Low-stress training (LST) is a method used by growers to control the height and shape of cannabis plants. For newbie growers, it's a useful technique that can increase crop yields and round out cultivation skills.
What is low-stress training?
Low-stress training enables growers to fully exploit the available space and light by manipulating the growth pattern of plants. Cannabis plants tend to grow into a formation known as apical dominance, where the plant is bushier at the bottom and narrows to a single elongated cola at the apex. This natural formation tends to result in a single dominant bud at the top of the plant, which monopolizes nutrients and hormones, leaving smaller buds on the lateral branches.
The purpose of LST is to encourage the plant to flatten at the canopy, thus providing more even access to light, and multiple thriving bud sites. This constriction allows sugars and the growth hormone auxin to distribute more evenly. By flattening out the canopy, the entire plant also receives more light, promoting the growth of more buds and larger yields.
LST is usually carried out during the vegetative phase while the stem and shoots are still pliable. The cannabis plant begins to grow in a circular pattern rather than straight up. When the plant enters its flowering stage, healthy colas will sprout upwards from the sideways-growing plant.
LST involves gently bending and tying strategic branches and stems. The technique decreases the risk of over-stressing the plant, allowing it to adjust to the training measures and adapt more rapidly. For those unwilling to try or unfamiliar with high-stress training techniques, low-stress training is a low-risk practice to which plants generally respond favorably.
LST can be used on both indoor and outdoor plants, optimizing space and maximizing bud output. For outdoor cultivators, it can help to keep a crop low profile.
How is low-stress training performed on cannabis plants?
LST can be initiated when the plant's stem and shoots become long enough to be tied down. Make sure you use stretchy plant tape, pipe cleaners, or rubber-coated wire as they are more gentle on shoots and stems. Regular wire or string should be avoided as it may cut into the stems as they grow, causing damage.
- The first step is to create several small holes around the rim of the plant container. Some growers even insert a tomato ring at this stage. Tomato rings can be useful if the plant becomes significantly larger as it grows. The ties will be looped through the holes or attached to the tomato rings, then secured to the shoots.
- Bend the main stem and gently secure it to the rim of the container. Many cannabis growers tie the stem in a circular shape around the container as it grows so it begins to coil like a snake. Other growers choose to bend the shoots outwards away from the stem, securing the shoots to the holes in the container with ties. The plant then begins to take on a spider-like appearance.
- Make sure you bend the shoots or stem gently. It's helpful to have duct tape on hand in case there are any accidents--the tape can be used to hold together any snaps or breaks. Cannabis plants are reasonably robust, so there's no need to be overly concerned about a broken shoot as it can heal.
- Some light defoliation, or removal of leaves, in the beginning can maximize light penetration.
- LST is a process. As new shoots appear, they will need to be bent and tied down. As the shoots grow larger and more leaves appear, the bends may need to be periodically adjusted to keep the canopy even.
Another type of low-stress training: the screen of green
While you can gently bend and tie down long branches, there are other methods of carrying out low-stress training. The Screen of Green, or ScrOG, facilitates low-stress training with the use of a screen. The ScrOG low-stress method encourages horizontal growth as it forces plants to grow through a suspended screen. When the branches begin to reach through the screen, they are simply tucked back underneath. Vertical growth is inhibited, and the growth spreads to the side branches in response, encouraging bud sites to form in areas that would have otherwise been dormant. Like low-stress training, ScrOG helps optimize yields.
Can you low-stress train in the flowering stage?
LST is most commonly performed during the vegetative period when the shoots are pliable and the plant's growth can be more easily directed. That being said, low-stress training can also be used during the flowering phase. Bending stems during flowering can help ensure even exposure to light. For growers looking to redistribute the plant's energy from many growth sites to a few, the first couple of weeks of flowering can be a good time for low stress training.
LST is generally not initiated on plants that are mature and fully flowering. Constant LST, however, throughout both the vegetative and early flowering phases, can help keep mother plants healthy and capable of producing robust clones.
When can you start LST?
It's a good idea to begin low-stress training as soon as the plant is in the vegetative state and has established several robust nodes. When the shoots and main stem reach a length where they can be bent and fixed, LST can be easily carried out and will yield the best results. Waiting until later in the vegetative or flowering cycle can become problematic as the stems and shoots can become too rigid to bend.
How do you train autoflowering strains?
Autoflowering cannabis plants grow rapidly as they do not require a change in light to commence flowering. High-stress training methods can cause problems for autoflowering strains as their two-to-three month life cycle leaves little time to recover from damage. Low-stress training methods, however, represent an ideal way to manipulate autoflowering plants and maximize their yield.
Since flowering can begin in as few as two to four weeks in autoflowering cultivars, LST should begin earlier to reap the benefits. The technique provides the same benefits for autoflowering cultivars as photoperiodic ones - it can help spread and even out the canopy and encourage more abundant, denser colas.