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.
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.
RED OR PURPLE STEMS CAUSED BY GENETICS OR LIGHT
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.
Below, you’ll find a checklist of potential stressors that might be causing your plants to develop red or purple stems:
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.
Cannabis plants react to stress in unpredictable ways. It may seem odd, but sometimes discolored stems are caused by seemingly unrelated factors like overwatering, bugs, or heat. That’s why it’s important to pay close attention to plants, use good watering practices and maintain a great growing environment when cultivating cannabis.
Hot days and/or cold nights can trigger purple or reddish stems and leaves. If the discoloration appears the day after a cold night, the quick change in temperature may have caused the colorful stems. Typically temperature fluctuations cause stems to look purple, but sometimes the color can appear reddish.
A standard PH Test Kit has everything you need to test and adjust pH
Keep grow lights the recommended distance away to avoid symptoms from light stress
In this case, you probably have nothing to worry about as long as you aren’t seeing any other symptoms and plants are growing fast and healthy.