From our perspective as Lithops, the shift in our coloration to shades of red, purple, or brown is not an immediate cry for help, but rather a sophisticated survival strategy. We originate from the harsh, sun-scorched landscapes of southern Africa, where intense ultraviolet (UV) radiation is a constant fact of life. Our primary "skin," the thick, fused leaf pair, is already adapted to handle high light levels. However, when the light intensity surpasses our optimal range, we activate a biochemical defense mechanism. We begin to produce protective pigments, primarily anthocyanins (which appear red or purple) and sometimes betalains (which can appear reddish). Think of these pigments as our internal sunscreen. They form a protective layer within our cells that absorbs excess light energy, particularly the harmful blue-green and UV wavelengths, preventing it from damaging the delicate photosynthetic machinery within our chloroplasts.
To understand why this is necessary, you must know what happens inside us. Our bodies are designed to store water and perform photosynthesis. Within our cells, we have chloroplasts containing chlorophyll, the green pigment that captures light energy to create food. When light is too intense, this energy capture system becomes overloaded. The excess energy can create reactive oxygen species, which are highly destructive molecules that can degrade proteins, lipids, and even our DNA. By producing red or brown pigments, we are effectively creating a shade cloth at a cellular level. These pigments intercept the surplus photons before they reach the chlorophyll, dissipating the energy as harmless heat. This process, called photoprotection, ensures that our photosynthetic engines are not "burned out," allowing us to continue producing energy without catastrophic internal damage.
It is crucial for you, our caretaker, to distinguish between a healthy stress response and a sign of severe distress. A gradual development of reddish or bronze tones, especially on the sides of our leaves facing the strongest light, is typically a sign of acclimation. This is our way of building up tolerance to a bright environment. We are simply putting on our sunglasses. However, if the coloration is rapid, intense, and accompanied by other symptoms, it indicates we are in distress. Look for a sunken, shriveled appearance, or a change in texture where our leaves become soft, mushy, or develop permanent white or tan, crispy patches—these are true sunburns where our tissue has been irreparably damaged and died. This often happens when we are moved too abruptly from a low-light setting to direct, intense sun without a gradual period to build up our protective pigments.
While sun stress is the most common cause of reddening, other factors can also influence our hue. The natural aging process can cause the outer leaves to turn brown and papery as we prepare to shed them for a new leaf pair—this is a normal part of our annual cycle. Furthermore, our genetics play a significant role. Some species and cultivars are naturally predisposed to exhibit grey, brown, or reddish tones even under ideal lighting conditions. It is also important to rule out other stressors. For instance, root rot caused by overwatering can sometimes manifest as a discoloration that might be mistaken for sun stress, but it will almost always be accompanied by a soft, swollen, or collapsing body. Always consider the overall condition of our body and your care routine when diagnosing the cause of our color change.
