A succulent shifting from green to a deep shade of purple often sparks concern. This transformation is a common observation, known as “stress coloring,” as the plant adjusts to external factors. The key question is whether this vibrant purple hue signals a healthy, aesthetic response or indicates harmful distress.
The Role of Anthocyanins in Succulent Color
The purple color is not a sign of sickness but the visual evidence of a biological process involving specialized pigments. While chlorophyll, the pigment responsible for green, is always present for photosynthesis, the purple, red, and blue tones are primarily attributed to a group of pigments called anthocyanins. Succulents produce these pigments as a protective mechanism. These compounds act like a natural sunscreen, filtering out intense ultraviolet (UV) radiation that could damage cellular structures. Generating a higher concentration of these pigments shields the plant from environmental stressors like high light exposure or cold temperatures.
Purple as Desirable Stress Coloring
In most cases, purple coloration is a sought-after aesthetic response, often called “sun stressing” or “cold stressing.” This desirable change is typically triggered by increased light intensity, such as moving the plant to a brighter window or outdoors. The plant remains firm and healthy, with leaves tightly packed, indicating a controlled reaction. Cooler temperatures can also prompt this change, especially when conditions are above freezing (40 to 50 degrees Fahrenheit). When the purple coloration appears gradually, and the plant maintains turgid, plump leaves, it confirms optimal care, including sufficient light and proper watering.
When Purple Signals Harmful Distress
While a gentle blush of purple is healthy, a rapid, extreme color change accompanied by physical symptoms signals harmful distress. The purple color alone is not the problem, but it becomes a warning sign when paired with tissue destruction. If the purple quickly darkens to black or deep maroon spots that feel dry and papery, it suggests severe sunburn or scorching from sudden exposure to intense, unacclimated light. A purple plant with leaves that are mushy, translucent, or leaking water indicates freeze damage or severe overwatering. Conversely, purple coupled with extreme shriveling, crispness, or a lack of turgor indicates severe drought stress.
Adjusting Care to Control Color
Managing care allows you to control the intensity of the purple coloration. If the purple hue is desirable and the plant is firm, maintain current light and water conditions to keep the color vibrant. To intensify the color, gradually increase the duration of direct sun exposure over several weeks to stimulate further anthocyanin production. If the purple signals distress, immediate corrective action is necessary to reverse the damage. For sun scorching, move the plant out of direct, intense afternoon sun to a location with bright, indirect light. If the leaves are mushy and translucent, check the roots for rot and allow the soil to dry completely before watering. To return the plant to a greener state, simply reduce the light exposure or raise the ambient temperature, which naturally decreases the production of protective purple pigments.