Weed turns purple primarily due to the presence of pigments called anthocyanins, which are water-soluble flavonoids that can appear red, blue, or purple depending on the pH level of the plant. Genetics determine whether a cannabis strain can produce these anthocyanins. Environmental factors such as cooler temperatures, light exposure (especially UV light), and nutrient availability can enhance anthocyanin production and promote the purple coloration by reducing chlorophyll, the green pigment in plants. Thus, the purple color is a combination of genetic predisposition and environmental conditions affecting anthocyanin expression in the plant.
Role of Anthocyanins and Genetics
Anthocyanins are the key pigments responsible for the purple color in cannabis. These pigments are also found in other fruits and vegetables like blueberries, plums, and eggplants. The specific color—red, blue, or purple—depends on the pH within the plant tissues. Some cannabis strains, such as Granddaddy Purple or Purple Haze, have genetics that naturally produce high levels of anthocyanins, resulting in their characteristic purple hues.
Influence of Environmental Factors
- Temperature: Cooler temperatures, especially below about 50°F (10°C), reduce chlorophyll production, allowing anthocyanins to become more visible, turning parts of the plant purple.
- Light: UV and blue light exposure can stimulate anthocyanin production, enhancing the purple color in both outdoor and indoor-grown plants.
- Nutrient Levels and pH: Proper pH balance and nutrient availability, particularly phosphorus, affect the plant's health and can indirectly influence the appearance of purple colors by affecting anthocyanin levels.
Color and Potency
The purple coloration does not imply the cannabis is stronger or more potent. Potency depends on cannabinoid and terpene profiles, which are not directly related to the color imparted by anthocyanins.
