Matthew Partridge, Viticulturist & Marc Scalzo, Winemaker
Australian Viticulture, December 2010
Our Roussanne vines are located in our Shelley's Vineyard, approximately 10km east of Rutherglen, in north east Victoria. We have 0.51ha planted in total. The Roussanne was grafted over from Nebbiolo in 2004; the Nebbiolo was originally planted in 1998. The Roussanne clone planted is CX Vassal. All our Roussanne is planted on Schwarzmann due to its resistance to phylloxera and its moderate yield and vigour characteristics.
Why did we decide to grow Roussanne? After researching climatic indicators, we identified the suitability of Rutherglen for producing dry table wines from the later-ripening varieties from the warmer Mediterranean regions. This included varieties such as Viognier, Marsanne and Roussanne from France's Rhone Valley. The Roussanne is part of one of our Rhone-style blended wines; the Roussanne is specifically used to add weight and length to our premium Renaissance label which is a Viognier-Roussane-Marsanne blend.
The Shelley's Vineyard is planted on a gentle ridge which rises from 170m to around 190m above sea level. There are no large bodies of water nearby. The Roussanne is on a gentle, south-west facing slope. The surrounding land is all undulating countryside.
The topsoils are a little variable, consisting of clay lawns on the lower ground, becoming interspersed with gravel, shale and quartz deposits along the higher ground. The average depth of the topsoil is 400mm. The subsoil consists of light to medium clays with reasonable drainage characteristics.
For Rutherglen, the mean January temperature is 22.4°C and the mean July temperature is 7.2°C with an annual heat summation of 1770. The average annual rainfall is 589mm. For the 2009-10 year we received 511mm. Rain predominately falls throughout winter and spring.
Frosts occur infrequently in October and very rarely in November. Fortunately, most of the vineyard is planted on rising ground with good air drainage.
Spring is typically the windiest time of year when moderate afternoon breezes are common. During late summer and autumn there are often localised cooling breezes in the evening resulting from air drainage from surrounding hills.
Trellising and canopy management
The rows of Roussanne are planted 3m apart while the vine spacing is 2m. This equates to 1666 vines/ha. The vines are trained onto a single cordon wire at 1.2m. There is a fixed wire at 1.8m and one pair of moveable foliage wires which we use to create a VSP canopy.
Shoot thinning is carried out at around EL 12. There are a number of reasons for this, including yield regulation, reducing shoot and bunch crowding, and reducing pruning costs for the following year.
Wire lifting is carried out when the shoots get to around 60cm in length. We aim to create a single cordon Ballerina style canopy with approximately 60% of shoots vertically positioned and the remaining 40% left to grow outwards and fold down. In Rutherglen, we find it is necessary to provide some shade to reduce the late afternoon heat load on the fruit during ripening. The row orientation is northwest-southeast so some differential lifting is carried out to create more exposure to the morning sun and less exposure to the afternoon sun. Excessive fruit temperature can occur if no shade at all is present on the western side.
Bunch thinning is carried out if warranted by yield estimates as we find it difficult to achieve mid-palate fruit intensity if the crop load is much over 10t/ha.
Irrigation and soil management
The Roussanne is all drip irrigated. The drippers are spaced 0.6m apart with an application rate of 1.6L/hr, or 0.89mm/ha/hr.
The vineyard is irrigated from a dam. The dam is supplemented by pumping from the River Murray and also a groundwater bore. In wetter winters, such as the one we had this year, we also capture some run-off water.
A typical irrigation volume per year on this variety in this vineyard is 2.6ML/ha. We normally start irrigating in early November. During January and February, the irrigation program normally consists of two mid-week applications of around four to five hours and a weekend application of around eight hours. Irrigation scheduling is based primarily on the appearance of the vine. This is backed up with gypsum block readings and also evaporation figures. After veraison, we typically work on replacing around 25-30% of evaporation. In whites, we don't practise RDI as we are trying to ensure a larger berry size with clean and fresh flavours.
In the past, the vineyard floor was sown to a sward of perennial Victorian ryegrass. Since this time, we have been letting the native grasses come through. The sward's main function is to soak up excess moisture and improve trafficability in springs like the one we've had this year. We keep it slashed through September and October and then allow it to grow a bit longer through November and December. During this period, the cover crop also provides habitat/shelter for predatory insects. We don't apply mulch to the Roussanne.
Undervine weed control consists of a winter application of Roundup and Hammer. Stomp and Simazine are applied pre-budburst. This normally gives very good weed control through to January when Sprayseed is applied, and we then follow up with another Sprayseed application after harvest.
Pest and disease management
The Roussanne doesn't suffer any particular pest or disease problems. We put a botrytis spray out at flowering and also prior to bunch closure. Powdery mildew is controlled with a preventative program of sulfur, DIVIls and Cabrio. Downy mildew is controlled with a preventative program of either copper or Captan.
We hand spur prune the Roussanne after mechanical pre-pruning. The variety seems to be relatively fruitful from basal buds and it is significantly cheaper than cane pruning. We also find the quality to be very good from this style of pruning.
We typically prune to 28 buds per vine, or 14 buds per metre of cordon. The exact level of pruning for each season is determined mathematically by relating the previous yield to our target yield (10t/ha) and adjusting bud numbers accordingly. The vines have settled into a relatively consistent cropping pattern now and so this bud number tends to give us close to our target yield without bunch thinning
Future methods of management
In terms of wire lifting, we are keen to get less exposure onto the fruit early after fruitset, particularly on the western side of the row. The aim of this is to increase the acid retained at harvest. We will be mindful of avoiding over-exposure and excessive fruit temperature on the western side.
We look to pick when we have moved out of any green flavours but while the flavours are still minerally and the acid tight. We don't want the grapes to lose all their natural acidity and the flavours to be into the melon strectrum.
A typical analysis of our Roussanne at harvest:
Sugar (baume) 12
Acidity (TA) 5.50
Over the past three seasons, the Roussanne has yielded an average of 9.10a, with a high of 11.2t/ha.
Average phenological timing:
Fruitset late November
We use our Roussanne in our premium Renaissance Viognier-Roussanne-Marsanne blend, which retails for $30. The variety is used to add the backbone to the blend. The wine is barrel fermented and some solids are used in the ferment to add texture to the palate. Our Roussanne has great spice with pears and a hint of floral notes. The Roussanne adds structure and weight to the mid and back palate.
Biggest challenge in producing quality Roussanne
We have found that to produce really high quality Roussanne we need to ensure that we have a canopy that is big enough to protect the fruit and minimise burning and over exposure to the sun. We have also found that a slightly large berry size gives much fresher and fruit-driven characters to the wines that are produced.
Advice to other growers
As with all vaneties, do your homework on site and clonal selection. Roussanne is not very vigorous if left unchecked.
Our vines are grown with the aim of producing fresh and clean fruit, with the hope that at harvest the vines have a medium sized, fresh canopy that allows only dappled sunlight through. So, be willing to water and provide a larger and fresher canopy that will provide protection from the sun.
The correct timing of shoot and bunch thinning is critical to fruit quality.
We have also found that Roussanne will have two to three seeds per berry and that those seeds are very large compared with the actual berry size. This has an unexpected result if you receive a summer storm close to harvest as the seeds will 'pop' out through the side of the berries, splitting them and allowing a large wound and site for rapid infection with berry diseases. To minimise this effect, we have found that watering the vines prior to any summer storms means the berries are turgid and will not rapidly draw in any moisture and, as such, 'pop' the seeds out.