Green is the main colour in cannabis plants. But why do we find some cannabis varieties with purple or other shades?
Three factors influence this change in shade, giving rise to plants with deep purple flowers, for example. These factors are genetics, temperature and plant nutrients.
Cannabis Genetics: Purple Varieties
The colour of cannabis is largely subject to the genetics of the plant. That is, there are varieties that are genetically predisposed to high levels of anthocyanins. Anthocyanins (from the Greek anthos: flower + kyáneos: blue) are water-soluble pigment molecules found in the vacuoles of plant cells that give red, purple or blue colour to leaves, flowers and fruits.
We could say that the colour of the different varieties of cannabis is produced by anthocyanins and the mixture of other pigments, such as flavonoids. The latter would be yellow and their function would be to attract pollinating insects.
Anthocyanins are present in all plants. But why does cannabis produce anthocyanins and flavonoids? The answer is for protection. That is, these pigments act as a sunscreen to protect cells from ultraviolet light and to deter predators attracted to green plants.
The temperature and pH of cannabis
Another factor influencing the colour of cannabis is the temperature and the ripening of the plant (flowering). As is known, chlorophyll is the dominant green pigment in plants and often makes it difficult for anthocyanins to appear and thus prevent the explosion of colour.
So how does it go from green to purple?
With the drop in temperature and the cold days (below 10°C) the cannabis plant starts to convert chlorophyll into sugars. The sugars are absorbed by the plant as energy to produce flowers, cannabinoids and seeds. This process allows anthocyanin to break through and show the explosion of colour. Some growers intentionally let plants chill for the last two weeks before harvest. With this technique they sacrifice a little bit of the fattening of the inflorescences, but on the contrary they get an increase of resin due to the stress and at the same time they favour the change of colours.
The pigments become more pronounced as the cannabis plants mature. That is, the plant produces less chlorophyll from the dominant pigment and we begin to see those anthocyanins emerge in a show of purples, reds and blues.
The colour that anthocyanins cause in plants is closely related to pH levels. When the levels are above 7 (alkaline or basic) the plant shows bluish tones; if it is between 5 and 7 (neutral conditions) the plants offer purple colours; if the acidity level goes below 5 the plants will look reddish.On the contrary, plants with a low level of anthocyanin can produce a different range of colours in the last weeks of flowering, due to another family of molecules called carotenoids. These are responsible for the golden and yellow tones in the flowers.
How nutrients influence the colour of cannabis
Nutrient deficiencies can also influence our plant to turn purple. Thus, a deficiency of nitrogen or phosphorus causes an increase in anthocyanins and the stems of the leaves to turn purple. A sulphur deficiency can cause the stems to contain purple spots.
If during the growth phase the colour of the cannabis becomes more colourful, this is not due to anthocyanins. We are probably dealing with a lack or excess of nutrients.
Purple Kush. Now in a Non-Autoflowering version
If you are a fan of purple genetics, Purple Kush from Buddha Seeds is the strain you were looking for. Now available in a Non-Autoflowering version.
Explosive growth, Purple Kush Non Autoflowering culminates with a burst of colour in the flowering phase in just 60 days. From the first week you can see the intense purple colour of the leaves. It can culminate, depending on environmental conditions, with a genuine colour range of bright colours for its abundant resin. Ideal for making your own extracts (dry/ice).
Other varieties that can surprise you with beautiful colours in flowering are Deimos, which can become reddish or Magnum whose leaves can take on a blackish colour.