There are few things more frustrating than an overcrowded grow room. “Stretching,” the term used to describe the rapid growth of cannabis stems, is a natural part of the vegetative stage and is influenced by plant genetics, among other variables.

Unfortunately, stretching is a common perpetrator of low yields and lanky plants, resulting in teetering, physically unstable crops. Despite the threat it poses, stretching can be controlled by first examining the factors influencing its growth, then creating protocol to sidestep these issues. Controlling cannabis stretching requires an understanding of how plants interact with both their internal and external environments.

WHY DO PLANTS STRETCH?

There are several reasons why plants stretch, one of which has to do with the strains themselves. Genetics plays a pivotal role in determining the eventual height of sativas, indicas and hybrids. Whereas most indica strains are bred to grow shorter and bushier, sativas often experience significant stretching, sometimes growing six feet or higher in some breeds.

While stretching isn’t harmful in and of itself, dramatic stem growth carries the potential of significantly lowering the crop’s final yield between 20-30% overall. When considering strains for your next home grow, research the common height of each variety you plan to grow in order to gauge whether or not the strain experiences a dramatic flowering stretch.

LIGHT EXPOSURE

One of the main culprits of inordinate stretching of cannabis plants is lack of light exposure. Plants that are too far away from an adequate light source will respond by spurring stem growth to move themselves closer to the lamp. Especially in the presence of many other plants, sparse lighting can easily cause a grow room to become severely overcrowded, throwing off the steady progress of your crop and the ratio of distance between bulbs and plants.

In response to this issue, be sure to provide enough light to quell stem growth. At the same time, you don’t want to position your lights too close to your plants, as this will also result in overstretched stems and in some cases, lost yield.

In addition to distance between the source and the plant, the kind of light being used also holds influence over the amount your crop will stretch. Orange and red light encourages stretching and results in thinner, taller stems. Conversely, blue light stimulates thicker stem growth and a shorter height therein. When a strain is ready to enter the vegetative stage and undergo its most drastic period of stretching, metal halide lamps can be used to discourage extra-long stems.

HEAT

Heat is another pivotal element that can determine how much plants will stretch during vegetation. Temperatures reaching over 27 degrees push stems to grow longer and longer and will propel sativas to their full height potential. Heat lamps that are positioned too close to the plants creates an intolerable environment that will rouse tall, wobbly plants, which are likely to fall over and potentially lose flowers in the process.

Comparison Topping Cannabis plant

OTHER CAUSES OF STRETCHING

There are numerous variables that can lead to plants stretching beyond what is normally expected from the strain. Significant environmental stressors resulting from transplant may cause the plant to go into shock. This will then trigger a reaction, causing it to stretch. Cannabis plants that are not properly cultivated under decent conditions or aren’t receiving satisfactory nutrition will respond in a number of adverse forms, including stretching.

Crops that are not spaced far away enough from one another are likely to stretch as a result of competition for resources. Due to extreme proximity, plants will fight each other to reach the light, forcing growth throughout the crop.

HOW TO PREVENT STRETCHING

In many cases, you can account for at least some stretching to occur in the flowering stage of your cannabis plants. With this is mind, it’s helpful to establish a plan in case you're strain ends up growing higher than you imagined. If the information is available, obtain the average reported height of your strain and compare it to your grow room dimensions, considering the necessary distance between bulbs and plants.

CIRCULATION

While outdoor grow-ops benefit from the presence of the open air to naturally limit stretching, indoor operations are tasked with the tough assignment of maintaining air circulation inside a closed space. Sufficient airflow helps cannabis stems strengthen and grow thicker, rather than taller. This way, plants still grow vigorously, without reaching nerve-wracking heights.

MANUAL INTERVENTION

For those cultivators looking to get their hands dirty, there are physical intervention methods that can be taken to reduce over-stretching. Similar to the natural effect wind has on cannabis plants, manually bending the leaves and stems will cause tiny tears in plant tissue that will cause the plant to focus its attention on stem regeneration instead of vertical growth.

Bending branches cannabis plant stretching

TOPPING

Topping is a form of manual intervention on cannabis to affect its yield, shape or size. In essence, topping is the process of cutting of a new, actively growing node from your plant in order to reduce its size and create a “v” shape that will then form two colas. Topping can be an effective measure for combating stretching, but it’s important not to top once the flowering stage begins.

In most cases, unexpected stretching from cannabis plants won’t destroy your yield entirely. In fact, stretching can actually help to increase your yield. For cultivators with sizeable grow rooms that can sustain tall plants, stretching may actually increase a strain’s total yield with more vertical surface area for colas to form. Either way, stretching can be easily prepared for in advance and there are a number of different solutions to help with this all-too-common problem.

 

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