Marijuana plant stretch during bloom phase is a problem for most cannabis growers, especially if you’re growing in a grow tent or other space with limited vertical height.
Plant stretch refers to the fact that cannabis plants put on a lot of height during the first half of bloom phase.
A plant that starts bloom phase 30 inches tall might be 65 inches tall or taller at the end of bloom phase.
Some of this stretch is useful because it contains developed buds, but 40-50% of it is wasted vertical growth with longer-than-needed space between internodes.
Some marijuana growers combat plant stretch by poisoning themselves and their plants using plant growth regulator products such as General Hydroponics Bush Load.
Other plant growth regulator products are Gravity, Flower Dragon, and Bushmaster.
These products contain dangerous chemicals such as paclobutrazol (PACLO) that shouldn’t be used on crops ingested by humans.
You can control marijuana plant stretch using non-poisonous techniques and materials.
- Plant scientists working for hydroponics nutrients company Advanced Nutrients report that marijuana plants engage in most of their stretch during the first three hours after the grow room lights go on.
During this time three-hour time period starting when your lights go on, lower your grow room temperature 4-5 degrees BELOW your crop’s nighttime temperature.
Do this for the first 3-4 weeks of bloom phase.
- Be warned that a common hydroponics grow room temperature control technique for increasing resin production and encouraging earlier maturation causes marijuana plant stretch.
This technique adjusts nighttime bloom phase grow room temperatures to be 5-9 degrees cooler than daytime temperatures.
Unfortunately, this technique creates marijuana plant stretch when used during the first 3-4 weeks of bloom phase.
You reduce marijuana plant stretch by reducing the difference in grow room temperature between night and day to 3-4 degrees during the first 3-4 weeks of bloom phase.
If for example if your lights-on temperatures are 75°F, you’d want your lights-off temperatures to be 71°F.
After the first 3-4 weeks of bloom phase, you go back to having a 5-8 degree lower temp during lights-off as compared to lights-on.
This promotes ripening and resin production.
- Add lighting that provides a more full-spectrum set of wavelengths.
Marijuana plant stretch comes in part from poor lighting.
This includes low light intensity that is often found when growers are using inferior LED, CFL, or other types of lighting that can’t match the intensity of quality LED and high intensity discharge (HID) lighting.
On the other hand, your grow room might have enough light intensity, but it might not have enough breadth of light wavelengths.
Using the standard bloom phase HPS (high pressure sodium) lighting, your plants are missing out on blue, ultraviolet, and some infrared spectrum.
This creates cannabis plant stretch.
Consider adding Lush LED lighting and/or metal halide such as Hortilux Blue to expand the light spectrum your plants are getting.
- Use the right hydroponics nutrients.
One brand of hydroponics nutrients (Advanced Nutrients) is designed by a famous marijuana grower who understands that marijuana plant stretch isn’t what you want.
He created hydroponics base nutrients containing natural rather than poisonous substances so plant stretch is discouraged without use of dangerous PACLO.
The Connoisseur pH Perfect hydroponics base nutrients contain the highest percentage of safe stretch-reducing substances of any base nutrients on the market.
You also use Bud Ignitor, designed to limit plant stretch while encouraging early flowering and more budding sites.
The Advanced Nutrients bloom phase hydroponics base nutrients and supplements program also limits plant stretch because the brand creator knows how to balance ratios of nutrients elements.
In most other feed programs, there’s way too much nitrogen and phosphorus, and/or there are defective pH buffers.
This contributes to marijuana plant stretch.
- Another technique is to top your plants just as they go into bloom phase.
The effect is that the plant stretch is shortened and channeled into dense growth that goes horizontal rather than vertical.
If you see plant stretching, and especially if you have long bloom phase plants, you could top again at two weeks into bloom phase.
- Finally, know that Sativa genetics tend to stretch more than hybrid, Kush, Indica, and Afghanica.
If you have limited vertical space, you don’t want to grow pure Sativa or Sativa-dominant strains (for example, a strain described by the breeder as 70-30 Sativa-dominant).
Marijuana plant stretch wastes space, electricity, yield potential, nutrients, water, and time.
Shorter, stockier, denser cannabis plants are easier to manage, require less trellising and other supports, and yield better.
Now you have ways to decrease plant stretch without resorting to poisonous products!