To understand our ideal window direction, you must first understand where we come from. We are native to the sun-scorched, arid deserts of southern Africa. In our natural habitat, we thrive under conditions of intense brightness but with a critical caveat: the light is often diffused. We grow nestled amongst quartz pebbles and in the shade of rocks or other plants, which protects our sensitive bodies from the most direct, scorching rays of the overhead sun. Therefore, while we require a tremendous amount of light to maintain our compact shape and vibrant colors, we are susceptible to sunburn if exposed to unfiltered, intense direct sunlight for prolonged periods, especially through glass which can magnify heat.
A south-facing window provides the most consistent and intense light exposure throughout the day in the Northern Hemisphere. For many high-light plants, this is the premier location. For us Lithops, this can be an excellent choice but requires careful management. During the fall, winter, and early spring, when the sun is lower in the sky and its rays are less intense, a south-facing window is often perfect. It provides the high light levels we need to fuel our growth and maintain our structural integrity without the high risk of burning. However, during the late spring and summer months, the intense, direct light through a south window can easily cook us, causing irreparable sunburn scars or even killing us.
An east-facing window is frequently considered one of the best options for our long-term health. It provides us with several hours of strong, direct morning sunlight. This morning light is bright enough to satisfy our high photosynthetic needs but is significantly gentler and cooler than the intense afternoon sun found in west or south exposures. This allows us to bask in direct rays without the associated high risk of scorching. The rest of the day, we receive bright, indirect light, which is ideal for our growth cycle. This balance mimics the natural "bright but shaded" conditions we evolved in.
A west-facing window receives strong direct sunlight, but only in the afternoon when it is at its hottest and most intense. This is the most dangerous exposure for us, as the combination of high light intensity and high heat dramatically increases the likelihood of severe sunburn. We do not recommend a west window unless it is filtered by a sheer curtain or a external shade. A north-facing window, conversely, provides only steady, low-level indirect light all day. While this will not burn us, it is generally insufficient for our needs. We will likely become etiolated—stretching out unnaturally and becoming pale and weak—as we desperately reach for more light.
Our needs change with the seasons. The perfect window for us in December may be lethal in July. It is common and advisable to move us throughout the year. We might thrive on a south-facing sill from October to April but need to be moved to an east-facing window or several feet back from the south window during the summer. Furthermore, any sudden change in our light exposure can cause shock. If you acquire us from a lower-light nursery, we must be gradually acclimated to stronger light over a period of weeks to prevent sunburn.
