I haven't employed that method, but physically it will work. By damaging the cambium layer, the circulatory system of the plant, you're interrupting the sap flow and re directing it in to that bud instead of up that cane. That is essentially what you are doing when you prune, also. It is essentially what you are doing when you cut the top of a stock off above the inserted bud to push it into growth when you create a budded plant. The down sides I can imagine are 1. by damaging the cambium at that point, you may easily destroy the ability of sap to flow up past that bud, causing the tissue above that bud to die from lack of nutrients and sap. And, 2. potentially creating a wound to give entry to pests and diseases including possibly the bacterium causing crown gall. Otherwise, definitely, the method, if done properly, will cause a dormant bud to eventually break into growth because of redirected, increased sap pressure.

malcolm_manners

2 years ago

Yes it works well. You could probably increase your success rate by making your notch a bit wider. We use it on bud-grafted roses to force the scion bud to grow.

Here is how/why it works: In a normal, uninjured stem, the top (growing shoots, younger leaves) is constantly sending auxin (a hormone, indole-3-acetic acid) DOWN, toward the roots. Auxin stimulates strong root growth. But as it passes behind those dormant side buds, it also gives them the message "don't grow yet." At the same time, the roots are sending cytokinin (another hormone, mostly zeatin, but also perhaps some dihydrozeatin) UP, toward the shoot tips. That hormone says to dormant buds "grow now!" So in the uninjured stem, those side buds are being told to grow, and not to grow, at the same time. Mostly of them will stay dormant, but once in a while, one of them grows, when the balance is right. By notching above a bud, you stop the auxin (the "don't grow" signal), so that the only message arriving to the bud is the "grow now" message of the cytokinin. This is also why, as soon as you prune a cane, the top bud or two immediately start to grow -- you've removed the source of auxin from above. In this case, you are tricking the side bud into "thinking" it is the top bud, by cutting off the auxin flow.

https://www.gardenweb.com/discussions/5778863/notching-above-a-bud-has-anyone-tried-this#n=43

That should explain what it’s all about.

Thank you, but credit to Hal David.

Very useful info! We haven't been really pruning, just letting things grow as they want since our plants are young and needed to put on size. However this year some of them are leggy and/or sparse so doing some shaping through pruning or notches is probably prudent.