cannabis stem problems

Should You Worry About Purple Or Red Cannabis Stems?

Finding red or purple stems on your cannabis plants might freak you out, but it’s not necessarily a cause for concern. Keep reading for an overview of the potential causes of red or purple cannabis stems.

Red or purple stems in cannabis can be a sign of stress, nutrient deficiency, pathogens, or simply genetics. Keep reading to learn when to be concerned about red stems, and when not to.


You might be alarmed the first time you spot red or purple stems on your cannabis plants. But you don’t always need to be. There are countless strains of cannabis on the planet, and some of them are capable of developing incredible pigmentation.

Purple strains with very dark foliage, for example, often develop purple stems too, especially if you grow them in slightly cooler temperatures. As long as your plants look otherwise healthy, there’s usually no reason to worry.

Other than genetics, another major cause behind discoloured stems is strong light exposure. If you use training methods like LST or defoliation, you may notice the exposed stems of your plants turning red, pink, or purple over time. This is completely normal and shouldn’t be cause for concern as long as your lights are sufficiently distanced and your plants look otherwise healthy.


Unfortunately, red or purple stems in cannabis can also be a sign of stress. When this is the case, your plants will usually experience some other symptoms that can help you narrow down the root cause of the problem.


Some fungi, such as Fusarium or Botrytis, can affect the colour of your plants’ stems and foliage. Fusarium affects seedlings, attacking their stems and eventually causing them to topple over or “damp off”. It can sometimes make stems appear dark brown, red, or slightly purple. Botrytis, on the other hand, affects larger plants and forms a characteristic brown line along the affected stems and branches, robbing them of nutrients and causing them to die.

Both Fusarium and Botrytis can spread from one plant to another and should be taken care of as soon as possible. Check out our previous posts on Fusarium and cannabis moulds for more information on how to deal with these deadly pathogens.


Nutrient deficiencies cause a wide range of symptoms, including yellowing/drying new and old foliage, and discoloured stems and leaves. In particular, some of the early signs of a phosphorous deficiency include red and purple stems, followed by brown, dried out leaves. Magnesium deficiencies, on the other hand, tend to cause petioles (the stalks attaching a leaf to a stem) to turn red.

If you’re worried your plants might be dealing with a nutrient deficiency, check out this post for pictures, descriptions, and easy-to-follow steps on how to identify and cure every cannabis nutrient deficiency.

Remember, nutrient deficiencies don’t just cause discoloured stems; they also cause signs of stunted growth, damaged foliage, and more. Make sure to identify the type of deficiency affecting your plants using our guide and rectify it as soon as possible.


Getting the pH of your soil and nutrient solution right is essential for healthy plants. Unfortunately, it’s also something a lot of growers struggle with.

Cannabis likes slightly acidic soil (we recommend keeping it at 6.5 for best results). If your soil is either too acidic or too alkaline, your plants can lose healthy foliage and develop nutrient deficiencies as they struggle to uptake nutrients from your fertilisers. If your plants have red or purple stems and other signs of a nutrient issue, make sure to check your pH levels.

For a clear picture of the pH of your soil, we recommend investing in pH and conductivity testers. These tools provide accurate readings of your soil pH as well as the electrical conductivity of your nutrients, meaning you’ll be able to see just how well your plants are absorbing their fertiliser.


Abrupt changes in temperature can often cause changes in pigmentation in cannabis plants. Cool nighttime temperatures in particular can lead your plants to develop dark red or purple foliage and stems. This is even more common in purple strains; in fact, growers often expose purple strains to cooler nighttime temperatures on purpose to really highlight the purple gene.

If your plants turn red or purple after a particularly cold night, pay close attention to them over the following days. If they continue to grow normally, then there’s nothing to worry about. If, however, you notice slowed growth or other signs of stress, bring up the temperature in your grow room (or consider moving your plants indoors if you’re outdoors).


Cannabis plants react to stress in myriad ways. Sometimes, discoloured stems can be a sign of transplant shock, heat stress, overwatering, or even a bug infestation. That’s why, if you spot purple or red stems, it’s important you pay close attention to identify the root cause of the discolouration.

Below, you’ll find a checklist of potential stressors that might be causing your plants to develop red or purple stems:

Root shock: Transplanting comes as a big shock to the root system. If your plants develop red or purple stems after being transplanted, a good dose of TLC should help them recover quickly.

Pests or plagues: Some cannabis strains are more prone to pests and plagues than others. If your plants have discoloured stems and also suffer from damaged foliage, stunted growth, and signs of mildew, gnats, or spiders, you’ll need to act quickly. Check out this post on common cannabis ailments for more info on how to spot and treat common cannabis pests.

Temperature or humidity issues: If the temperature or humidity levels in your grow room feel off, that may be part of your problem. Adjust temperature/humidity if you suspect they could be stressing your plant.

Light/heat stress: While cannabis loves warm weather and plenty of sun, too much heat or light can damage it. If your cannabis plants develop burnt or yellow foliage, bleaching, or curled leaves a few days after you first notice their discoloured stems, they might be dealing with light or heat stress. Be quick to address these issues, as they can have a devastating effect on your plants and greatly reduce the size and quality of your yield.


