Pruning Cannabis during vegetative stage.

Pruning cannabis and training cannabis are common usages. Tomato growers pinch out side shoots, giant pumpkin aficionados remove all but one flower. Cannabis growers too have their own preferences for optimizing their marijuana bud potential.

 General cannabis pruning and training tips:
  • always use secateurs or sharp knife to avoid bruising
  • when using ties, leave them loose enough to allow for plant growth but tight enough to support the stem.


We´ll explain the various methods of pruning and how each one effects your plants later in the article. First though, a few questions we often get asked –

Pruning during flowering?

Its generally to be avoided. Once you have flipped to flower at a cellular level the plant’s energies are no longer focused on growth but are making the transition to creating bud sites and later developing flowers. Pruning cannabis during veg works because the “cut” controls and diverts the growth hormones (see apical dominance in this piece on supercropping). Once the transition to flowering has been made, these growth hormones are hardly produced: in order to repair the damage caused by pruning, the plant has to divert energies away from bud production and into making growth hormones instead. This HAS to have an effect on total yield. There is a 10 days grace period (during pre-flower stretch) when the plant is still growing and beginning to flower when you can get away with it, but certainly after this point: DON’T!!!


What about trimming shade leaves during flowering?

This is one of the most contentious practices among marijuana growers. Its very popular say in Spain where even the tomato growers remove large shade leaves during the flowering stage. The theory is that these leaves draw energy away from the buds and may indeed accelerate flowering maturation.And yes, we have seen some youtube vids and grow reports of plants almost fully stripped of leaves that look quite good.

BUT science tells us that pruning cannabis for maximum yield means avoiding pruning during flowering. The large fan leaves photosynthesize the energy needed for good buds, and even as the plant matures and the leaves turn yellow, it is better to let these gradually reabsorb the energy rather than shock the marijuana plant by pruning them. Leaf removal may even prompt sex change.

Here’s what the expert says:


Leafing is one of the most misunderstood techniques of drug Cannabis.cultivation. In the mind of the cultivator, several reasons exist for removing leaves. Many feel that large shade leaves draw energy from the flowering plant, and therefore the flowering clusters will be smaller. It is felt that by removing the leaves, surplus energy will be available, and large floral clusters will be formed. Also, some feel that inhibitors of flowering, synthesized in the leaves during the long non inductive days of summer, may be stored in the older leaves that were formed during the non inductive photoperiod. Possibly, if these inhibitor-laden leaves are removed, the plant will proceed to flower, and maturation will be accelerated. Large leaves shade the inner portions of the plant, and small atrophied floral clusters may begin to develop if they receive more light. In actuality, few if any of the theories behind leafing give any indication of validity. Indeed, leafing possibly serves to defeat its original purpose. Large leaves have a definite function in the growth and development of Cannabis. Large leaves serve as photosynthetic factories for the production of sugars and other necessary growth sub stances. They also create shade, but at the same time they are collecting valuable solar energy and producing foods that will be used during the floral development of the plant. Premature removal of leaves may cause stunting, because the potential for photosynthesis is reduced. As these leaves age and lose their ability to carry on photo synthesis they turn chlorotie (yellow) and fall to the ground. In humid areas care is taken to remove the yellow or brown leaves, because they might invite attack by fungus. During chlorosis the plant breaks down substances, such as chlorophylls, and translocates the molecular components to a new growing part of the plant, such as the flowers. Most Cannabis plants begin to lose their larger leaves when they enter the flowering stage, and this trend continues until senescence. It is more efficient for the plant to reuse the energy and various molecular components of existing chlorophyll than to synthesize new chlorophyll at the time of flowering. During flowering this energy is needed to form floral clusters and ripen seeds. Removing large amounts of leaves may interfere with the metabolic balance of the plant. If this metabolic change occurs too late in the season it could interfere with floral development and delay maturation. If any floral inhibitors are removed, the intended effect of accelerating flowering will probably be counteracted by metabolic upset in the plant. Removal of shade leaves does facilitate more light reaching the center of the plant, but if there is not enough food energy produced in the leaves, the small internal floral clusters will probably not grow any larger. Leaf removal may also cause sex reversal resulting from a metabolic change. If leaves must be removed, the petiole is cut so that at least an inch remains attached to the stalk. Weaknesses in the limb axis at the node result if the leaves are pulled off at the abscission layer while they are still green. Care is taken to see that the shriveling petiole does not invite fungus attack. It should be remembered that, regardless of strain or environmental conditions, the plant strives to reproduce, and reproduction is favored by early maturation. This produces a situation where plants are trying to mature and reproduce as fast as possible. Although the purpose of leafing is to speed maturation, disturbing the natural progressive growth of a plant probably interferes with its rapid development. Cannabis grows largest when provided with plentiful nutrients, sunlight, and water and left alone to grow and mature naturally. It must be remembered that any alteration of the natural life cycle of Cannabis will affect productivity. Imaginative combinations and adaptations of propagation techniques exist, based on specific situations of cultivation. Logical choices are made to direct the natural growth cycle of Cannabis to favor the timely maturation of those products sought by the cultivator, without sacrificing seed or clone production. Cannabis Botany from R.C. Clark.[/su_tab]

