- Escrito por : Ciara
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The colors of marijuana plants can vary depending on the type of crop you’re growing and the kind of climate that you’re growing it in. On more than one occasion, experienced growers wake up to find that at some point in their plants’ life cycle some strains have changed from green to purple, maybe blue and in some cases even black. Sometimes this happens simply due to the genes of each strain, like the famous Purple Haze or Blueberry; there are certain phenotypes that can go black in parts during the last few weeks of the flowering period with a minimum temperature of 18ºC and 24ºC indoors, although original Blueberry strains tend to go slightly blue and Purple Haze tends to go from lilac to dark purple, although some Panama and Colombian strains can go slightly pink.
The change in color is generally attributed to the appearance of anthocyanin, a water-soluble pigment that plants generate either due to their genes or due to potassium deficiency, and low temperatures can also influence color change. Sometimes your plants might trick you, showing colors due to nitrogen excess and you end up thinking that the color change is due to its genes; you need to make sure you’re using the right substrate and fertilizers. Nitrogen excess doesn’t just manifest itself by making your plants’ leaves darker; it also shows up in the stems and trunk, which will turn purple. Plants that change color due to genes tend to do so in the buds as well, making for some extremely attractive colorful buds. This color change isn’t adjustable, so it’s not possible to stop your plants changing color if it’s in their genes.
If it’s not in their genes, it could also be due to a lack of phosphorus which tends to come out during the flowering phase, maintaining a healthy green during the growth period and at around the fourth flowering week the leaves will begin turning purple, lilac or slightly red. Although, if you automatically assume that this is because of the temperature, then you’ll continue with your crop as if this feature was simply aesthetic, but it’s an easy mistake to make as your plants are actually giving you an important indication that they’re lacking something, and you’ll definitely notice it in the final yield of your crop. If this is the case, the coloring will sometimes be accompanied by yellowish welts on the leaves which is quite easy to fix; a few waterings with a good fertilizer rich in potassium should be able to improve your plants health, although this solution doesn’t always fix the problem completely. Sometimes the lack of potassium can be due to an excess of salts, in which case you’d need to wash your plants’ roots out and then fertilize. There are some cases in which you can find this balance of nutrients in the substrate but due to an incorrect pH level the coloring can still appear. To solve this, wash the roots and adjust the pH: remember to always water your plants with the correct pH. You’ll know the issue has been solved when your plants’ color doesn’t begin getting worse or darker, and the new leaves grow out green and healthy. This almost always happens with acidic pH levels, and basic pH levels tend to turn the leaves a slight yellow color.
Some strains can also turn purple or blueish in cold temperatures, around 10ºC; remember that cannabis plants prefer temperatures between 20 and 30 degrees, although indica strains can put up with colder temperatures than sativa strains. If you correct the temperature, your plants should go back to their original color. This phenomenon is called Ruby, and it’s the same thing that occurs in blood oranges, which need cooler temperatures to turn red. The appearance of these pigments is due to a change of DNA in just one section of the plant, known as retrotransposons.
Like we said before, these colors are due to anthocyanins, flavonoids that are naturally present in plants and can be found in the leaves, stems, branches, flowers and even in the roots. Depending on the strain and crop conditions, these flavonoids might choose to show themselves, and an acidic pH can also increase the chances of the anthocyanins being released, causing a dark purple color to appear. Their initial function is to protect the plant from UV rays as well as pathogens by changing color, thought of as a defense mechanism against predators.
It seems that anthocyanins have a series of important properties as well; anti-inflammatory, pain relief and neuro-protectant. There are some strict relationships between anthocyanins and CB1 and CB2 receptors, as well as having come to light that a diet rich in anthocyanins can improve health, including the cardiovascular system, preventing obesity etc. although in this particular case anthocyanins in cannabis don’t have any direct effects when smoked, although they might be more effective in infusions like tea.
Author: Fabio Inga
Translation: Ciara Murphy
Marijuana colors are due to the presence of anthocyanins, flavonoids that can appear due to genes, temperature changes or deficiencies.