To understand the ideal temperature for Lithops, one must first consider their origins. These plants are native to the arid, rocky deserts of southern Africa, primarily South Africa and Namibia. In this harsh environment, they have evolved to thrive under extreme conditions characterized by intense daytime heat followed by significantly cooler nights. This daily temperature fluctuation is not merely a condition they endure; it is a fundamental driver of their growth cycle and metabolic processes. Their entire physiology, from their water-storing succulent leaves to their shallow root system, is fine-tuned to this specific thermal rhythm. Therefore, replicating this pattern indoors is the key to their health and encourages them to flower.
During their primary growth periods in spring and autumn, Lithops require warm days and cooler nights to mimic their natural cycle. The ideal daytime temperature range for active growth is between **70°F and 80°F (21°C and 27°C)**. This warmth facilitates photosynthesis, allowing the plant to produce energy. Crucially, they benefit from a noticeable drop in temperature at night. Ideal nighttime temperatures should fall between **50°F and 60°F (10°C and 15°C)**. This diurnal swing of roughly 20°F (10°C) is vital as it helps reduce respiratory water loss during the cooler, darker night hours, conserving precious moisture. It also signals to the plant that it is in a favorable season for growth.
Lithops enter a state of dormancy during the peak of summer heat, a survival tactic to avoid excessive water loss. During this period, which typically aligns with the hottest months, they require protection from intense heat. While they can tolerate high temperatures, sustained heat above **90°F (32°C)** can cause stress, sunburn, or even cook the plant if it is in a small pot against a hot window. Proper ventilation is critical to prevent heat buildup. If temperatures consistently exceed this upper limit, providing slight afternoon shade or moving the plant slightly away from the most intense sun exposure can prevent damage. The goal is not to keep them cold but to avoid lethal overheating.
In winter, Lithops are largely dormant and preparing for their flowering season or the development of new leaves. During this rest period, they require cool and completely dry conditions. The most critical factor is avoiding any combination of cold and dampness, which will rapidly lead to rot and death. While they can tolerate cool temperatures down to approximately **40°F (4.5°C)** for short periods if the soil is bone dry, this is the absolute minimum. For safe overwintering, it is advisable to keep them in a cool, bright location with temperatures consistently above **50°F (10°C)**. They must receive no water during this cool dormancy to remain healthy.
Achieving these ranges indoors involves mindful placement. A south or east-facing windowsill is often ideal, providing ample light and warmth during the day. At night, the temperature near a window naturally drops, helping to create the desired daily fluctuation. Be cautious of microclimates: a plant touching a cold windowpane in winter might fall below the safe minimum, while one sealed inside a terrarium or on a shelf with poor airflow can easily overheat in summer. Using a simple thermometer near your plants will help you monitor their conditions accurately, allowing you to adjust their position with the changing seasons to maintain their ideal temperature range.
