When pruning spurs with two canes, one should choose the second cane for the vegetation point and cut the first cane with respect to the crown buds normally. But sometimes the tertiary permanent structure is growing too fast an then we choose the first spur for the elongation.
That’s only allowed when the distance between the two shoots is more than 2 cm, according to the lessons in de first course and it’s again mentioned in the advanced course.
I was wondering where this figures of 2 cm comes from and is it really that important? If you look at the picture below, you can see that the dehydrations stops at the diaphragm and this prevent further necrotic penetration. The diaphragm is depositing polyphenols and other substances around the wound, and/or producing a callus able to seal the injury.
You can find more information about this here, https://doi.org/10.20870/IVES-TR.2021.4817
So I think, even when there is a short distance between the two shoots, both options will work quit well and there will be no obstruction of the sap flow. If there is a good reason for choosing the first cane, for instance to change the direction of the tertiary structure, I think that a small peace of wood above the cane should work well to make an nice sharp small cut and therefore keeping the first cane as a new spur.
1 – “Controlled Branching” is the principle, so you should grow each year the tertiary structures using a small piece of living wood. If you cut 1 buds spurs (1 bud+bourillon) you should use the cane developed from the bud (so the father cane). In this way you always grow the structure. If you have a long internode between the first and the second cane developed on the spur you should use the first in order to control the growth. 2 cm it’s purely indicative but still it is a notable growth for 1 year!
This situation (with long internodes) it’s quite frequent if you cut 2 buds spurs.
2- If you need to invert the growth direction in a tertiary structure of course you can. But in this case if you have a short internode between the canes you should follow the rules in the 4th principle “spare wood”. You are cutting a 2 years-old wood in the old spur and the spare wood must be long at least 2 times the diameter of the cut. So if you have a short internode you cant’ create a sufficient-lenght spare wood. In case of very close nodes (for example in 1 bud-spur) the diagphram can be damaged (if not by your blade, it can be damaged by the water and frost). So in this case -if you want to choose the first cane (basal cane) for the new spur you should cut the second cane (apical cane) removing the basal buds. So you can have a longer spare wood and, if you remove the basal buds, no shoots growing from that point. The spare wood will dry and you can reduce it next season. Be sure that you will assure the structure growth the year after this action, especially if you cut 1-bud spurs, otherwise you will create a small crown head in that point.
Thanks for your reply. I fully understand what you are saying. There are more roads which lead to Rome, as long as we follow the rules of S&S 😉
In the scientific article I mentioned, they did investigate prune cuttings and they find no correlation between cane diameter/distance to bud and desiccation length. But they only did experiments on one year old wood. I agree we should keep a sufficient piece of two year old wood too make a nice cut and not to damage the diaphragm. If you pre-prune in winter and do the fine tuning late February, there is no risk of frost damage. And I think a rule of thumb of approximately 2 cm is ok, depends on the situation.
Nevertheless, is great that we have the opportunity to post some discussions here ! Thanks.
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