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How to Prepare Marijuana Plants For the Flowering Stretch



Much like human beings around the time they hit middle school, stretching is a natural growth-spurt for cannabis plants. This is “an explosion of vertical growth” which most of the time adversely affects the outcome of the cannabis crop. 

There are very few things that are more frustrating to a weed farmer than a grow room that is overcrowded. Unfortunately, stretching happens to be a very common perpetrator that spikes low yields, and lanky plants. The plants that have been struck by stretching are often teetering, and physically unstable crops. In this article, we will delve into the causes of stretching and how it can be prevented from taking over your grow room, and messing up your yields.

What Causes the Flowering Stretch?

There are various reasons why cannabis plants stretch, and we will look into each of them in-depth. However, genetics plays a vital role in determining how much stretch a particular strain will experience. The eventual height of indicas, sativas, and hybrids is often dictated by these sub-types. 

The Sativa Stretch 

Typically, a good number of indica strains are usually bred to grow out in a shorter and bushier stance. Sativa on the other hand typically grow very tall and are prone to experience significant stretching as they sometimes grow to up to six feet or even higher in some breeds.  

While stretching in itself is not harmful, dramatic stem growth could lead to significantly lower crop yields of up to 20-30% overall. When you are caring out the research for the next strains you want to grow, take into consideration the eventual height of the strains you pick, and therefore how dramatic their flowering stretch is bound to be. 

Causes of Excessive Stretching in Cannabis Plants

Though you expect your cannabis plants to stretch some, especially during the “flowering stretch”, there are times when they stretch excessively, even beyond this period. There could be numerous variables which could lead to plants stretching far beyond what would be normally expected of that strain. Some of the reasons for too much stretching are:

  • Lack of light exposure is a huge contributor to inordinate stretching. Plants that tend to be too far away from adequate light usually respond by spurring the growth of their stems to get themselves closer to the source of light. This is usually even more common when several other plants are trying to access that light. This could cause your grow room to become overcrowded as well as hinder the progress of your crop as well as the ratio of distance between the plants, and bulbs. 

It is thus important to provide adequate light as well as position your lights adequately. In general, orange, and red lights encourage stretching while blue lights make for thicker stems and short heighted plants. 

  • Heat is another factor that plays a huge role in determining whether a cannabis plant will stretch too much during the vegetation period. If temperatures are kept at 27 degrees, the plant stems grow longer and even sativas are propelled to reach their full height potential. In the same breath, heat lamps which are positioned too near the plants also create an intolerable environment that will rouse tall, wobbly cannabis plants which will be likely to fall over potentially losing flowers. 
  • If the plant experiences significant environmental stressors which could result from the transplant, the plant may go into shock which would trigger a reaction that could lead to abnormal stretching.  
  • Cannabis plants which are not cultivated properly under decent conditions, and are probably not receiving satisfactory nutrition, could also respond in different adverse forms including stretching. 
  • When crops are not spaced far enough away from each other, they could experience stretching in a bid to compete for resources. 

Cannabis Stretching During Flowering

Depending on what strain you are growing, a wide range of stretching can be expected. In some strains, stretching will lead to the literal doubling of height while in some, not much will be observed. It is always advisable to check up the strain you are breeding so that you can know what to expect. Additionally, you can take into consideration the following factors to ensure you are well prepared:

  • Sativas – Sativas will almost definitely grow taller than indicas, you should therefore prepare for this. 
  • Strain height – Most breeders as well as seed banks indicate the average height they expect their strains to get to. It could be as vague s “tall, short, or medium”, but it will certainly give you an indication of how much stretch to expect. 
  • Light type – The type of light you pick will have an effect on how much your plants will stretch. We will however cover this more in-depth later. 
  • Light distance – As we have discussed, plants also tend to stretch when they are striving for more light. These plants grow taller but have fewer buds, and less yields. It is important to note that this kind of stretching is not inspired by the flowering stage rather than by a deficiency.

One of the reasons why it is so important to enlighten yourself about stretching is that rapid growth can reduce the space you have in your grow area. This will leave you with no space to raise your lights, which will lead to heat/light stress and a loss of buds. 

Cannabis Week 1 Flowering

The stretching that occurs during the flowering period is the most rampant one. Week one is when your plants will make the transition from the pre-flowering, to the full flowering stage. In this transition, some strains double their height in periods that could be as short as one week. Due to this rapid growth, the first week of cannabis flowering is often referred to as “the stretch”. 

When Do Weed Plants Stop Stretching During Flowering

Though this is not standard for every cannabis plant, the stretch period usually lasts between the first to third or fourth week of the 12/12 period. 

