Viticultural Management
Canopy Management
In the late 1970s Dr Richard Smart was developing theories about the role of the canopy on the colour and quality of red grapes. Those theories, Prue believed, could well be applied to the Henschke vineyards. While they were already producing high quality red wines, she believed they could do better. Initially they looked at establishing better trellis systems, which in turn led to experimenting with a cooler climate and the subsequent purchase of the property at Lenswood. There, Prue believed, less stressful photosynthesis during summer would allow flavour compounds to develop. This turned out to be right, and Henschke started winning awards and media recognition immediately.
Soil Management
A number of key issues must be considered in relation to soil management, such as soil structure, moisture holding capacity, and nutrient availability. There is also a need to consider such things as how to maintain good soil porosity, the bacterial activity in the soil that leads to fertility, and the effects of pH. The water holding capacity of a soil is important in dry-grown vineyards and is improved by increased organic matter and mulching. Thirty-six percent of Henschke vineyards are dry grown and the soil management techniques now used lead to the production of very high quality fruit.
Many different techniques of soil management exist. Henschke has moved completely away from mechanical disturbance and now uses permanent sward. Mulching with wheat straw to avoid herbicide treatment under the vine is used in most of the vineyards, and allows more organic matter to be incorporated into the soil and preserves soil moisture. Earthworms also open up the soil and introduce nutrients and soil ameliorants such as lime. Mulching helps to maintain the fertility of the soil without the addition of nitrogen fertilisers, which often favour the development of disease, especially botryus. A good balance of nutrients in the top 60 to 70 centimetres of soil is important for the production of premium grapes. The vineyards are currently run incorporating organic and biodynamic practices, including biodynamic compost being produced from all the winery by-products, such as grape marc, stalks and waste water, cow pit peat and 500 and 501 preparations.
The Effect of Old Vines
Australia's oldest vineyards, dating back to the 1860s, carry an aura of wonder about them and the gnarled and free-form shapes are rarely seen in other plant species of such age. For overseas industry personnel visiting these vineyards, it is a viticultural mecca.
Soon after the establishment of the Australian vineyards, phylloxera was introduced to France where it slowly exterminated most of the vineyards and beyond into Germany and Italy. Rootlings brought into Australia from the French nursery Richter led to a similar plight in the Victorian vineyards. But sand is phylloxera's enemy as it does not allow the formation of soil cracks or damp 'super-highways' between the root systems that these sap-sucking insects love. This is why vineyards such as Chateau Tahbilk's small 1860 shiraz vineyard can still exist and why, for slightly different reasons, the Vieilles Vignes of Bollinger survived the much later devastation by phylloxera in the Ay and Bouzy regions of Champagne.
Hugh Johnson makes a tiny but fascinating reference to the pre-phylloxera vines, the "Survivors of the Plague" in his latest book, The Story of Wine. He mentions that wines made from these vines "have a certain quality and depth of flavour that sets them apart…the view of Bollinger's president is that champagne from ungrafted vines (which produce small quantities of highly concentrated juice) is too 'fat' for modern tastes!" Undoubtedly this 'fatness' is the part of the texture - the extract or intensity of flavour on the palate - that we identify in the Australian red wines from the century-old vines.
South Australia has had very different infestations affecting the survival of its old vineyards.
Firstly, the fungal disease, eutypa, which is spread through large pruning wounds, causes dieback in the arms of older vines and the vine slowly rots away and becomes unproductive.
The second limiting factor is related to economic pressures forcing growers to rip out ageing vines. These low-yielding vineyards are being replaced with a more efficient trellis design particularly suited to mechanisation and better irrigation systems. The quality rating of these new vineyards depends on the vine balance, which is something many old vineyards have realised over the years. They adjust to the nature of the not-so-benevolent rainfall during the growing season and to the natural nutrient status of the soils.
The third factor is one we hope well not have to witness again - the mid 1980s vine-pull scheme - where growers were paid to rip out their vines. This mostly involved those ancient red vineyards that had developed a harmonious relationship with nature, but not with a winery purchase price.
One feature links these old centenarians - low vigour. It is a very important feature brought on by a multiplicity of factors:
- shallow soil depth
- low level of soil nutrients
- trellis style
- cultural techniques, possibly with inadvertent root pruning
- low summer rainfall (non-irrigated)
As a consequence of low vigour comes low bud numbers and open canopies, low yields and often smaller berry size. With the lower yields comes earlier ripening and full maturity - particularly important in cooler years - and a development of extract or intensity of flavour on the palate.
Their root systems are formed in the first 10 years and from then on, the roots die and re-grow using the starch reserves built up in early winter for new growth in spring. It can almost be guaranteed that within a 10-year period extremes of drought and floods will be experienced, and the root systems will develop accordingly. The wood development appears to reach a maximum butt circumference at around 30 to 40 years. After this the live wood dies off and the butts of the oldest vines have very little live tissue. Of a 20-centimetre diameter butt, about a quarter will still be alive. Practices such as machine harvesting which requires flexibility in the vine trunk are out of contention.
The cultural techniques are similar between these vineyards. They are trained either as bush vines or on a low single- or two-wire trellis and left to survive as best they can through dry summers with minimal weed and irrigation management.
Investigation into the difference between wines from young vines and wines from old vines allow one to appraise the differences in complexity and texture. Complexity is derived from the various combinations of primary fruit flavours - developed fruit flavours and flavours contributed through the winemaking and barrel-ageing. One should look at the wines analytically to distinguish the components of complexity. Flavour descriptors are useful in looking at the fruit characters, which are split into primary fruit characters and developed fruit characters.