When and How to Prune Marijuana Plants
When and how to prune marijuana plants: depending on why you want to prune your plants, you’ll need to do it one way or another, or at a certain time or another. You wouldn’t prune the same way if you want to make a parent plant, then if you wanted your plant to have a more distributed production in order to have a more discreet plant or if it’s just the way that that particular variety is grown.
We’re going to talk about a few different pruning situations, along with a picture and an explanation so that you know where you have to cut depending on the result you want, because not all pruning is done the same or for the same reason, so each type has a different effect on your plants.
Where to cut if you want to get a clone:
To do this, you need to make sure that the part of the plant that you want to use as a cutting is above where you’re cutting, and that there are a few small branches on it. You also need to leave a knot above the spot where you cut so that when you plant it again you can plant it deep up to the knot, because that’s where the roots will be coming out of. You’ll need to cut it just like the picture, take off the little branch from the knot where we’ll be burying our plant, make sure that you cut it at a 45º angle, and then you should put it straight into some rock wool, jiffy, or whatever you prefer. After a few days, following the right steps (go check out the article we’ve done specifically on rooting clones), your plant should have some roots.
Where to cut with the FIM pruning method:
The FIM prune is a type of cut that’s not followed through on, and it produces 4 or 5 new sprouds. At the beginning they may seem strange and deformed, but they’ll soon turn into sturdy branches, you just need to give them time. This kind of technique is perfect if you want to turn a cutting from another plant into a parent plant. Using the FIM method, you can get a lot of new branches on your plant, which will cause new slip sprouts to appear on the upper layers, which is what you’re after. The first time I tried this I got very good results even though I had never done it before, even though it might seem difficult, you just need to try and leave the middle tip when the cutting is still small, like in the picture, taking away about 60% of the tip and leaving the little leaves that were starting to come out. If you want, you can repeat the process when the tip begins to come out again. You’ll end up having an extremely dense parent plant, which’ll be extremely productive, meaning you can have a SCROG set up with a mesh in your grow room or grow tent.
Where to cut to grow two central calyxes:
To get two central calyxes and have a more centered harvest, all you need to do is cut above the two branches that we want to let grow. The cut must happen after a point in which two new branches are appearing, leaving about 1cm of trunk after those two branches. In the picture we can see the two sprouts coming out of the trunk, and even a little extra bit. In a couple of days the wound will close and the two new central points will have your plants entire attention. That’s where the most bud will be concentrated because your plant will see the two new branches as the central eye of the plant.
Where to cut if you want a nice small, wide indoor plant:
To use this prune technique you’ll have to be a bit more careful, because you’ll have to cut along the fattest part of the trunk, and your plant will have an open wound that you’ll need to cover up. This way you’ll manage to get the plant to have a high density of flowers on the inner and outer branches, creating a blanket of buds of around 40x40cm with which you can fill a square meter grow tent with just four plants or a 1,2×1,2 grow tent with up to 9 plants. This kind of pruning helps spread out the production in the shape of smaller buds but in larger quantities. You’ll need to make the cut right around the height of the lower branches, leaving the plant looking kind of like a candelabrum, allowing the shorter branches to end up at the same height as the longer ones. You’ll need to use a scarring paste on the wound or even wax from a candle so that no dirt or insects can get in and put your plant’s life in danger.
Pruning lower branches to concentrate production at the top (Lollipop):
Some strains absolutely hate it when you prune them to increase their number of branches, so in these strains what you’ll want to do is increase the amount of production on the central stem. These strains tend to be indicas. The one that’s easiest to recognize with this kind of shape is Critical+. These plants center most of their production on the main “eye” of the plant, the central calyx, so to get the most out of these plants you’ll need to place a whole lot together and prune/trim the lower branches. This way you’ll be able to grow up to 16 plants per square meter without them getting tangled. The idea is to prune those branches that come out over the flowerpot, leaving just the main stem and 4 to 6 branches around the bottom. To make sure that it doesn’t end up doubling over with the weight you should wire or string it, and you’ll have 16 extremely productive plants where before you could only fit 9.
Doubling over branches to stop growth and increase strength:
If you take one of the branches on your plant and bend it slightly, it should form a sort of callus which will double the strength of the branch. The cells in your plant will make their way to the injury and they’ll strengthen the branch, allowing it to put up with much more weight. As well as not growing any more, the end bud will have heavier buds. All you have to do is bend the branch slightly, making sure not to go too far; if you actually break it then that’s that. If done correctly, you should end up with thick balls of buds and compact, strong plants. You’ll be able to grow less plants in your grow tent but with a higher production rate.
What not to do when pruning your plants:
Pruning is essentially cutting a part of your plant so that it can direct its strength to other parts that can absorb light easily. This doesn’t mean that you can prune any part of your plants like the large leaves so that the light can reach the lower parts. Leaves have an extremely important part to play in your plants’ lives; they’re kind of like solar panels for plants, and the buds are the batteries. If light hits the batteries they won’t charge, it needs to hit the panels so that the light can be turned into energy for your plants. This means that if you remove the leaves you’ll end up removing a lot of the strength from your plants, as they act like nutrient deposits; if your plants leaves aren’t receiving enough light the plant will automatically absorb all of the nutrients, leaving the leaf yellow and dead.
None of the leaves are disposable, even the smallest ones. Every single one is needed so that they grow properly. If you want to test this out yourself, trim one of the big leaves while your plant is still in the growth phase. You’ll notice how the branch carrying that leaf will stop growing, and branches with all of their leaves will continue growing without any issues. The same thing will happen to the buds; if you remove a leaf so that the lower buds can get more light, the higher buds will end up dwarfed and a lot less potent, when they would have been much bigger than the lower ones to begin with.
Another thing that you mustn’t do is prune your plants while they’re flowering. Plants need a few days to recover from prune-induced stress, and it takes a while to decide where the new branch or central stem is going to grow from. You’ll need to prune at least 15 days before you switch your plants to the growing period or before summer begins for outdoor crops. You need to prune during the growth period every time, or else the start of the flowering period may be compromised.
You can prune to change your plants’ shape, but never prune at the top to allow more light to reach the bottom; the top is always more productive than the bottom even if you want it to get more light. The logical thing to do would be to prune the bottom so that the top can produce even more.
If you’re looking to learn how to do other kinds of pruning, leave a comment and we’ll do our best to add it on to the article.
Author: Javier Chinesta
Translation: Ciara Murphy