In the Margaret River Vineyards Summer 2010

Quality and quantity…These are key words that could be used to describe the future 2010 vintage in Margaret River. Near perfect weather has provided optimum vine growing conditions and most of the varieties have entered the veraison period and ripening fruit is showing flavour intensity at this early stage of development

The veraison period is characterized by the change of hard green berries into soft sweet berries that in red varieties see change in colour and in white varieties sees opacity and a change in colour to golden colours.

One of the many challenges that viticulturists are encouraged to perform is predicting the tonnage of fruit and providing this information to the winemaker. Predicting tonnage can be done relatively easily and a few “old hands” can just look into the vines and provide a visual estimate with some accuracy; well, most of the time (I like this method and will admit to not always getting it right!). There is some science that can be applied and growers will go to great lengths counting bunches per vine, counting berries per bunch, weighing berries and then applying a correction factor to enable a more scientific prediction on what fruit will come from a hectare of vines. The science used for forecasting a crop yield relies on the fact that berries have a lag phase of development just prior to veraison. Simply, the berry stops growing and remains relatively constant in weight. The lag phase in berry development can last between 7 to 40 days. The length of the lag phase determines whether a variety will be early or late maturing. Although this sounds complex, we know that if we sample and weigh bunches just prior to veraison and then apply a standard for accumulation of sugar (add 20%) and then allow a reduction for bunch stalks (subtract 5%) and harvester losses (subtract 5%) we can come up with a number that may represent the final yield delivered to the winery at harvest. OK, OK! enough on yield forecasting, I hear you say!! What is important is that in 2010 we reckon on having a normal to slightly higher yield at vintage and that’s what we are planning for. It goes without saying (but I will anyway), that the weather and other influencing factors up until harvest will change yields.

The fruit quality prospect this year looks very good. The more understanding about quality factors as a result of plant responses to environmental conditions the more we understand that “mild stress” on the vines, at certain times through the growing season, can vastly improve the potential for outstanding wine quality production. 
As a primary indication of fruit quality in red varieties, we know that vines that cease growing new foliage approximately 20 days before veraison will start a process of change that encourages greater colour, flavour and aroma production in the berry. This is a normal plant response to “mild stress” conditions that gives the greatest opportunity to encourage seed distribution, a natural evolutionary plant response for species protection. Fruit that has ripe seeds and no green fruit flavours (green flavours are a natural animal and insect deterrent) adds to the potential for seed distribution. Of course we circumvent seed distribution by excluding birds and other pests and we take the fruit for our own consumption. Somewhere in all this “mild stress” of vines results in smaller berry size, itself being a precursor to improved flavour and colour intensity of fruit.  Most of the colour is found in the skins and flavour compounds are found just under the skin; small berries have more skin and less pulp in a ratio that increases colour intensity and flavour. With all these factors coming forward we can already see that the potential for quality fruit production out of Margaret River this year is real and we live in expectation of an abundant yield of technically ripe fruit.

As we travel around Margaret River we can see growers are applying their bird nets in anticipation of the hungry silvereye birds that can ravage berries and cause havoc to ripening fruit. Fortunately we can also see the native Marri trees (E. Calophylla) have started to flower and this will provide some relief from bird damage to fruit into early vintage. The nectar from Marri blossom is a much preferred food source for the silvereye, while there is blossom the pressure on vineyard people to deploy nets is reduced. An interesting fact is that silvereyes that only have grapes as a food find it difficult to survive as they can’t replace the energy used in seeking out and eating grapes and will loose condition. Grapes are way down the list as a food preference for silvereyes and they are desperately hungry when feeding on grapes. Simply, the biologic “engineering” of the silvereye only allows the beak to penetrate the skin of the grape and then by extracting the beak and then licking the silvereye consumes a small amount of sweet liquid, the sum of which generally doesn’t equal the amount of energy expended in flying and other activities. The major issue with silvereyes is that the damage done by piercing the berry results in secondary infection by moulds and bacteria that spoils the grapes for winemaking. The best protection is placing netting over the vines and this has become an annual event in early February, the result is less angst and a better night’s sleep for growers and viticulturists once the nets are on.

A good night’s sleep is all important in the lead up into the vintage period. Unusual hours of work can be expected and everyone pitches in to get the crop off in the short window of opportunity for desired fruit flavours. This year the estimated start date of vintage in northern Margaret River will be around the 15th February. The harvesters are being cleaned and serviced in anticipation of harvest and there is excitement building in the region as sampling berries reveals the prospect of producing great wines.   

Contributed by Bruce Pearce

About Margaret River Discovery Tours
Sean Blocksidge is the owner operator of the Margaret River Discovery Company, an avid photographer, blogger and South West WA ambassador. In 2010 he won Western Australian Guide of the Year and his tours have been rated the #1 thing to do in Australia on the Tripadvisor website for the past two years.