As we saw earlier, red or purple cannabis stems aren’t necessarily a cause for concern. If your plants suddenly develop discoloured stems, remember to monitor them closely and look out for other symptoms that the discolouration isn’t caused by genetics or light exposure. Also, visit the growing section of our blog for more detailed articles on how to grow cannabis, deal with nutrient deficiencies, pests, heat stress, and more.

Seeing red or purple stems on your cannabis plants? Don't freak. Click here for a detailed overview of the causes behind purple or red cannabis stems.

How To Fix Broken And Bent Cannabis Stems

Although broken, bent, and detached stems might seem like devastating problems, they can be easily fixed using simple methods. By using tape to re-attach or tighten stems, and by using support structures to upright bent stems, disaster can be swiftly evaded. Ignoring these problems, however, could lead to an unhealthy plant and a smaller yield.

Broken, bent, or detached stems are common growing problems, especially for first-time growers. They have the potential to seriously endanger your grow and limit your final yield. However, with care and attention, these issues can be fixed quite easily. Even branches that have completely snapped off the plant can be saved by using a few simple methods.


Stems can be damaged by something as simple as moving plants carelessly. This can especially be a problem with plants that are more rigid and upright. Moreover, damage from wind or excess airflow can similarly damage branches and stems.

Stems and branches can also be broken or bent from the utilisation of growing techniques like low-stress and high-stress training methods. Techniques that bend or otherwise stress branches inherently have the potential to lead to stem complications. Even if branches don’t split or break completely, the damage caused by bending them too much can harm plant vigour and production.

It is important to treat broken or otherwise damaged stems quickly. Open wounds can lead to infections in the plant, similar to humans. These kinds of breaks and open wounds will not only lead to a lower yield, but have the potential to kill the plant altogether.


The three most common types of stem damage are broken or split stems, bent or folded stems, and detached stems.


When training rigid plants, or when training during the flowering phase, plants are at an added risk for broken stems. If left untreated, the branches of these stems will stop growing. These stems can be easily fixed with the tape method or with a support structure. Plants have a natural healing mechanism that will allow them to mend themselves. However, if you act quick enough, you may not even notice a reduction in the plant’s production on these branches.


This is the most common type of stem damage that occurs. When branches are bent or stressed too much by training techniques, permanent damage can occur. Bent or folded stems are unable to support themselves. Bends or folds can make it more difficult for branches to receive water and nutrients from the plant. These stems will continue to grow, but at a slower pace than the rest of the plant. This is not just because they are bent, but because their bending makes them hang lower, potentially blocking their exposure to light.


Branches that have completely snapped off and detached themselves from the plant can be one of the most stressful problems to deal with. Luckily, these detached stems can be healed and mended with the same techniques used for other kinds of stem damage. They simply require more care and attention than bent or broken stems. However, if the detached stem is small, or located towards the bottom of the plant, it may be best to simply toss it away and cut your losses.


The most common method of fixing broken stems is to use the tape method. Both duct tape and scotch tape can be used to help plants heal. Which kind you use will depend on the extent of the damage and the weight of the branch being mended.

Follow these steps to fix your broken stems:

  1. Prepare a piece of tape about 10cm in length (you may need more for larger stems/branches).
  2. Wrap the tape around the broken stem, making sure it fully covers its original base.
  3. Ensure that the stem and its base are packed together tightly to allow mending.
  4. Leave the tape on for between 2–4 weeks.
  5. Check healing progress every day.

Tip: Be sure to wrap the tape around the branch as tightly as possible. Packing everything together will greatly assist the healing process. When removing the tape, take care so as to not damage the stem again. Sometimes the stem may still be fragile or may not have fully healed. In these situations, it is easy to retear the stem unintentionally.


Bent stems can be fixed with support structures. Follow these steps to fix a bent stem:

  1. Place a thin bit of wood or plastic in the soil, directing it upwards toward the bent stem.
  2. Attach the stem to the support structure with a piece of duct tape.
  3. Leave the support structure in place until the stem is able to stand upright on its own.
  4. Remove the tape and support structure carefully.

Similarly to fixing broken or detached stems, be very careful when removing the tape. Bent stems can be easily damaged again if not careful.


The main way to protect your plants from stem damage is to be careful when handling them, especially when moving your plants, or when utilising training techniques that stress stems or branches. When training your plants and bending your branches, be careful not to overdo it. Plants with rigid stems and structures are especially susceptible to damage. Although it can be easily fixed, it is best to take proper care so as to avoid an issue in the first place.

It is advisable to take proper precautions to protect your plants from excessive wind or airflow damage. Moving air can provide numerous benefits for cannabis plants, including making the stems stronger. However, too much of it can cause significant structural damage, affecting health and yield in kind. In strong enough winds, plants can be toppled over or completely uprooted.

Reinforcing and protecting plants against the wind is simple and inexpensive. It is usually inadvisable to rigidly secure cannabis as this will completely prevent motion. It is much better to keep your plants next to some form of windbreaker. Rows of hedges or trees can act as natural defences. Meanwhile, fences and walls can act as man-made barriers. Bamboo matting, shade cloth, and plastic film can also make for suitable windbreakers. Some growers also prefer to use mesh fences that surround the plants. These fences can then be layered with cloth or plastic to ensure they act as effective barriers.

Broken, bent, or detached stems are some of the most common problems that growers face. These issues can easily be fixed with some tape and structural support.