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How to Control and Prevent Cannabis Plants From Stretching

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Added 28 April 2023

After you have found the cannabis seeds for sale that you want and germinated them, then the real challenges begin. Many growers assume that the seedling stage is relatively plain sailing, but there are several issues that arise.

Master the Seedling Stage

Master the Seedling Stage

The structure of cannabis plants is significant because it supports the weight of the blooms. As a result, a mistake at this point might harm the crop. Cannabis plant stretching can be a serious issue for proper development. If it’s not resolved promptly, it may encourage weak plants, resulting in a destroyed yield.

The extended vertical expansion of cannabis plants throughout the growth and blooming periods is known as cannabis plant stretch. Indoor gardeners attempt to prevent this since it weakens plants and causes other issues such as lower yield, less indoor space, lengthy internode distance, and different dangerous situations.

An Overview of Cannabis Plants Stretching

An Overview of Cannabis Plants Stretching

There are few things more aggravating than an overloaded grow room. "Stretching," the phrase used to describe the fast expansion of cannabis stems, is a normal aspect of the vegetative stage and is affected by plant genetics, among other factors. However, stretching is a typical cause of low yields and slender plants, resulting in unsteady, physically unstable harvests.

Despite the hazard, stretching may be handled by identifying the elements controlling its growth and then devising a plan to avoid these concerns. Controlling cannabis stretching necessitates understanding how plants interact with their internal and external surroundings.

Various Reasons Why Cannabis Plants Stretch

Various Reasons Why Cannabis Plants Stretch

Cannabis plants stretch for various reasons, one of which is related to the strains themselves. Genetics is crucial in influencing the ultimate height of Sativa, Indica, and hybrid strains. While most Indica strains are engineered to grow shorter and bushier, Sativa strains frequently stretch, reaching six feet or more in some breeds.

While stretching isn't inherently damaging, excessive stem growth can drastically reduce the crop's yield by 20-30%. Therefore, when selecting strains for your next home grow, look at each variety's average height to see whether the strain has a spectacular flowering stretch.

  • Heat

Heat is an important factor that influences how much plants stretch during vegetation. Temperatures above 27°C cause stems to grow longer and taller, propelling Sativa to their peak height potential. Conversely, heat lamps that are too close to the plants generate an unpleasant climate that may stimulate tall, shaky plants, causing them to fall over and lose blooms.

  • Light exposure

Lack of light exposure is one of the leading causes of excessive cannabis plant stretching. Plants that are too far away from a good light source will respond by increasing stem growth to migrate closer to the bulb. Inadequate illumination can easily lead a grow room to become excessively congested, throwing off the steady growth of your crop and the ratio of space between bulbs and plants, particularly when there are many other plants.

  • Other reasons for stretching

Various factors might cause plants to grow above what is generally anticipated of the strain. For example, significant environmental stresses caused by transplantation may cause the plant to fall into shock. This will set off a chain reaction, forcing it to extend. Cannabis plants that haven’t grown adequately or are not receiving proper nourishment can respond negatively, including stretching.

Crops not sufficiently separated from one another are prone to stretch due to competition for resources. Plants will fight each other for light due to their proximity, forcing development throughout the plant.

How to Prevent Your Cannabis from Stretching

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In many circumstances, you might expect some stretching throughout the blooming period of your cannabis plants. With this in mind, it's a good idea to make a strategy if your stress levels rise above your expectations. First, be aware of the average stated height of your strain and compare it to the size of your grow space, considering the necessary gap between bulbs and plants.

  • Select Suitable Genetics

Some cannabis strains stretch more than others, and the Indica or Sativa split isn't adequate to forecast a plant's stretching ability. Fortunately, all hope is not gone. Therefore, purchasing stable seeds from a respected seed bank is better as you can expect predictable outcomes. 

The seed bank will usually note any unusual behavior connected with a good or negative strain that the grower should know. So, if you're short on room or want to keep things under wraps, stick to trustworthy cannabis seeds that aren't projected to grow into super-stretchy plants.

  • Enhance light intensity (without burning the plants)

This method is efficient, but you must exercise caution to prevent harming your cannabis plants in other ways. Since your cannabis plan will naturally reach toward the sun, minimizing the distance between the canopy and the light source will lead to less stretching.

Various distances between the lamp and the canopy are recommended depending on the type of light. Keep your cannabis plants at the lower end of this spectrum to maximize sunlight exposure without scorching them or slowing their development.

  • Air circulation

Most cannabis plants remain erect and anchored in the soil when grown outside, despite the somewhat unpredictable factors at work. Unbelievably, a gentle breeze may strengthen the stem's inside by creating microscopic cracks that gradually increase the stem's thickness and stiffness. Additionally, this wind will contribute to preventing vertical growth.

  • Train your cannabis plants

If your plants aren't responding to your demands to stop stretching, or if you're about to embark on a major blooming stretch, some extra hands-on care may be required. Training and pruning allow you to shape your plant by minimizing vertical growth and controlling development.

LST may be used to promote lateral development and adequate light exposure, or you might take it a step further with a ScrOG, which is essentially an advanced type of LST. As your cannabis plant progresses from late vegetative to early bloom, you might route its branches through a mesh screen to optimize cannabis bud development while encouraging nearly lateral growth.

  • Allow adequate space between your cannabis plants

Unless you grow in a SOG, ensure enough room for plants to grow freely. If a plant lacks lateral space, it may compensate by growing vertically. Appropriate spacing is vital while growing cannabis plants since it promotes air circulation, giving plants ample breathing area.

  • Keep the temperatures in check

Temperatures above 29°C are also problematic for stretching; heat causes cannabis stems to become spindly and weak, and it may induce stretching on its own or worsen an existing problem. This is why, in addition to maintaining correct grow room temperatures, you should ensure that hot lights do not burn your plants.

A thermo-hygrometer is always beneficial to have on hand so you may constantly check the environmental parameters of the growing area. Cannabis thrives at different temperatures during its life cycle, so keep it within the optimal range.

Summary: How to Control and Prevent Cannabis Plants From Stretching

In conclusion, there are various ways to prevent your cannabis plants from stretching, but it all starts with genetics. In addition, it's common for cannabis plants to stretch a bit during the blooming phase. Therefore, make sure you purchase good seeds from reputable seedbanks and plan in advance before you start growing seeds. 


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No mention of Red light to Far-Red light ratio? A higher amount of far-red (IR) light activates the shade avoidance system which is mostly stem elongation for cannabis. Watch the video "Far-red: The Forgotten Photons" by Bruce Bugbee for details.