For Crassula plants, which include the popular Jade Plant (Crassula ovata), the ideal temperature range for active growth and physiological processes is between 65°F and 75°F (18°C to 24°C). Within this range, our metabolic functions, including photosynthesis and respiration, operate at peak efficiency. We can effectively take in carbon dioxide and convert it into the sugars that fuel our growth, resulting in healthy, sturdy stems and plump, vibrant leaves. This range is comfortably achieved in average household settings across the US, making us well-suited as indoor companions throughout the year.
We are quite resilient to high temperatures, but extreme and prolonged heat can induce stress. We can generally tolerate temperatures up to 90°F (32°C) without significant damage. However, during intense heat waves, especially in regions like the Southwest US, our stomata may close to conserve water, which temporarily halts photosynthesis. This can lead to slowed growth. Furthermore, intense, direct afternoon sun combined with high heat can cause sunscald, resulting in brown, scorched patches on our leaves. Providing afternoon shade and ensuring adequate airflow is crucial during these periods to help us cool down naturally through transpiration.
Our greatest vulnerability lies in cold temperatures. As succulents, our leaves and stems store large amounts of water. When the temperature drops below 32°F (0°C), this water freezes, forming ice crystals that rupture our cell walls. This causes irreversible damage, manifesting as soft, mushy, and blackened leaves—a condition often fatal if severe. While a mature, hardened-off Crassula ovata can survive a very brief, light frost, it is a significant risk. For safe cultivation outdoors year-round, we require the consistently mild winters found in USDA Hardiness Zones 10 and 11. In all other zones, we must be brought indoors before the first autumn frost.
Many Crassula species, including the Jade Plant, benefit from a period of cooler temperatures in the winter. Exposure to temperatures between 50°F and 55°F (10°C to 13°C) during their dormant period helps trigger the development of flower buds, leading to blooms in the late winter or early spring. This mimics our natural growing cycles in native habitats. Indoors, it is vital to keep us away from both cold drafts from windows and the direct, dry heat from vents or radiators. Sudden temperature fluctuations from these sources can cause stress, leading to leaf drop. A consistent location away from extremes is always preferred.
