil is a key terroir factor mostly because of its influence on the amount of water that is available to the vine through the season, and how the vine gets it. In the unirrigated Old World mother nature is the entire determinant of that. In the New World irrigation often plays an important role dependent on what the vine can do by itself.

The soil, or lack of it, is a very significant factor in the terroir of the GIMBLETT GRAVELS WINE GROWING DISTRICT. The soils here are so stony that in 1988 an internationally owned concrete company purchased almost 25% of what is now the total planted area of the district and applied to mine it for gravel! If it wasn’t for a great legal result by winegrowers, now members of this society, a good part of this land may have been used to make the road that you travel on to get to Hawke’s Bay!

The GIMBLETT GRAVELS WINE GROWING DISTRICT was in 1867 the Omahu channel of the Ngaruroro River i.e. it was under water! At that time the river, as its velocity slowed, was dumping all the heavy bits (gravels and heavier sands and silts) around Roys Hill, with the lighter bits (silts and clays) dumped on the larger expanse of the Heretaunga Plains because they stayed in suspension of the river longer. That is essentially why the only significant area of these gravely soils is found around Roys Hill in what is known as the GIMBLETT GRAVELS WINE GROWING DISTRICT. The soils are appropriately called the Omahu Gravels.

Basically these soils are made up of gravel as deep as you want to go. The gravels are formed from compacted sands called greywacke who began their life under the sea some 200 million years ago. They were thrust out of the sea about 5 million years ago to form the mountains that are the backbone of both islands. The forces of nature split lumps of rocks off these mountains and the rivers transported these lumps to the plains, on the way breaking the big lumps into small lumps varying in size from a toenail to a football. These rocks are known as greywacke rocks. The process also created lots of smaller bits of sand, silt and clay.

The soils in the GIMBLETT GRAVELS WINE GROWING DISTRICT are essentially pure gravel beds with lenses of sand, silt and clay at various depths. These lenses contain up to 20% silt and 9% clay and along with the 10-40cm of topsoil present, is where all the feeder roots are located. Basically a vine, if given an unimpeded path, will send a tap root down until it finds one of these lenses and then send out the water and nutrient sucking feeder roots for sustenance. Having said that it has to work for it as these lenses are often few and far between.

The soils are naturally low in fertility and there is no particular mineral contribution from the soils or rocks. Unusually apart from regular applications of basic nutrients including lime, magnesium and phosphorous these soils seem to require minimal amelioration with fertilisers over the long term.

These coarse textured, weakly structured soils are very free draining and have very little water holding capacity, mostly between 9 and 20% soil moisture. In combination with the low summer rainfall, the soil is unable to provide the vines with enough water for them to survive, let alone produce grapes. Irrigation is necessary in nearly every vineyard, and is mostly applied as carefully controlled drip irrigation. Without the water there would be no terroir expression as there would be no living vines! While some commentators and producers endorse the attributes of dryland farming, we endorse the “use it don’t abuse it” philosophy on irrigation that significantly benefits wine quality and keeps the vines alive! With most modern research indicating that it is the effect of soil texture and structure on the hydrological properties of a soil that most determines the terroir influences of soil, the soils of the GIMBLETT GRAVELS WINE GROWING DISTRICT offer exceptional influence on vine performance, manipulated or not. More on that later.

Initial conclusions from a PhD thesis yet to be published by Mr Dejan Tesic, who researched viticultural environments of the Hawke’s Bay region, has shown that the “soil factor”, an interaction between soil temperature, soil moisture, soil texture and rooting depth, had a significant effect on vine performance. Those sites with high soil factors showed earlier flowering, veraison and harvest dates. Higher sugars and phenolics and lower acidity. Soils with the lowest soil moistures and highest soil factor scores produced the best wines. The sites with the highest soil factor score were the GIMBLETT GRAVELS WINE GROWING DISTRICT, and those with the shallow pan soils only in the driest years. These shallow pan soils occur around Havelock North and on the gentle slopes adjacent to the Tukituki River.

While some small parcels of these gravely soils are found in other areas in the Hawke’s Bay region, generally these localities don’t share the same climatic benefits that the GIMBLETT GRAVELS WINE GROWING DISTRICT does.

