There are many cannabis plant training techniques, but only a handful have been used for decades and proven effective. Increasing yields, managing the canopy, and light efficiency are all reasons to practice techniques such as topping. Today we aim to demystify the most common plant training practice; how to top a cannabis plant.
Topping, low stress training, supercropping, sea of green, and scrogging are a handful of training techniques used by cannabis growers to control the overall form of the plant. Tall strains can be trained to grow out instead of up. Some growers will cut the top portion of the plant off to create a shorter and bushier plant. When growing a variety of cannabis strains in an indoor area, many times, cannabis training is required to keep the canopy as close to level as possible.
A popular technique often used in the garden is topping. Topping is the act of removing the upper portion of the plant. We realise it may be a little counterintuitive to remove the upper part of the plant; after all, that is where the big colas come from. Although it sounds crazy, your yield potential increases when you remove the top.
Plant topping is meant to maximise the quality of buds by creating multiple colas instead of one giant cola on the main meristem and increase yield. Again, it is the increased number of top bud sites that increases the yields when using cannabis training methods like topping.
Why removing the top of a plant can be beneficial
Three main reasons cannabis growers use topping as a training technique include space management, hormone distribution, and light efficiency. We will explain the “why” behind each of those statements, and how topping can lead to greater success in the garden.
When grown naturally, cannabis plants want to grow in a Christmas tree shape, with the lower branches reaching out the widest to receive unobstructed light. Removing the top portion means the lower branches are no longer shielded by the large fan leaves above. More light to more leaves equals more photosynthesis, and that means more power for the plant to grow and develop buds.
The technique of topping cannabis can also be used as a height management tool in small grow areas with low ceilings. Topping is also an effective training technique to create an even canopy. If gardeners grow a variety of cannabis strains and one of them grows much taller than the rest, topping that plant will bring it back to a level closer to the others.
Topping cannabis is an effective plant management tool if a gardener lets their plant get too tall in the vegetative stage. Most strains will nearly double in size during the transitional “stretch” phase as you begin the flowering cycle. If a plant is already close to the light source and you fear that it will grow above the light after the stretch, topping can tame that beast back into control.
There are a few physiological benefits to topping the plant. When a cannabis plant is topped, it is the lower branches that rise to create the canopy. These branches grow thicker and more robust, often requiring less support later. The primary physiological reason for topping any plant would be the redistribution of auxins and hormones when we break the apical dominance.
Instead of the auxins and growth hormones going to the tallest point, it is evenly distributed amongst the evenly level canopy. This promotes even growth across many bud sites instead of the single tallest point. By having more “top” buds instead of one large cola, yields can increase dramatically, particularly when combined with other plant training techniques.
Another reason growers want an even canopy is to maximise the amount of usable light (PPFD) delivered to the cannabis plant. A level canopy will distribute the same amount of light to as many bud sites as possible. When plants grow untrained, they can have a main stem far above the bulk of lower branches and bud sites.
To accommodate that taller top area, the grow light must be kept further from the majority of bud sites, which results in lower PAR to the bulk of the bud sites. With an even canopy, you can place the light closer to the majority of the upper bud sites.
Overall, when you top a plant (or even the many side branches), you will get two new branches in the place of the old one. Growers then have two bud sites, which is one way that topping can help increase yields. The change in distribution of growth hormones also encourages lateral branching in the plant. Combined, these two benefits result in a larger, bushier plant than one grown without topping.
When to top a cannabis plant
Topping a cannabis plant is almost always done in the vegetative stage. In instances of an extremely stretchy plant during flowering, topping might be the only option, but for the most part, topping cannabis is done in vegetation. Most gardeners will top a cannabis plant once or twice. This training technique can be performed several times, as long as the grower gives the plant a chance to recover in between.
Often growers will reference a node number as to when and where they top the plant. It is best practice to use your discretion. Commonly growers recommend topping between the 5th and 7th nodes. However, there can often be a difference in how tall a plant is by the 5th – 7th node, depending on an indica or sativa morphology. Know the height of the garden space, and the typical stretch of the strain, and top the plant accordingly.
Other growers will let the plant get further into the vegetative stage before topping a cannabis plant. The established root system helps the plant recover quicker compared to a seedling with a less developed root system. Growers may trim a few of the lower branches before deciding where to top. Removing some of the lowers will influence how many branches (nodal spaces) to leave before topping the plant.
In both cases, you want to only top a healthy plant, as this technique does induce some stress. Although the plant undergoes mild shock, with solid genetics, topping a plant should not trigger hermaphroditic expressions. Topping cannabis plants is the most prevalent of all plant training techniques.
How to top a cannabis plant
Growers will only need one tool to top the plant, a sharp, sterile blade. Many cannabis gardeners will use trimming scissors, and others will use a fresh razor blade. Similar to taking a clone, gardeners will want to make their cut at a 45 degree angle instead of straight across.
When topping a mature plant, make the cut 2-3 cm above the last node you want to branch out. The cut portion of the stem will dry and shrivel back slightly. Leaving this extra space will allow for that without compromising the strength of the branches on the uppermost node.
To count nodes, start at the first set of lower branches and go upwards. Each pair of branches above is a new node. Nodes are simply the location where a branch is attached, usually one branch on either side of it. When using this plant training technique, growers count the nodes on the main stem to make their decision of where to top.
Now that you’re ready
After topping the cannabis plant, give the freshly topped plant a few days to a week to recover from the shock. Don’t top a cannabis plant and then immediately put it into flowering. Keep the plant watered and fed; it is incredible what a healthy cannabis plant can handle regarding training techniques and stress.
By utilising this one easy plant training technique, you can have larger yields, grow different strains side-by-side, and maximise the efficiency of your wattage per euro.
Topping as a plant training technique is often used in combination with other techniques. LST (low-stress training) techniques, like bending branches or tying them down, is another way to deal with canopy management and breaking the apical dominance of a plant. The cannabis training technique referred to as “mainlining” is a combination of topping and LST.
Our goal is to lift the mystery behind these growing techniques and make them easily relatable to any gardener enjoying the hobby. We’ll be covering LST, supercropping, scrogging, and more in the upcoming plant training articles. What techniques would you like to know more about? Which plant training techniques are your favourite? Let us know down in the comments. Happy gardening!
- Disclaimer:Laws and regulations regarding cannabis cultivation differ from country to country. Sensi Seeds therefore strongly advises you to check your local laws and regulations. Do not act in conflict with the law.