These two amazing horticultural tricks – nicking & notching – were outlined by Toby Buckland in Episode 18 of the 2020 season of the BBC’s great garden show, Gardener’s World, which originally aired on 17 July 2020. (** If you’re in the UK you may be able to view again on the BBC iPlayer.)
Apical dominance relates to the fact that as plants and trees grow, they send hormones down the plant to keep lower buds and branches dormant.
Nicking and Notching are tricks to control the flow of these suppressant hormones to encourage (for notching) or discourage (nicking) branch growth off a main stem or tree trunk. A little digging around on the internet reveals that this is a key technique in developing apple trees, for example.
Notching is when you cut a small cut into the bark of a tree above a bud that you want to encourage to grow. Use a very sharp clear edged knife blade (eg – not serrated), and also ensure that you don’t cut more than a third of the way across the full stem. The cut helps block the flow of growth suppressing hormones which flow down the stem of the tree to help the top of the tree keep dominant growth.
Nicking inhibits the growth of a branch, so instead of cutting above the branch or bud, this time you make your cuts below the branch. This hinders the growth hormone that comes up from the bottom of the tree, so can help to keep lower limbs and branches from continuing to grow too large.
For further information and a review of the development and research into apical dominance see Tesfamichael H. Kebrom’s article ‘A Growing Stem Inhibits Bud Outgrowth – The Overlooked Theory of Apical Dominance,’ published in Frontiers of Plant Science, 31 October 2017. (https://doi.org/10.3389/fpls.2017.01874)