Internodal Stretching


In this article, Gary Sigman of Metaphase Lighting Technology explains why cannabis can experience internodal stretching, and how to avoid it.

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Stretching is a natural characteristic for plants, but it can be a problem.


Stretching is a term used to describe what happens when cannabis stems experience rapid internodal growth. The phenomenon of stretching is seen in non-cannabis plants as well. Any grower knows that cannabis normally stretches during the vegetative stage and then slightly during the flowering stage. If the stretching extends throughout the flowering stage, then it is very likely that a grower will see lower yields and scraggly plants. This extended and unnecessary stretching makes the overall plant weaker; the infrastructure necessary to support a higher yield is not built, and the plant will bend or break under an increased load.

An example of stretching seen in a seedling.

The cause for extra stretch is typically inadequate light. Not only will inadequate levels of illumination cause stretching, but the wrong type of light can also cause the plant to behave like it’s poorly illuminated. The plant will grow longer stems to in an attempt to reach for more light. In the worst case scenarios, the plant may even try to reach above the light fixture. It is critical that the plant receives the right type and right amount of light throughout each growth stage. The correct spectrum during vegetation and flowering will bulk up the plant’s infrastructure, resulting in much larger roots and stems that can support an additional yield.

It is easy to see that stretching can be controlled in non-cannabis plants. I once worked with a soybean grower using supplemental HPS (8’ above the floor) in an open sky, glass enclosed greenhouse. Normal soybeans only grow to be 12″-18″ tall. His soybeans were stretching to 4′-5′ tall, trying to reach the sunlight. And because it was stretching, the stems were very weak, sometimes breaking during the growing process. Some of the plants were literally falling to the floor. Obviously this was a pure sign that the plants were not getting what they wanted.

He decided to change the lighting. He introduced broad-spectrum LED lighting about 1’ below the HPS fixtures. The new plants grew to 12″-18″ and bushed out, developing much larger roots and stems, providing the necessary infrastructure. The plants were able to support a larger yield. As a caveat, the designed spectrums for all the growing stages contained insect deterrent properties. Insects stayed away from the plants under the LED.

The broad-spectrum of the LED lights satisfied the plant’s need for light. The same phenomena was also experienced by our field-testing cannabis growers; there was little to no stretching during the flowering stage.



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Resources:

  1. Want to learn more about subjects touched upon in this article? Check out our articles on subjects such as:
    1. Physics: Fixtures as Lighting Sources
    2. How to Measure Horticultural Lighting Performance – Part One
    3. Using Light to Repel and Attract Insects
  2. Want to read more about the light Gary mentioned? Click here to see it.
  3. Want to get in touch with Gary Sigman? They can be reached via the following methods:
    1. Website: https://www.metaphase-tech.com/
    2. Email: [email protected]

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About the Author

I have been in the lighting business for over 20 years. Recently I became the Business Development Manager for the Metaphase Lighting “New Technology” products. I am regularly in contact with growers, researchers, and scientists throughout the US and the world.