What the hell is “terroir manipulation” I hear you say? I first used this term back in 1998 at a seminar I gave on Sauvignon Blanc. Its based on the theory that for any terroir to express itself human intervention must occur. The great terroir’s of the world do not express themselves without intervention from the human hand, and more so the heart. French appellation law in many cases prescribes how you can manipulate terroir by things such as yield management and pruning technique yet strangely enough does not allow irrigation. In some seasons, even on those very clay rich soils, even these great French terroirs would make better wine with irrigation used scientifically and with the wine in mind.

In the GIMBLETT GRAVELS WINE GROWING DISTRICT , terroir manipulation is part of the vignerons art. Without irrigation vines would simply die without producing a grape on most of these sites. We have no clay for holding water to speak of. With the modern, scientific winegrowers approach to irrigation, we can measure very accurately how much water is available to the vine and give them just a little bit to get through the next day or so. They are literally drip fed. In this way we can produce smaller crops than on deeper soils with smaller berries having more flavour, colour and better riper tannins. We can even have a bit of a choice in this effect depending on the time of the season we give our vines this slight strangulation. All of this creates low vigour vines, which when combined with the significant crop thinning that now takes place, advances ripening by sometimes up to 10 days making up for some of that heat that may be lacking in some years. Remember this cannot be done on those deeper soils without the stones or those soils unable to control water availability.

I believe the biggest effect of these low vigour vines is on exposing more fruit to the sun. Now for a bit of vine physiology, if you can understand this then you will understand a lot about our terroir manipulation in the GIMBLETT GRAVELS WINE GROWING DISTRICT. Remember we need to get warmer grapes, not vines, to get into the climatic zone with all these great regions. For us, warmer grapes mean less herbaceous characters, more colour, more extract, better tannins, less malic acid. For us its what we want. We can get grapes warmer by putting them in the sun. Basically a berry in the shade of a canopy on a 22°C day will be at 22°C, below our desirable 25°C. A berry in the sun on a 22°C day, particularly after veraison when its got a bit of colour, will be at or over 30°C, well above our desirable 25°C. By irrigation and probably some leaf plucking we have manipulated our vine to think its in a terroir that is hotter than it really is. We’ve manipulated the terroir! This explains when you go around all the good producers in the GIMBLETT GRAVELS WINE GROWING DISTRICT that you see a lot of grapes in the sun very early in the season. Many even want to bare all and lay their fruit naked and exposed to the sun for all to see. Who said only Pinot Noir could be sexy! It also explains when you go to regions with much higher maximum temperatures than the GIMBLETT GRAVELS WINE GROWING DISTRICT , such as the Napa Valley, you see less grapes in direct sun because if it gets too hot they will produce jammy one dimensional wines with unstable colour.

These are two examples. A look at the viticultural techniques in the GIMBLETT GRAVELS WINE GROWING DISTRICT  will see variations on the same theme of giving the vine a fright and getting those bunches in the sun. Row spacing, vine spacing, clones, rootstocks, yields and picking strategy all have an effect. When you put all the permutations together you get a complex melange of contributions to wine style that help the GIMBLETT GRAVELS WINE GROWING DISTRICT area in producing truly ripe fruit from these varieties. This modern terroir manipulation approach has really only been in play for less than five vintages on vines of which very few are greater than ten years old. One might imagine what will happen when the vines get older.

Most vignerons practise these techniques in all their vineyards in Hawke’s Bay. In the Gimblett Gravels  wine growing District we are lucky we start with the natural state of our terroir being closer to the ideal . . . those higher temperatures of air and soil, and our soils with little water and their electric blanket effect at night, give us just a bit of a head start which we believe is critical.

This is our special terroir and how we make the most of it. Our art as vignerons is matching the terroir manipulation to the vintage, second guessing but still respecting what mother nature will do and being committed to producing the very best that we can. It’s using the best science and having a natural feel for the land that allows us to do it.

Smith S.M. (1996) Wine in a Warm Climate A Dissertation,
Institute of Masters of Wine 1996 (Unpublished)
Tesic. D. Hawke’s Bay Terroir Study 2000 (Unpubished)

Vine in gravels

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