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Pruning for Yield

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Pruning for Yield

Pruning for Yield

Novice growers are infamously cautious about pruning. Possibly it’s since it appears wrong to hack away at a perfectly healthy plant– or maybe pruning is erroneously linked with pure looks? Whatever the reason, pruning is perhaps more crucial indoors than anywhere else. We asked Kevin Anderson, a grower in British Columbia, Canada, to share his wisdom on the art of pruning light-loving plants indoors.



Okay, let’s begin with a basic truth. Cultivating indoors is different to growing plants outdoors. The biggest difference is the light. Light, as we understand, is the ‘motor’ that drives the entire growth and bloom process. When growing outdoors, the Sun provides all the light our plants need. Indoor cultivators normally depend on high intensity discharge (HID) lights for the energy needed for photosynthesis.


But that’s just the start of the tale. The differences between the properties of the Sun and your 1000W High Pressure Sodium expand light are so numerous that comparisons seem ludicrous. The Sun is 93 million miles away from your plants whereas your indoor lights are simply a few feet! The intensity of the light from your grow lights decreases greatly the further your plants are placed away, whereas a couple of added inches or feet does not make any difference to the energy got from the Sun. Furthermore, if any part of your plant is too close to your grow lights they will quickly become heat stressed / burnt.

Pruning for YieldLight intensity lowers exponentially with a linear increase in distance from the indoor light.

So if you wish to grow light-loving plants indoors, you should address this crucial concern: how do you get enough light energy to your plants without triggering them heat stress? Many indoor gardeners hang their grow lights above their plants, utilizing a reflector to direct light down towards the canopy. The inverse square law informs us that if you double the distance between your plants and your light, the intensity of the light striking the plant is quartered.


The ‘sweet spot’ is the ‘not too near, not too far’ space under the grow light that gets the most light energy without being so near the light that the heat from the light meddles with the plant’s wellness and metabolic process. The objective of the indoor gardening game is to shape and place your plants so that as numerous development tips / bud sites as possible are basking in the ‘sweet area

The sweet spots’s distance from the light depends on the size of bulb you are making use of, the reflector (if utilized) and whether your lamps are stationary or mobile. Lights on a rail or rotational gadget can be put closer to plants because, as they are relocating, there is less danger of hot spots establishing. When it come to fixed lights and in the absence of a light meter, I hold the back of my hand under the light and move it away until it feels comfy and does not constantly get warmer: this is exactly what I call the ‘sweet spot.’ Regardless of my less-than clinical technique, there is absolutely nothing  mystical about this. You should get your grow lights as close as feasible to your plants without frazzling or stressing them. Experience counts for a great deal here! Your objective, as an indoor cultivator, is to control your plants so that as many bud sites as possible end up in the ‘sweet zone’ so they can mature and ripen to their full potential, basking in high light levels at the optimal temperature level.

Now we have the basis of an understanding of why pruning and control strategies like flexing and topping might be so vital to indoor growers. It’s all about getting as much of your plants buds into that ‘sweet spot’ as soon as possible!


Whenever a plant grows roots, stems, leaves, flowers, fruits it takes ENERGY. The rate of a plant’s development is restricted by the amount of light (ENERGY) it receives. This energy is distributed throughout the plant in order to bloom and grow. The objective of pruning is to concentrate this energy to where it’s most required– the bud sites in the ‘sweet spot area’.

What happens if you don’t trim, top or flex? What’s wrong with just letting your plants do their thing? Left up until the plant, whatever energy is gotten from your lights will be concentrated where auxins (plant hormones that regulate growth) are most present. Auxins will constantly gather at the top of the plant and wherever they collect grow more  keeping the top of the plant at the top!

Pruning for Yield Picture of a cutting left to grow into its natural form under an grow light.


In the picture above, the top of the plant is too near to the grow lamp and will rapidly begin to deal with heat stress or burning. This will stunt the development just at the point where all the bud activity needs to be!  At the same time the lower branches of the plant are not receiving much light. We can raise the grow light,  however this will mean that the lesser parts of the plant are going to suffer even lesser light.


The issue is the shape of the plant. Tall and triangular, like a Christmas tree, might match the Sun, but it doesn’t fit an grow light shade hung from above! The plant doesn’t understand that it’s in a completely different situation to outdoors, so it’s simply doing what millions of years of evolution have set it to do. It ‘thinks’ it’s growing under the sun, where light intensity up and down the plant is much more uniform. Topping, flexing, and low stress training (LST) are all manipulation strategies that the indoor cultivator can use to engineer the shape of their plants so that they can most effectively exploit these valuable grow light photons. The aim of pruning and flexing is to redistribute auxins with numerous shoots, therefore encouraging the plant to produce a variety of equally dominant branches and lots of buds instead of just one large top bud.


