There are different clones (types of cutting) of Shiraz in the Shiraz Republic. Does the type of Shiraz clone make a difference to wine?
This is a common question to which I have an unsatisfactory answer. Clones have different characteristics to each other. Shiraz like all wine grapes is grown from cuttings. In selecting the clones used in the Shiraz Republic, I looked for variety, low yield and drought tolerance, but most of these qualities come from the rootstock (Poulsen 1104), but that is another story.
All Shiraz clones share similar characteristics, presumably because all were sourced from the same hillside sites at Hermitage in France. Shiraz arose in the south east of France around the 1300s as a chance cross between Dureza and Mondeuse Blanche. The first successful importation of Shiraz into Australia was made by James Busby in 1832, he personally collected his cuttings at Hermitage. These vines were subsequently propagated by William Macarthur and sold as cuttings to growers throughout Australia.
Clonal differences are mutations in the genetic code of the grape bearing vine, particularly where the grapevine shoots out of the main vine. These mutations occur naturally and spontaneously over time, starting with a single cell and subsequently spreading to take over the entirety of the vine. The mutation occurs in one shoot which may then grow itself into a large, hardened vine. This vine is now fairly meta-static in its clonal difference. Until perhaps it mutates again.
But clones are different thing to clonal differences. Human intervention takes that main “new” vine which has an interesting clonal difference. This “mother” vine can then be asexually propagated, via cuttings and graftings. With luck the mother vine will not mutate and can remain a source of consistent new clones. Groups of clones from a certain mother vine with the same characteristics will be given an identifying number by the powers that be. These will usually be a university or Department of Agriculture which can ensure quality control when registering clones and such. The clones then get sold to other nurseries and vineyards.
It is important to note that clones cannot mutate too much or they will lose their familial resemblance as a specific grape. The differences among clones can be minute or more substantial. And the changes cannot be sexual in nature because when that happens (via cross-pollination or hybridization between two grape varieties) science deems the result to be a new variety, not a clone.
In terms of having a direct effect on the quality of the wine, clones may offer distinct advantages over their peer competitors. The Shiraz Republic favors clones which produce small grape berries and smaller overall yields. But then if I had a dollar for every time I read about the “intensely flavored” grapes that come from a winery snootily choosing Clone X, I would be a rich man. No-one claims to have planted inferior vines!
Some clones produce a darker or lighter color, and flavour descriptors associated with specific Shiraz grape clones vary subtly, but it seems there’s a clone to suit any discriminating palate.
The dangerous trap in discussing clones is thinking that there must be a “best” clone. But there really isn’t any “best” clone because of the vast impact “terroir” makes on viticulture. What works in one place may not work in another. Differing soil composition, temperatures, average rainfalls, vineyard drainage, exposure to warm sea breezes, all the million factors that go into choosing a vineyard site negate the concept of universally superior clones.
But what does it mean to when choosing grapes to buy to make your wine? Well this is the “unsatisfactory” part of the answer. I can’t tell much difference! I keep threatening to make up a batch from each of the clones, but even after you do that, baume’, the different barrels etc, how sure can you be that it was the grapes that made the difference. Most people choose their favorite clone on the basis of sentiment. If you come from SA or worked in the Pyrenees then you may like to choose a clone from there. The truth is there are clonal aspects which played a greater role in my choice. Some clones may vary in grape cluster size and density and thus help even ripening among the grapes. Others may undergo earlier budbreak or earlier ripening. Some possess more or less acidity. Simple (lack of) vigor in a clone was a desirable attribute as the goal was for low yields; and some clones prove more resistant to some diseases.
But when it’s all said and done experimenting with different clones in different vineyard blocks and then mixing the resultant wines in varying lots and proportions can be fun the winemaker.
PT23 is an old Australian clone which is widely grown NSW selection (although I have seen it referenced as a Victorian clone). Selected in Griffith from a pruning trial in the early 1960’s. (PT = ‘Pruning Trial’.) PT23 was selected from vines which were themselves descendants of the original 1832 Busby importation. PT23 has a reputation for blackberry, black pepper, intense colour with greater tannin.
Shiraz Clone SA1654 is probably the most widely planted clone in Australia.
Cuttings from these vines were propagated in South Australia and planted in a replicated clonal evaluation on the Barossa Viticulture Research Centre (BVRC). In 1973 the three highest selections were selected for virus testing. One selection was shown to be virus infected and the other two were propagated by the Department of Agriculture for release to Industry. The name SA1654 means that was the code for the original vine that all of the subsequent cuttings were made from.
Reputed characteristics of wines made with SA1654 include an intense crimson colour, chocolate, spice and black pepper flavours and fine grained tannin structure. Others talk of chocolate, fruit cake aromas with medium bodied but complete palate.
Best’s Old Block
The third clone is known as Bests Old Block, which may be the same clone as the St Peters vineyard of Seppelt. It is reputed to have come from the fifteen rows of vines planted by Henry Best, recorded as “Hermitage” by Henry in his daily journal. I gather the clone is now referred to by the CSIRO as the Concongella clone and it is the mother clone of all subsequent Shiraz plantings at Best’s Great Western. It is reputed to have fragrant and mineral characteristics(!?).
Since 2014, we have been using this highly reviewed clone. One of 6 selections from some Tahbilk trials in the 1970’s (R6WV28= Row 6, West Vine 28). R6WV28 is the most widely planted of these Tahbilk trials and is known for its early ripening, low yield, lively palate, soft plush tannins, a touch of peppermint and cedar and deep colour.