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How to Control Cannabis Vertical and Lateral Growth

Cannabis vertical growth

Big, bushy cannabis plants indicate a bountiful crop. However, height alone does not imply a large yield. However, it may mean the reverse. Recognizing when a cannabis plant is stretching and understanding what to do about it are critical for producing high yields.

An overview of stretching cannabis plants

Stretchy, spindly plants may be a nuisance for various reasons. Plants with uncontrolled growth are undesirable, from falling over to burning themselves on your lighting system. A higher plant may not always provide a larger crop. Tall cannabis plants can indicate unhappiness, mainly if they do not receive enough light. In addition to causing your plants to expand, a lack of light will reduce the size and quality of your eventual yield. So, how can you keep cannabis plants from becoming overgrown? Several solutions are available, some of which will help you enhance your production!

Importance of preventing your cannabis plants from stretching

  1. Security and privacy: Large cannabis plants will draw more attention due to their size.
  2. Flowering stretch: During the early flowering period, certain plants might double in size. If you do not plan ahead, you will find that you don’t have enough area in your growing space.
  3. Even light distribution: Taller cannabis plants will receive a lot of light in the canopy but very little near the ground. This implies that the bottom buds will develop slowly, lowering your production potential.
  4. Provide light to smaller plants: Some strains will be smaller than others if you are cultivating many strains. Unless you limit the height of the higher ones, the smaller plants will not get enough light.
  5. Prevent light burn: Your cannabis plants will burn if they grow too tall and go too near to the lights. This can slow overall development and damage the primary colas at the top.

Reasons why your cannabis plants stretch

Improper light distance

If your lighting is too far away from your plants, they will stretch to come closer. This is a normal behavior resulting from seeking to outgrow competing plant life.

Red-dominant light spectrum

During the spring and summer, cannabis plants develop. Plants are exposed to blue and white light spectrums during these periods of peak sunshine. The sunlight diminishes and reaches the red range throughout fall. Choose the appropriate light spectrum for the growth stage to provide your plants with enough photo-fuel.

Insufficient lighting

If your lights aren’t powerful enough, your plants will reach for them no matter how high or low they’re placed—they’ll seek light until they find it.


Some cannabis strains, such as landrace Sativa seeds, like to grow tall and spindly. While they may be regulated, if your height is severely limited, many Indica seeds are preferable.

You’ve kept them vegging for far too long

Cannabis plants grown at the photoperiod stage will continue to grow.

Vegging cannabis plant

So, if you veg them for too long and don’t keep them under control, they will grow enormous and unmanageable.

How to prevent your cannabis plants from stretching

Pick suitable genetics

Some strains stretch more than others, and the Indica/Sativa distinction isn’t adequate to forecast a plant’s stretching ability. However, all hope is not gone. Growing stable seeds with predictable outcomes is possible if you get your cannabis seeds from a credible cannabis seed bank. Additionally, the seed bank will generally note any unusual behavior linked with a good or negative strain that the grower should be aware of.

Maximize light intensity (without burning your cannabis plants)

This method is convenient, but you must exercise caution to prevent harming your plants in other ways. Because your cannabis will naturally reach toward the light, minimizing the distance between the canopy and the light source will result in less stretching. Once again, this is a delicate balancing act. Different distances between your lamp and the canopy are recommended depending on the kind of light. Keep your plants at the lower end of this spectrum to maximize sun exposure without scorching them or slowing their growth.

Enhance air circulation

Despite the occasionally turbulent factors, most cannabis plants remain erect and rooted in the soil when growing cannabis outdoors. A gentle breeze works wonders for the interior section of the stem, generating microscopic cracks that gradually increase its thickness and stiffness. In this manner, if you experience rapid growth in a matter of hours, your plants should be able to cope. This wind will also help to restrict vertical growth.

Additionally, you won’t need expensive equipment to establish proper air circulation in the grow room. A primary standing fan will serve if you’re planting a handful of plants. Set to oscillate and watch your stems strengthen over the next few weeks.

