Grafting in Chile

The success and positioning of certain wines or brands can have a major positive impact on a wine estate. Even at vineyard level, it can be worth changing the vine planting area or grape variety proportions.

This is true for Hacienda Araucano: the success of our Clos de Lolol red wine prompted us to explore other alternatives for increasing our production area for Cabernet Franc, Cabernet Sauvignon, Carménère and Syrah. And so, this year, we began grafting Cabernet Franc onto Sauvignon Blanc.

Grafting is a common technique that has been widely used in winegrowing since the phylloxera crisis in the late 19^th century. At the time, the use of rootstock from American Vitis species saved European winegrowing from extinction.

A rootstock is a specific vine root to which is grafted a wine cultivar whose fruit offers the desired characteristics. Once these two elements have been grafted together, a part called the scion begins to grow; the rootstock provides the root system.

For the graft to succeed, the vascular cambiums responsible for cell division in each element of the graft must come into contact with each other, to enable a connection to develop between their respective water and nutrient supply systems. So, you have decided to carry out a graft? There are a few elements to consider. What plant material will you be grafting? You can choose from young shoots, pieces of bark, chips or buds. When is the best time to perform the graft? You can choose between dormant buds (dormant season) or non-dormant buds (early spring).

Grafting does not have a direct impact on the colour or aroma characteristics of the grapes produced from the scion’s variety, because the molecules responsible for these traits are produced within the grape itself and are therefore determined by the scion’s genotype. However, there is potential for an indirect impact on the fruit’s composition, and in particular its acidity, given the rootstock’s possible impact on the scion’s vigour, the canopy configuration, crop formation, and even nutrient consumption (Keller et al., 2001a; Ruhl et al., 1988; Schumann, 1974).

Chile is a veritable paradise for winegrowing and grape production, one of the only areas in the world not to have been hit by phylloxera. This unique characteristic enables us to plant vines in our vineyards without using rootstock (ungrafted vines). And so the question arises: why graft plants rather than replanting them? Especially given that there is no risk of a phylloxera attack…

The answer is in two parts: when replanting vines, you have to consider the cost of ripping up the old ones, preparing the soil and planting new vine stock. However, if you choose to graft, you avoid these costs and save time, because the root system has already developed. You simply need to obtain the material to graft to your stump (scions, chips, buds).

Grafting also has another advantage, this time in terms of the time until the first harvest. If you replant, you have to wait for the entire plant system to develop, based on your monitoring system. If you graft, the root system is already fully developed, and you just have to wait for the plants to form before you can start production. You do not have to wait as long to begin harvesting.

And yes, it is important to note that the root system is made up of three different root types: the framework roots (which are constant after three years), smaller permanent roots (which spread and grow downwards) and fibrous or absorbent roots (ephemeral rootlets). They are all vital as they each play a specific role: anchoring (framework roots), reserve storage (carbohydrates and nutrients), synthesis and supply of the substances required for growth (hormones), and absorption and translocation of water and minerals. Starting with a fully developed root system right from the outset therefore offers a major advantage!