How to Flower Weed Plants To Control Flowering Stretch

The flowering period of cannabis plants is both induced by using flowering stimulants and adjusting the light cycles to a 12/12 cycle to spur the plant to go from the vegetative to the flowering stage. To both cater for and ensure that you are prepared for the flowering stretch, you can take the following measures::

  1. Measure the vertical height of your growing space in inches or cm. 
  2. Take that total and subtract the height of your lights at their highest point. 
  3. Next, subtract your pots/container’s height in which your plant will be grown. 
  4. Finally, subtract the total amount of space you will require to maintain between your light, and your cannabis plants. Note: This will vary according to the lights. CFL’s may need roughly only about 4″, while HIDs may need 12+”.
  5. Measure your plants until they get to half of your remaining number. Initiate flowering at that point!

This is a simple way to ensure you have things under control.

How to Stop Stretch in Flowering

As we have discussed, stretching is not always advantageous for the grower. In cases where you need to reduce the stretch of your cannabis plants, you can do adjust the following factors: 

  • Circulation  – Adequate air circulation encourages the growing of thicker, rather than taller cannabis stems. Plants grown on the outside have proper air circulation, and they therefore regulate their stretch adequately. However, for plants growing indoors, it is vital that proper air circulation is maintained. 
  • Manual intervention  – For growers who are willing to “get in there”, physical measures exist to reduce overstretching. These measures may include bending the stems, which will cause small tears in the tissue of the plant leading the stem concentrating on stem regeneration instead of vertical growth. 
  • Topping  – This is another form of manual intervention. It is designed to affect its shape, yield, and size. Topping cuts off the dominant stem and forces the plant to focus on two alternative colas instead. This puts a stop to stretching temporarily and is usually timed to the period just before flowering. Once flowering has actually begun, topping should not be carried out. 
  • Genes – Like we have already discussed, Indica plants tend to grow shorter, therefore, if you are aiming for a short plant, they would be a good bet. Similarly, you can pick a sativa strain and anticipate its stretch. This will allow you to both prepare for it, and “tame” it effectively. Searching through the websites of the seedbanks, and breeders, should give you additional information you require. 
  • Light type – Have you ever heard that that HPS (High Pressure Sodium) lights generally encourage stretching? Using HID lighting could help you combat this further stretching. You could leave your MH (Metal Halide) bulb in in the first 2-3 weeks of your plants’ flowering cycle, and then switch to a HPS bulb.
  • The same applies to CFL growers that are utilizing flowering (2700K) , and vegetative (6500K) colored bulbs. You can use your vegetative (6500K) colored bulbs for the initial 2-3 weeks of flowering then switch to your flowering(2700K) bulbs.
  • Light Distance – Monitoring how far your lights are in relation to your plants will ensure that they don’t have to overstretch to get to the lights. You can use the “hand test” to ensure you find the closest point you can place the plants near the light without harming them. 

Hand test: If you find the heat from your HPS or CFL light to be uncomfortable painful, so does your plant. You can move the lights an inch away and carry out the test again until you get to a comfortable distance. Note. This does not work for LED lights.

Other General Rules that apply to Light Distance:

  • Always maintain fluorescent and CFL lights a few inches away from your cannabis plants.
  • MH/HPS lights should be maintained at an appropriate distance depending on their size. 
  • In the case of LEDs, each model is different and the manufacturer's instructions should be followed keenly.  However, the general recommendation is keeping most LED’s 12-18″ away. The more powerful LED lights should be kept much further away. 

When a strain gets to the point where is ready to enter get into the stage where it undergoes the most drastic growth period inducing extra  stretching, the use of metal halide lamps could be used to discourage the growth of extra-long stems.

Making the Stretch Your Friend

As much as it is vital that you are prepared for the flowering stretch, it does not have to be a bad thing. If you know what to expect, you can even use it to your advantage. While extreme stretching may prove to be detrimental to your yields, this does not have to be the case. In fact, when properly factored, it can actually help you increase your harvest. Farmers who have sizable grow rooms which can sustain tall plants can actually use stretching to increase total yields with the additional vertical surface area colas can grow from. Either way, preparing in advance for the stretch will ensure you benefit, rather lose from it. 

A grow space that is taller also allows you the liberty to choose from taller sativa strains, which allows you more strain choice. Shorter strains in taller grow spaces could lead to a waste of resources and the space not being utilized optimally. Growing taller strains would allow you to efficiently harvest more in a shorter span of time. 

On the other hand, if your grow space is short, it would be wise to choose a strain that doesn’t stretch much, or for you to carefully control the stretch of your plant in cases where you do not have much choice. Measuring your plant against your grow space will give you the luxury of knowing your plants will not get uncontrollably tall, especially when you switch them to the flowering stage. 

In a nutshell, the ‘Flowering Stretch’ is another gem of knowledge that will make your journey of raining cannabis that less painful, and that much more successful. So go and factor in that “stretch”!

Sebastian is a passionate advocate of CBD's therapeutic potential, dedicating himself to exploring its diverse benefits. As a seasoned writer, he eloquently shares his insights and personal experiences with CBD, aiming to educate readers about its transformative power. His life's mission is promoting holistic wellness, with CBD at the heart of his advocacy.