Last year I wrote on the practice of provignage at Domaine de la Bergerie. In a quick two or three sentence recap, provignage is an ancient method of propagating plants, including vines, obviously. A branch or runner is pinned under the soil (with a peg of some sort, or simply by placing a rock over it), after which it will put out new roots, and by cutting the runner/branch joining this new growth to the parent plant – hey presto! – you have a new plant. For free. It was, naturally, an excellent way for peasant vignerons to propagate new vinestock for their vineyard (there’s more detail in the post linked above if the above isn’t clear).
And then along came phylloxera. And now, if you believe the books, vines in France and other infested regions of Europe must be established on grafted phylloxera-rootstock if they are to survive. Either that, or planted on certain phylloxera-unfriendly sandy soils.
Which is why the vines at Domaine de la Bergerie were of such interest to me. They had been propagated using provignage many decades before, and seemed to be thriving, despite living on their own roots in a damp clay soils, just perfect for phylloxera. Proprietor Yves Guégniard didn’t seem to know why or how they survived, but I suspected it was something to do with the fact that in every case the original runner connecting the new plant to its parent had not been cut.
I haven’t thought much about it since until, late last year, at Château Boyd-Cantenac in Margaux, there before my eyes were yet more vines propagated in the same manner. The picture above shows the runner, about as thick as my thumb (and so nowhere near as old and crusty as Guégniard’s vines) which originates with the parent (on the right) and dives beneath the surface towards the roots of the offspring plant (on the left). Here, however, owner Lucien Guillemet referred to this practice not as provignage but as marcottage. Having read around, I can see no difference between the two practices; I had thought it might refer to whether the runner is cut or not, but it seems not. Descriptions of the two are identical; I would be delighted if any viticulturists or plant scientists out there want to chip in with an explanation of how they are different, if indeed that’s the case.
I asked Lucien what would happen if the runner were cut, and he was quite certain in his response; the offspring plant will die. This clearly indicates it is reliant on its parent for support, and so my initial suspicions were correct. Its own (no doubt phylloxera-infested) roots are not enough to maintain vitality, but with the help of its parent’s American rootstock it survives. Does any nutrition come from the infected root system at all, I wonder? Is the plant entirely dependent on its parent for life, or is it more of a crutch? And if dependent, is it really a separate vine, and not merely a branch? Should this be taken into consideration when looking at planting density, numbers of buds and bunches, and yields?