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Cannabis Purple Stems

cannabis purple stems

Table of Contents

Causes of purple stems on your cannabis

What do purple stems mean? Purple stems may indicate that your plants will grow slowly and that buds will form slowly and be smaller and less developed. Purple stems, stalks, and petioles may indicate a problem with the nutrients for cannabis, root zone pH, plant health, or grow room environment issues.

Genetics

When cannabis purple stems are caused by genetics, the plant will operate and seem healthy otherwise. To put it another way, if the plant is not showing any other signs of distress, the pigmentation could be a part of its genetic makeup. There are numerous cannabis genetics available, and many of these varieties can produce purple or red pigmentation.

Temperature

After extreme temperature changes, purple stems yellow leaves may appear. Due to the abrupt temperature change, a cannabis plant grown outside with a day temperature (80°F) and a nighttime temperature (50°F) may produce red or purple stems. Suppose an indoor gardener notices purple stems cannabis due to temperature variations. In that case, they may need to control the temperature of the dark cycle so that it is no more than 10-15 degrees cooler than the lights-on cycle. Temperature fluctuations in an indoor garden can eventually lead to more severe humidity problems.

Pathogens

Fungi like Fusarium and Botrytis can change the color of your plants’ stems and foliage. Fusarium attacks seedling stems, eventually causing them to topple over or “damp off.” Occasionally, it can cause stems to appear dark brown, red, or slightly purple. Conversely, Botrytis affects larger plants, causing them to die by robbing them of nutrients. Fusarium and Botrytis can spread from plant to plant and should be treated as soon as possible.

Light intensity

Another reason for cannabis purple stems is the intensity of the light. When intense light is directly subjected to your plants, they may have purple stems in veg. If the cause is a lack of light intensity, the stems lower on the plant will usually appear greener. Coloration under severe light is a natural plant defense mechanism protecting the plant from UV light.

Purple cannabis plant
Purple cannabis plant grown indoors

Indoor gardeners who use LEDs or lighting systems with a high UV output are more likely to encounter this occurrence.


Find out the perfect light cycle for cannabis to ensure there are no lighting


Stress

Cannabis plants respond to stress in a variety of ways. Discolored stems may indicate transplant shock, heat stress, overwatering, or bug infestation. As a result, if you notice purple stems, you must pinpoint the source of the discoloration. Here is a list of potential stressors that may be causing your cannabis red stems:

  • Temperature or humidity problems: If the temperature or humidity levels in your grow room feel off, this could contribute to purple stems on cannabis plants. If you suspect that temperature and humidity are stressing your plant, make the necessary adjustments.
  • Cannabis pests: Certain cannabis strains are more susceptible to pests and plagues than others. You must act quickly if your plants have discolored stems, damaged foliage, stunted growth, and signs of mildew, gnats, or spiders.
  • Light or heat pressure: Keeping a grow light close to the plants can also cause red stems. Regardless of the weather! Some strains are more susceptible to stress than others, but almost all plants have a maximum light level. A plant can be stressed by light intensity even if the temperature is cool, just as a snowboarder can get sunburned in the cold. Because too much light can cause red stems and other stress symptoms, it’s always a good idea to keep your grow lights at the manufacturer’s recommended distance. LED grow lights, in particular, are notorious for causing light-burn in plants if kept too close.

Nutrients deficiency

Deficiencies in nutrients cause various symptoms, including yellowing or drying new and old foliage and purple stems on fan leaves. Red and purple stems, followed by brown, dried-out leaves, are early signs of phosphorus deficiency. Conversely, magnesium deficiency causes red stems on fan leaves. Remember, those nutrient deficiencies cause more than discolored stems; they also cause stunted growth, damaged foliage, and other symptoms.


Use our guide on cannabis deficiencies to identify the type of deficiency affecting your plants and correct it as soon as possible.


pH

It is critical to get the pH of your soil and nutrient solution just right for healthy plants. Unfortunately, it is also a problem for most growers. Cannabis prefers slightly acidic soil (we recommend keeping it at 6.5 for best results). Your plants may lose healthy foliage and develop nutrient deficiencies if your soil is either too acidic or too alkaline, as they struggle to absorb nutrients from your fertilizers. Check your pH levels if your plants have red or purple stems or other signs of a nutrient problem. We suggest investing in pH and conductivity testers to get a clear picture of your soil’s pH. These devices deliver precise readings of your soil pH and the electrical conductivity of your nutrients, allowing you to see how well your plants absorb the fertilizer.

Solutions to cannabis red stems

  1. Once you’ve determined that pH issues cause the purple stems, here’s what you should do. First, start preparing your nutrient solution. Check the pH of the nutrient solution with pH drops or a digital pH pen; it should be between 6.0-7.0 when growing in soil and 5.5-6.5 when growing in hydro and coco coir. When the pH is very high or too low, modify it with any pH Up or pH Down and verify it again until it is within the ideal range. If you’re still having issues, the problem is in the substrate, so flush for a few days and then constantly feed, usually with the pH’d nutrient solution.
  2. If you have nutrient deficiencies (phosphorous and magnesium), use slow-release nutrients or grow in super soil, which has all the nutrients your plants require from seed to harvest. Ensure to feed your plant immediately, or look for fertilizers containing both phosphorus and magnesium to avoid this.
  3. Light intensity – If your plants are displaying red stems but aren’t entirely healthy, dim the light fixture or change the height and keep an eye on how they develop. If the problem persists, keep changing the height of your light until your plants thrive.

Cannabis stems turning purple aren’t essentially a reason for worry. If your plants start developing discolored stems, keep a close eye on them and look for other signs that the discoloration isn’t caused by genetics or light exposure.

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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. While Ed has a particular penchant for the SCROG, Schwazzing and Mainlining techniques in his own garden, he has basically mastered every growing technique which has allowed him to choose the ones he personally favors. When it comes to pests and diseases, Ed draws on his own experiences as a novice grower way back in the day and builds upon his own learning curves to provide comprehensive guidance on dealing with plant problems in a pinch.
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. While Ed has a particular penchant for the SCROG, Schwazzing and Mainlining techniques in his own garden, he has basically mastered every growing technique which has allowed him to choose the ones he personally favors. When it comes to pests and diseases, Ed draws on his own experiences as a novice grower way back in the day and builds upon his own learning curves to provide comprehensive guidance on dealing with plant problems in a pinch.

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