Cannabis Training and Pruning Techniques
Savvy cannabis growers know that training and pruning their prized plants is imperative for maximum yields. Grubbycup goes through the various techniques that will surely help take your grow to the next level.
Cannabis naturally grows in a fat Christmas-tree shape, with a large central cola (apical meristem) on top, and smaller buds at the growth tips on the ends of the branches. While this shape is well suited for growing outdoors, indoors it can be helpful to have a more even canopy for lighting purposes. Buds create hormones called auxins which retard the growth of budding sites lower down on the plant. Auxin concentration also influences growth on the far side of a semi-shaded stem which causes cells to enlarge; this pushes leaves to face a light source (phototropism).
The top cola is the largest because it isn’t influenced by the hormone’s trickle-down effect, since there aren’t any buds higher than itself (known as apical dominance), and it inhibits the size of the buds developing below it. A similar effect can be noticed on individual branches where the terminal (end) buds grow larger than those closer to the stem. This is why, in nature, the top bud is the biggest, and the next largest buds occur at the ends of the branches. Growers can influence the flow of auxins from the growth tips to the rest of the plant through pruning or training to promote a more even canopy, bushier growth, and more uniform bud size. Methods introducing stress to the plant should be done while the plant is in growth to allow for easier recuperation and recovery.
Cannabis Pruning Technique #1: Pinching (Topping)
One way to keep the top growth tip (where the top cola will form in flower) from producing auxins is to simply remove it. This is commonly known as “pinching” because the tips are pinched off using a thumb and forefinger, allowing the next node in line to develop. Pinching is generally most effective with seed-started plants or with clones young enough to have pairs of budding nodes on either side of the stem. Pinching should be done in growth, as the plant will have to recover from the damage and adjust.
Cut just above the next two nodes and remove the top growth tip. The cut should be made just over the next two nodes in line as any higher stem section remaining will die off down to that point. Since the top cola has been removed, and is no longer producing auxins to inhibit their growth, the two (now top) nodes are free to develop into growth tips which will develop into two smaller colas instead of one large one. Once the plant has recovered and each of the two nodes are developing into branches, the process can be repeated on both branches to form a total of four colas. Each time the method is repeated it will form double the number of even shrinking bud sizes (two, four, eight, 16 etc.) Pinching can also be done with branches to help the plant have a bushier shape.
To put it another way; the removal of the apical growth tip from a stem allows the next two budding sites to develop better. The two new tops or ends will no longer be influenced by the missing growth tip and will split the advantage between them. Each will develop into a branch (and later in flowering a bud). Once each branch has developed a pair of nodes in addition to the growth tip, the growth tip can be removed to trigger each of those two nodes to develop into growth tips. This can be repeated to change a normally taller and somewhat lanky plant into a much bushier and compact plant. Instead of a substantially larger flower cluster at the top of the plant, a pinched plant will produce several smaller flower clusters (buds).
Generally, pinching is something best done in moderation, as overuse can reduce the size of each bud down to popcorn size which is generally not appreciated by anyone having to trim it.
Cannabis Pruning Technique #2: FIM (F%[email protected] I missed)
Fimming is a variation on pinching that involves removing just enough of the top growth tip to retard growth without removing the entire tip. This allows for the next growth tips in line to “catch up” to it while it recovers. This forms three growing tips instead of the two made via pinching. Legend has it the technique was developed by someone attempting pinching and not taking off the entire node (hence the F%[email protected] I missed).
Cannabis Pruning Technique #3: Lollipoping
Not all styles rely on removing (or moving) the top cola. The goal of lollipoping is to wind up with a single large bud on a stick (stem) like a lollipop. Any side branching is removed and plants are flipped from growth lighting to flowering earlier than with other techniques. This is commonly used with Sea of Green (lots of small plants grown quickly) methods.
Cannabis Pruning Technique #4: Brazilian
This is close to a multi-branched lollipop but less aggressive. With an even and full canopy, there exists a space below that won’t get enough light to be really productive. By removing the underlit foliage and twigs at the bottom of the plant, airflow can be improved and the poor-quality “popcorn” buds on lower stems can be avoided. This allows for the plant to focus its energy on the well-lit canopy above.
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Cannabis Training Technique #1: High Stress Training (HST, Supercropping)
The growing tip need not necessarily be removed to take advantage of auxin manipulation. If the top of the shoot is bent so it is no longer taller than the next nodes, then it loses much of its advantage over them. This is done by carefully weakening the stem by slightly crushing it between forefinger and thumb, and then bending until the branch is in horizontal line with the nodes to be encouraged. This method does cause damage and stress to the plant, and if done incorrectly can result in breaking off the branch being treated. High stress training is sometimes used as an emergency measure to correct individual branches that are growing too tall or too long.
Cannabis Training Technique #2: Low Stress Training (LST, Tie Down Training)
Low stress training is similar to HST, but instead of a sharp bend as a single point, as the plant grows new growth is trained as desired while it is still pliable using string or twine. This avoids the stress and damage associated with supercropping by instead nudging the plant’s growth in the desired direction, but at the cost of being more labor intensive.
Cannabis Training Technique #3: Screen of Green (SCRoG)
Screen of green is a form of LST where netting is strung in a flat horizontal plane and branches are trained so the growth tips (and later buds) are all at the same height. If done methodically, SCRoG can be fairly labor intensive, but benefits can be had even without perfection in the training.
Which method or combination of methods is best depends on the situation and desired results. Lollipopping is often combined with Sea of Green because each plant only forms a single bud. Mainlining uses a combination of pinching and LST. Screen of Green(s) are usually given a Brazilian as well to avoid creating a damp and still area under the screen. Most of these methods were developed to flatten the canopy for even lighting under lamps hung above the plants, however, different lighting situations may call for different training/pruning solutions.