|Two different sets of cuttings. The shanks of the top and bottom cuttings are very close to the same diameter. Both with Vidal as the top section and V. riparia as the bottom section.|
I was grafting at the nodes to take advantage of the nurse-bud phenomena and to have a viable bud as close to the graft union as possible.
Two things jump out, the V. riparia selection does not have a diaphragm at the bud.
The other thing is that the V. riparia has much, much thicker wood. I don't know if that is a factor that makes V. riparia inherently more cold hardy than Vidal but it can come into play in an unexpected way.
People managing vineyards use "formulas" to prune each vine. These formulas are developed at research Universities for each variety and growing region. For example, they might use a formula of 20 + 10 for Vidal. That means they leave twenty fruiting buds for the first pound of "prunings" and then ten additional fruiting buds for each additional pound. Sometimes that morphs into "leave a minimum of twenty buds and then leave an additional ten buds for every pound of cuttings."
The goal is to balance the vigor of the vine with the amount of fruit that we are going to ask it to ripen.
The problem is that folks out working in the vineyard don't weigh the cuttings on a scale. They estimate the weight visually. If you have been calibrated on V. riparia (unlikely) or Concord (very likely) then you will grossly over-estimate the weight of the wood you are removing from a Vidal vine because the dried pith is no heavier than shaving cream.
|Grape Rootstocks of interest for Michigan. A V. riparia selection is listed third-from-the-bottom.|