Hello Nico! Quick question for ya… How big should the plant be before you pinch off the top? I guess, how many sets of true leaves should be on the plant before you pinch? Also, when transplanting, can I pinch off the bottom few leaves and put them deeper in the soil like with tomatoes to encourage more root development? Thanks & awesome column! Jess – via NicosNuggets@hightimes.com
Greetings, Jess ,and thank you very much for reading our site and taking the time to write us a question!
I like this particular question because I think it centers on an often-overlooked aspect of cannabis cultivation that is really quite important for healthy gardens. Pruning plants – and pinching off tops – not only helps plants to grow stronger and develop faster, but these techniques can also help generate more plant energy for increases in yield and potency.
My recommendation is not to think about your plant in terms of height, leaf sets or even age when you contemplate pinching off the top (terminal shoot), but rather its stability. I have pinched off tops of both seedlings and clones at very young, tender ages – but only once I knew they were well-rooted and planted in their permanent home (i.e., the container I intended to bring them to harvest in).
When we pinch off the top terminal shoot of a plant, the plant reacts to the injury by releasing more growth hormones. This generally leads to two (sometimes more) off-shoots developing at the internode directly under the point of departure. This is a strenuous and sometimes stressful activity for a plant – to recover from injury. If the plant is too young, undeveloped, or unstable in anyway, this can do more harm than good. The best way to ensure you do not further stress out a young plant is to make sure it is situated in its final home and has good root structure.
As for transplanting and covering lower shoots in the process, there should not be a need to do this unless the previously existing root ball got lobbed off for some reason. Instead, it is better to simply prune off the lower shoots a few days after transplanting, once the plant has settled in, spread new root growth and gained stability. Once a transplanted plant is stable, it is an excellent idea to slowly prune off lower branches in order to send more energy to the top half of the plant for flower development. Cutting off lower shoots will not have the same effect of creating more offshoots as it does when terminal shoots are removed. Just take care not to remove too many lower leaves or shoots each day, rather try and spread your pruning out over a several days so as not to shock or stress the plant.
However, in the event a tragedy struck and your root structure was removed during transplanting, then you could (in theory) trim your main stalk up to the first set of branches, trim those back, and then cover the main stem and branches with rooting hormone and plant. But this would depend on how much stem was between the bottom and the first set of branches as well as how big the plant is. It could work for a young plant, but an older, well-developed plant will likely not survive losing its root ball during transplant.
Thanks for reading everyone and remember: Grow… And help the world grow, too!