Numerous indoor growers make use of pruning and various other control strategies to engineer squatter plants with wider canopies like a candelabra. A larger, even canopy allows for more grow tips and bud sites.


Topping refers to the practice of getting rid of the top of a plant. This promotes the growth of the satellite growth ideas and a bigger canopy. I use a clean, super-sharp scalpel to top my plants. If topping multiple plants, clean your chosen pruning tool in between cuts with some rubbing alcohol. It sounds a bit anal, but you would not desire a surgeon to use the same instruments on you that they ‘d made use of  on the previous client, would you? Various cultivators top their plants at different phases. When the plant is really little (e.g. at the 4th internode) or when they are a foot or more high,  Typically speaking, plants take at least a couple of days to recover from topping and resume previous growth rates.


‘Pinching out’ is another term you may have come across. This describes the act of getting rid of a new growth tip, instead of the stem. I’ve appreciated my highest degrees of success by pinching out the lead development tip a couple of days before starting blooming. This is just enough time for the plant to recover from the stress of the growth tip being removed and redistribute the auxins. The plant will then start to branch off, leading to a more even canopy with even more tops.

Pruning for YieldThe exact same plant after being topped at the eighth internode. Compared to the untopped plant, it has many more bud sites in the sweet spot with no extremities erring too close to the hot bulb.


Note: topping is not suited to all plant selections or cultivars. If you are not sure how your plants will react, attempt it on some cuttings first and compare results. Don’t simply compare yield but compare bud quality and size too!


Pruning for YieldxxxThe same topped plant, however now with lower branches removed to concentrate bud growth in the ‘sweet spot.



The ‘tidy up,’ as I like to call it, is an additional kind of pruning that is commonly practiced by indoor gardeners. Once again, it’s about concentrating the plant’s energy into fewer, bigger, better quality buds. If left to its own devices, a light loving plant grown indoors will normally produce lots of little, reduced quality buds, especially on the lesser branches. This is because of reasons already mentioned specifically: the light from a HID bulb loses intensity and does not penetrate the dense canopy above. Bear in mind, these lower yielding regions will still draw from the plant’s limited energy reserves and frequently the buds take longer to mature. With a prompt removal of the lower down, shaded growth and spindly branches, the plant has less potential bud sites over which to spread its energy. It still has the exact same quantity of energy (as long as not too much plant matter was gotten rid of in pruning), and there is still a thick canopy to bask in the full light; however, this energy is also now concentrated on a lower lot of bud sites resulting in even larger, greater quality buds. Pruning off the bottom of the plants and removing congested branches has the extra advantage of creating better air-flow through and under the plants, assisting to avoid conditions which promote molds.


Most strains of cannabis will experience a development spurt during the transition in between vegetative growth and blooming (generative) growth. I think the very best time for the tidy up is immediately after this preliminary ‘stretch’ (but prior to the plant starting to flower). The plant will stretch even more and become rather leggy if too much is pruned off too soon. If you tidy up too late, you will be removing green matter that the plant has actually currently invested a great deal of energy into. The later you trim into the flowering stage, the more the plant is focusing its energy on generative development instead of vegetative. A good guideline is to “tidy up” the plant in the second week of flowering simply as the first little indications of bud appear and after the plant has actually stretched a little.

Here is a nice video which shows some of the techniques the good bit starts about 2 mins into the vid[covertplayersinglevideo trvideoid=”UbGHqxNMAhs” trdisplaytype=”5″ trnumbervideosdisplay=”” trvideoperpage=”36″ trthumbnailwidth=”125″ trthumbnailheight=”125″ trpopupwidth=”500″ trpopupheight=”350″ trvideoalign=”left” trytautohide=”0″ trytautoplay=”1″ trytcontrols=”1″ trytrelvideo=”0″ trytshowlogo=”1″ trytshowtitle=”0″ tryttheme=”dark” trythighquality=”0″]

There is a fine line in between pruning off too much and winding up with a really sporadic canopy and a loss in yield, and leaving too much on and decreasing the size and quality of the buds. This takes some experience. There are lots of variables to consider: plant selection, plant density, veg times, etc. Less pruning is required for plants that have even more area; even more pruning is needed for denser gardens.

Pruning for Yield

Attempt to get an even canopy with an abundance of flowering tops basking in the sweet spot!

Typically, I often prune off all branches lower than a third of the way up the plant. As the plants begin to flower you should have the ability to crouch down and peer right through your garden, underneath the dense canopy. Prune off weedy smaller sites 2/3 to 3/4 of the way up the plant on the less dominant branches, and about halfway up the plant on the dominant branches so there is a slightly sporadic canopy. This could appear a little too much at the time, however the plant is still growing quite substantially and will fill in a lot before it finishes stretching.


I hope this post has given you a few tips on pruning to yield as always comments are welcome and encouraged. Cheers!




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