Deconstructing the Masseto vineyard: Scion and rootstock

Masseto is one of the the world's leading Merlot wines and its 6.63 ha vineyard is ensconced within the confines of the larger Ornellaia vineyard in Bolgheri, Tuscany. It has been difficult to obtain information on the details of this vineyard so I have undertaken the task of deconstructing it using data from publicly available sources as well as reasoned assumptions. I began with the soils and now turn to the cultivar and rootstock.

Scion

The cultivar selected for planting at Masseto was Merlot. According to masseto.com:

Among the first people to realize the potential of the great terroir of Massto hill (sic) was the great Russian-American enologist Andrè Thcelicheff (sic), a man of great experience who contributed to the conception of Masseto in the early 1980s... He loved Merlot and immediately felt that Masseto Hill would, thanks to its characteristic terroir and unusual climate conditions, be a dream place for Merlot to express its beauty. Following his precious advise (sic) the team at Masseto planted the vineyard and committed themselves to make, over the years, the dream come true.

Other considerations which make this cultivar especially suited to the terroir are as follows: 

1. It performs well in similar clay soils on the Right Bank of Bordeaux
2. It provides the estate with the flexibility to produce both a mono-varietal and a Bordeaux-style blend in combination with varieties from other parts of the larger vineyard.
3. Merlot does well on well-drained soils with good water-holding capacity. The subject vineyard is comprised of loose clays and pebbly sands at the top of the slope and less-clayey soils at the base. The mineral structure of the clays allows the absorption and storage of at least their weight in water.
4. The climate is amenable to the growth and ripening of this variety
1. Average annual temperature of 14℃ and 18.6℃ from April to September
1. Early bud break of Merlot not a risk factor in this environment
2. The cool winds which come from the sea and the moderate temperature in August and September allow for slow, regular maturation of the grape components
3. The microclimate provides both direct sunlight and reflected sunlight from the sea to the west 
4. Average annual rainfall of 600 mm/yr.

The characteristics of the Merlot grape are (extension.org, Growing Merlot Wine Grapes):

• Medium to high vigor with excess vigor quickly creating “a dense canopy due to lateral shoot development”
• Does well on deep, sandy loams or well-drained soils with good moisture-holding capacity
• No known incompatibilities so rootstock solution can be made based on site/soil conditions and cultural practices
• High vigor rootstocks should be avoided
• Any rootstock will reduce the tendency for high nitrogen levels in the vine.

Rootstock

I do not have information on the rootstock in use at Masseto so this is one of those cases where reasoned assumptions will be applied. The first step in my rootstock-selection methodology was to develop a list of candidates and their characteristics. This list was developed from the following sources:

• Rootstock Selection (http://iv.ucdavis.edu/files/24347.pdf)
• Yalumbanursery.com
• wine-grape-growing.com

Once this list was developed it was culled based on two of the most important criteria (as I understand it) -- Phylloxera and nematode resistance.

The next step was a further culling of the list based on the rootstock’s influence on the scion. If it was a medium-/high-vigor roostock it was eliminated because both the clay soils and the Merlot cultivar have high vigor and I am looking for a rootstock that would be mitigating (see extension.org).

The remaining rootstocks were then culled based on the soil adaptation. Rootstocks that were amenable to moist clay soils were retained. The remaining rootstocks/clones at this time were:

• Berlandieri x Riperia
• 5BB
• 5C

• Riparia x Rupestris
• 101-14 Mgt
• Schwarzmann

I next turned to soil adaptation and while the others were suited to moist clay soils, the Schwarzmann was adapted to moist deep soils, a situation that does not hold at the subject vineyard.

The next to go was 5BB, because, according to UCDavis, it is susceptible to root rot. The two remaining candidates then were 5C and 101-14 Mgt.

Our selection process has thus brought us down to one clone in each of the two rootstock classes and the 101-14 Mgt will be selected because of the parent characteristics (Catherine Cox, Rootstocks as a management strategy for adverse vineyard conditions, gwrdc.com.au):

• Offer low-moderate vigor to the scion (versus med-high vigor in the competing parent)
• Perform best on soils that dry out slowly and have moderate-high water holding capacities (perfect match for the Masseto vineyard soil type). The 5C parent class perform best in free-draining soils of moderate depth and fertility.
• Impart low vigor to the scion and thus are suitable for sites with high fertility

The position then, is that the Masseto vineyard supports Merlot scions on 5C rootstocks. I hope that they correct me if I am wrong.


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