Research has shown that the direction of sap flow in a grape vine is in the direction of the red arrows. Sap from the roots of the vine, goes upwards through the core and young wood, also known as the xylem. It picks up carbohydrates as it moves through the leaves and green parts of the vine and transport it back to the routes and older parts of the vine, through the phloem (inner bark).What happens is when you ring-bark, is that the phloem is cut off with a ring-bark knife, so the sap flow downwards is much slower and therefore much more carbohydrates is available to the green parts of the vine.
Before ring-barking can take place, you will have to remove the bark from the stem of the grape vine, exposing the inner-bark or phloem (no. 2 in picture). Take a knife and cut through the phloem around the whole ambit of the vine, until you reach the place where you started. The cut should only be deep enough to penetrate the cambium (1-2 mm) – you will see some sap-flow coming from the wound – DO NOT CUT TO DEEP!
Now you probably ask: “Why on earth do you ring-bark?”
Well my grape growing friend, this one of the methods I use to enlarge berry size on varieties like Thompson, Crimson and La Rochelle. The reason you get larger berries lies in the slower or much less carbohydrate flow downwards – does is make sense? More is available to grape clusters!
Have a look at the berry size of this La Rochelle bunch – that’s an average of 28-30 mm (XXL!!)
Picture taken with my cellphone, so the quality isn’t that good – sorry!
When to ring-bark and when not and some important things to remember:
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Never ring-bark a young vine – the diameter of the vine should be at least 30 mm
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Always ring-bark a day or two AFTER you watered the vine – this will ensure that the vine can handle the “shock” of ring-barking
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Never ring-bark a grape vine that struggles to grow – remember you are actually hurting the vine
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In the picture where the numbers are, 1 was last years’ ring-bark and no 2 this year’s ring-bark. Always ring-bark BELOW the previous year’s ring-bark.
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Don’t cut to deep – PLEASE
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Ring-barking shortens the life of a grape vine, so if you aren’t a commercial grape grower, don’t ring-bark (although trying it for one year won’t kill your vine IF it is done correctly)
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Ring-bark at +- 10mm berry size, just after fruit-set has finished – don’t ring-bark to early, as this will have no effect on the berry size.
You might be wondering what happens to the ring-bark wound you made on the stem of the vine. Yes, it is a wound, but the grape vine has a unique way of healing itself and it is called callusing. Callusing is when the grape vine replace damaged membranes with new ones and if you have a close look at the picture of the ring-bark I made last year, you will notice the callosity that formed on last year’s ring-bark.
OK dear grape growers, know you have some kind of idea what ring-barking is all about. Just remember that this procedure should be done with extreme caution and it is NOT for the novice grape grower.
Take care and I will talk to you soon!
Danie
The Grape Guy
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