Take time to choose the right cultivar and rootstock – Vineyard
With more growers looking to plant vines for the first time, Hutchinsons agronomists William Robinson and Tim Ferris offer some advice about rootstock and cultivar selection ...
Good site selection is the single most important consideration for any successful vineyard, and the characteristics of that site, particularly soil type, solar intensity, and growing degree days, greatly influence rootstock and cultivar choice.
All too often, the decision has been made to plant vines on a piece of land, rather than thinking whether they should be planted there.
Soil type and pH are the two main factors that determine rootstock selection, so get soils tested before making any decisions.
Vigour is key, and on particularly sandy or less fertile soils, growers may opt for a rootstock that conveys slightly more vigour, such as SO4 or Fercal, whereas on a perfect sandy clay loam, a less vigorous rootstock would be more suitable, such as 3309-C.
If pH is very high, the rootstock needs to cope with such extremes, to ensure vines can access nutrients from the soil-high pH restricts uptake of nutrients such as iron. Fercal is the main option for high pH soils.
Getting rootstock choice wrong could result in an overly vigorous vine that is difficult to manage, at greater disease risk, or is less fruitful as vegetative growth is out of balance with reproductive growth (i.e. grapes).
Where there is significant soil variability across a site – as may be indicated by TerraMap high-definition soil scanning – it is possible to plant more than one rootstock with the same variety grafted above, and therefore avoid spending unnecessary time trying to manage weaker vines over the next 40 years.
For example, S04 + Pinot Noir may be planned on most of the site, but if there is a chalky vein running through the land, Fercal + Pinot Noir could be planted on just the chalky area.
Doing so requires careful planning, but it is possible with technology such as TerraMap and the Omnia platform to map and analyse variability.
When planning rootstock, check lead times with your supplier. For common material, such as S04, 3309-C and Fercal, a year is generally the norm, but longer may be required for less mainstream rootstock and variety combinations.
When selecting cultivars, the key is to understand the site and the end goal in terms of the wine you want to produce (acidity, sweetness, flavour profile, colour, etc), then work backwards. Planting the wrong variety in the wrong place makes it hard, if not impossible, to deliver what’s required.
Site characteristics, notably growing degree days, solar radiation intensity, drainage and spring frost risk, have a huge bearing on the ability to meet quality criteria, so look at such data in detail when evaluating cultivar options.
The temptation may be to go with Champagne classics, but temperatures could mean the focus should be on an earlier-maturing variety like Solaris, Ortega, Madeleine Angevine, or the like.
If the aim is to produce a still Riesling or Sauvignon Blanc, for example, acidity needs to drop to a lower level and sugars need to be at a higher level than for a sparkling wine. This can only happen with sufficient sunlight intensity on the grapes to break down malic acid, which will also require careful canopy management to achieve.
Equally, for some cultivars, GDD carries slightly more importance than solar intensity. Varieties like Bacchus and in some respect, Pinot Noir and Chardonnay, generally need a little less solar intensity, but do need the temperatures to ripen.
Ideally, look at historic data over multiple years to build an accurate picture of the conditions at any proposed site, considering both average data and seasonal anomalies. Some growers may prefer to “hedge their bets” by planting both sparkling and still varieties.
In all cases, the aim should be to establish more than one clone in different areas to balance the tendency of some vines to go a little bi-annual, cropping heavily one year, then light the next.
For something like Pinot Noir, many different clones are available, ranging from Burgundian to Champagne clones, so take time to find what’s right for your site. That may be something that flowers slightly later, matures earlier, or has slightly longer, more open bunches.
Finally, for growers going down the organic or biodynamic route, there are additional considerations, particularly around disease risk.
Look for varieties with strong disease resistance, but also consider the additional time and labour demands for canopy management and bunch thinning – the two main tools for managing disease.
Site characteristics are important here too, as damp, sheltered sites, may be at greater risk of fungal diseases, such as mildew.
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