What is your take on close planting? Under what conditions would you consider it, especially in relation to Cabernet and Merlot?
Great question. We will try to answer this as best we can. Planting density sparks a great deal of debate, especially with some South Australian nursery sources, or the international high flying Michel Rolland claiming that it improves wine quality.
Where does this thinking come from?
There is no single reason for high planting density - simply planting closely does not ensure greater concentration of fruit flavours, nor does it ensure the greater root-competition induced improvement of flavours. Conversely, we are not aware of any research that shows planting widely degrades the quality of the resulting wine. It all depends on the site and the vineyard management.
High density planting comes from having narrow rows and close vine spacing.
|Vineyard in Bourgogne's Côte d'Or départment.|
In Europe there is both high density and low density planting.
The Bourgogne currently plants on a basis of 10,000 vines a hectare (1m x 1m) for Premier Cru and Grand Cru - though there are as many variations on this theme as there are vineyard owners, with some planting "out" to 1.3m x 1m. and some "in" to 1m x 90cm. These vineyards are of course planted to the variety Pinot Noir.
In the Bordeaux regional AOC's, the traditional home of Cabernet Sauvignon and Merlot planting densities range from 4,000 to 10,000 vines per hectare.
|The trellis’ in some of Bordeaux are much like that in McLaren Vale – wider spacing’s, and high cordon height – particularly around Sauveterre.|
|High density in Bordeaux with 1.2m row width.|
Sources reporting on pre-phylloxera Bordeaux vineyards had extremely dense plantings - up to 28,000 vines a hectare - but we don't know whether these densities produced better wines. The best source is considered to be the early 20th Century wine scholar George Saintsbury and he could not differentiate between pre and post phylloxera wines.
Balancing this are vineyards in Spain where they entirely consist of goblet pruned, free-standing vines - all quite old and sufficiently widely spaced that tractors can pass all four ways through the vineyard, for cultivation purposes.
Spanish low density vineyards in Rioja, like those pictured, are considered to be some of the most valuable in the world.
|Tempranillo in Rioja Alavesa.|
|McLaren Vale vineyard c.1970.|
Tio further this many of the original McLaren Vale vineyards were similarly planted as low density vineyards. Some of these are still in production and make excellent quality wine.
Climate plays a part.
Conditions in south eastern Australia and high rainfall parts of western Europe are very different. Also in the New World vineyards we have the flexibility, in most years, to irrigate - and this alone is a massive change to the root environment and to productivity compared to the 'Old World' where irrigation is limited.
European experience is not to be sneered at - but this is not directly applicable to Australian sites. It suits the cool-climate and shallow soils of say Bourgogne - but this does not necessarily apply to the deep, rich silt loams of say Langhorne Creek - or the volcanic soils around Stellenbosch in South Africa
|Close planting at 0.8 m vine spacing with unilateral training.|
Narrow row width = high density.
Spacing of the vineyard rows is more straightforward.
If each row of vines represents the machines in your "factory" then the greater number of factories you can have, the greater the production from the vineyard. Therefore the greater the number of rows, the greater the potential yield.
The vine is acting on intercepted sunlight so it is important to minimise shading of adjacent rows. Smart and Robinson (Sunlight into Wine), came up with the coefficient of canopy height plus 10% as the row width (1.1H). Just note that you can't go too close together as it makes tractor operations difficult. In practice rows narrower than 2.6 meters begin to limit tractor operations.
|A McLaren Vale vineyard with 2.4m vine row width. Note the vineyard has difficulty with routine operations like fertiliser application and weed control because the rows are too narrow for contractor machinery.|
Should you plant Cabernet and Merlot in high density?
To directly answer the question, Cabernet Sauvignon and Merlot can be successfully grown at low to high densities, they are in many cases including in Bordeaux.
Climate, and vine vigour are the factors to consider.
If you have a low vigour, dry site then close planting may not be the right way to go. We would look to planting these closely if the climate and soils resembled European conditions - which they can do in the Adelaide Hills, an in some other areas.
Whichever way you go what we would aim to achieve, in all cases, is a "balanced vine". We have a strongly-formed opinion that overly stressed vines make stressed wines - and a balanced an healthy vine will make good wines - almost regardless of other factors.
Narrowing vine rows can be a good option of increasing vine density, but tractors are going to limit how narrow you can go.