Can you prune an autoflowering cannabis plant?

Well yes you can. We’ve regularly “topped” (see stem tip removal below) autos to produce a bushier plant. What you’ve got to remember though is that there’s only a short period of time in which to do this – but if you are growing a 10 week plus seed to harvest autoflower, you can get away with pinching out at the 4th set of leaves, and again at the 5th before the plant naturally makes the transition into flowering.

Read more about pruning autoflowers here

To find out about the different pruning techniques, go to page 2

6 thoughts on “Pruning cannabis

    • campo cultivator says:

      Thank you for the kind words. We try our best! I would however disagree with Eric with regard to pruning a few weeks into flower: by this stage I always find it better to let the plant devote its energies into bud production rather than dealing with stress and cell repair at this stage. Readers might also like to read more about pruning in our piece on supercropping which goes into the principles behind pruning a little more

  1. Red says:

    I understand there are different views about pruning during different stages,etc. It’s actually the same way for alot of other plants indoor n out. Has alot to do with the one actually tending to them. I’m one who feels since they breath, they live as we do w basics plus compassion.
    Anyhow- new to the whole grow thing n very perplexed the last few weeks. Our ladies r in their (technically) 11th wk. 12 starts tomorrow. Anyhow, SUPER long story short (trust me, it’s a very screwy situation) our ladies r finally starting to pop. However holy crap r they super super thick w leaves. Smaller fan leaves, big deal; but the long slender dark ones r everywhere. These ladies have been handled through out their life. Pruned of hand size fans n spotty growth on trunks w nice temps, pretty good air flow (we think/hope) n plenty of water. Light at times has been an issue but addressed as quickly as possible. BC of growth spurts, they are incredibly tall w new flowering growth up by lights- which by the way can not possibily go up any further.
    I just don’t truly know what to do w all the leaves. Really big or heavy ones I have been taking, but the plants r so thick in foliage along w bud sites that I don’t feel there is enough light getting to the buds in the middle of the bushes. Will our buds still swell n thicken up or should we snip more space for them to breath?
    Oh n pop quiz: any ideas about stunted growth. The buds r not exploding w mass. They’re closed lavendar Jones.

  2. Billy Madison says:

    Defoliate is that simple I have been doing it for over 20 years it does not stunt the plant it actually increases in growth once the node has started to grow out an inch or so…. Remove all fan leaves that would be blocking your bud sites plant should bounce back within 2-3 days with rapid growth.

  3. Davie says:

    I never pruned leaves in the flowering stage but I did give it a go with my last lot which had 9 wk flower time, it didn’t go well and even paused their growth and looked as though they went back into veg. They ended up finishing in 14 was, SO DONT PRUNE IN FLOWER.

Leave a Reply

Your email address will not be published.