Maintain ideal temperature levels

Temperatures above 29°C are problematic for stretching; heat causes stems to become spindly and weak, and it can induce stretching on its own or worsen an existing problem. This is why, in addition to maintaining appropriate grow room temperatures, you must ensure that hot lights are not burning your plants. However, moving your lighting too close to your plants will not assist your stretching problem. A thermo-hygrometer is always useful to have on hand so you can constantly check the environmental parameters of your grow area. Cannabis flourishes at various temperatures during its life cycle, so keep the temperature within the optimal range.

Reduce nutrition and CO₂ supplementation

If you want to keep stretching to a minimum, it comes to reason that decreasing the substances that drive your plants’ development might be beneficial. Nutrient cannabis schedule and CO₂ lead to enhanced growth; thus, reducing these factors during early bloom may keep stretching in control. Also, limiting your plants’ essential resources, such as water and nutrients, will not improve their health or development; it’s all about establishing a balance between supplying enough and offering too much. Furthermore, while this should not be your primary line of defense against stretching, it is an alternative to explore.

Enable proper spacing between your cannabis plants

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

Shorten the vegetation phase

Shortening the veg period of your Feminized or Autoflower plant is one definite approach to avoid excessive vertical growth. In fact, by growing in a SOG (several little plants in one grow room), you’ll practically start blooming right away, restricting how much the plants may potentially develop. If you want your plant to grow before blossoming, monitor the moment at which its present height, once doubled, is sufficient for your needs. If you don’t want your plants to grow taller than two meters, flip them to bloom before they reach a meter, just in case they decide to increase their height.

Alternate the flowering light spectrums

Light is the most crucial environmental factor influencing a plant’s susceptibility to stretch. Furthermore, specific lighting encourages greater stretching than others. Consider a standard HID lighting system. Metal halide (MH), which generates blue light, is typically used to stimulate vegetative development before converting to red high-pressure sodium (HPS) for blooming.

Flowering marijuana plant

Plants are considerably more likely to stretch significantly after switching to HPS, as this shift in light communicates the natural changing of the seasons. Try applying MH during the first few weeks of bloom to avoid stretching. The blue light it generates will keep internodes short while not impeding development too much. This way, you may continue to benefit from HPS’s bud-boosting red light spectrum afterward.

Training your plants

If your plants aren’t responding to your calls to stop stretching, or if you’re about to embark on a significant blooming stretch, some extra hands-on care may be required. Training and pruning enable you to shape your plant by reducing vertical growth and controlling development. Simple LST may be utilized to promote lateral development and adequate light exposure, or you can take it a step further with a ScrOG, an advanced type of LST. As your plant progresses from late vegetative to early bloom, you may route its branches through a mesh screen to optimize bud development while encouraging nearly entirely lateral growth.

Considerations for tall cannabis plants grown indoors

There are two essential things to watch out for when plants grow tall indoors.


Cannabis emits a significant amount of water. Cannabis loves relative humidity (RH) levels between 50 and 65%. When they grow too large, humidity can become an issue since the plants continually emit water vapor into the air. Water then collects on the grow room’s leaves and other surfaces, potentially producing mildew and other problems. If humidity becomes an issue, a dehumidifier or raising the power of the exhaust fan can assist. Defoliating can also help to manage humidity by increasing ventilation. Remove just the lowest and mid-level fan leaves. This also helps to increase light penetration to the lower blooming branches.


As with humidity, when cannabis plants grow too large, the temperature in the grow-op might rise. Reduced ventilation and excessive height can raise temperatures and place plants too near to grow lights. Cannabis grows best at temperatures averaging 25°C. Plants are more prone to stretch when temperatures are above this level. High temperatures can also impact leaf and flower production.

Picture of Ed Rushford

Ed Rushford

Ed Rushford’s impact on cannabis growing is undeniable. Though he tends to focus primarily on 2 areas, plant training techniques and dealing with disease, pests, and other problems, he has offered many insights into how cannabis plants live and grow. That’s not to say that Ed is unfamiliar with the complete life cycle of cannabis, from seed to harvest, but he uses his widespread knowledge to hone in on the minutia and niche areas of growing cannabis. Ed’s goal is to spread knowledge and allow for everyone to become better growers. About this Author

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