What Is the Temperature Tolerance of a Succulent?

Succulents are known for their resilience, but they possess specific temperature tolerances that influence their health. Understanding these thermal limits is necessary for proper care, ensuring the plants thrive indoors or in an outdoor landscape.

Ideal Temperature Range for Succulents

Most succulents flourish within a temperature range of 60°F to 80°F (15°C to 27°C). This window represents the optimal conditions for their active growing season, allowing them to produce new leaves, stems, and roots. Within this moderate thermal zone, the plants’ metabolic processes, including photosynthesis and water uptake, function most efficiently.

When temperatures move consistently outside this range, many succulents enter dormancy. This is a survival mechanism where growth slows or stops to conserve energy. During dormancy, prompted by either cold or intense heat, a succulent’s need for water diminishes significantly, which is an important factor in year-round care.

Understanding Succulent Cold Hardiness

A primary distinction in succulent care is their ability to withstand cold. Succulents are categorized as either “hardy” or “soft,” defining their tolerance for freezing temperatures. Hardy types, like many Sempervivum and stonecrop Sedums, originate from mountainous regions and can survive deep freezes, some enduring temperatures well below 0°F (-18°C).

Soft succulents, including Echeveria, Aeonium, and Crassula, must be protected from frost. When exposed to temperatures at or below 32°F (0°C), the water in their leaves freezes. The resulting ice crystals expand and rupture the cell walls, leading to irreversible damage. This injury results in a mushy, collapsed appearance from which the tissue cannot recover.

To prevent frost damage, move soft succulents indoors or to a protected location like a garage before the first freeze. In areas with only occasional light frosts, covering plants overnight with a frost cloth can provide enough insulation. Placing them in sheltered areas, such as near a south-facing wall or under an overhang, also offers a warmer microclimate.

Managing Succulents in High Heat

Extreme heat is also detrimental to succulents. Temperatures consistently above 90°F (32°C) can induce heat stress and summer dormancy to conserve water. The most direct danger is sunburn, which occurs when leaves are exposed to intense ultraviolet (UV) radiation. High temperatures worsen this by accelerating water loss and making the plant more vulnerable.

Sunburn appears as permanent pale, white, or brown patches on the leaves that cannot photosynthesize or regain their color. To prevent this, position succulents where they receive morning sun but are shielded from the intense afternoon sun. This is important for plants in containers, as their soil can heat up much faster than the ground and scald the roots.

Protection can involve strategic placement or physical barriers. Move potted succulents to the east side of a building or under a larger tree for natural shade. For plants in fixed locations, a shade cloth can be draped over them to diffuse light and lower the leaf surface temperature. Good air circulation also helps dissipate heat.

Recognizing Signs of Temperature Stress

Identifying the signs of temperature stress allows for timely intervention, as the symptoms for cold and heat damage are distinct. Recognizing these cues helps separate temperature issues from other problems, such as improper watering.

Cold stress in soft succulents appears after exposure to freezing conditions. The most telling sign is the development of soft, mushy, or translucent spots on the leaves. In severe cases, affected leaves may turn dark brown or black, and the plant may drop leaves suddenly in response to the shock.

Heat stress presents a different set of indicators. A primary symptom is sunburn, which was described in the previous section. Leaves may also look shriveled or wrinkled as the plant loses moisture too quickly. To conserve water, some succulents will curl their leaves inward or drop them, even if the soil is moist.

How to Acclimate Succulents

Sudden changes in temperature and light can shock a succulent, leading to stress, sunburn, or cold damage. To prevent this, plants should be acclimated, or “hardened off,” when moving between environments, like from indoors to outdoors. This process involves gradually introducing the plant to new conditions, allowing it to adjust safely.

The acclimation process should be slow. Start by placing the succulent in a sheltered, shaded location for only one or two hours per day. Over one to two weeks, gradually increase the amount of time the plant spends outside. This slow exposure allows the leaves to adapt to more intense sunlight and fluctuating outdoor temperatures.