From the perspective of the Clivia plant, temperature is a fundamental environmental cue that governs every stage of its life cycle, from growth and flowering to dormancy. As a species originating from the shaded, forested regions of South Africa, its physiological processes are finely tuned to a specific thermal range. Straying too far from this range disrupts these processes, leading to stress, poor health, and a failure to thrive or bloom. The optimal temperature range can be broken down into key seasonal components that mimic its natural habitat.
During the spring and summer months, which correspond to its primary growth period, the ideal temperature range for Clivia is between 60°F and 75°F (15°C and 24°C). At these temperatures, enzymatic activity within the plant is optimized for photosynthesis, allowing for the efficient conversion of light into energy. This energy is then directed into the production of new, strap-shaped leaves and the strengthening of the plant's substantial root system. Temperatures consistently above 80°F (27°C) can induce heat stress. The plant may respond by reducing its metabolic rate to conserve water, resulting in slowed growth. The leaves can become pale, wilt, or develop scorched tips as transpiration rates outpace water uptake. Furthermore, high heat can inhibit the preliminary biochemical processes that initiate flower bud development for the following season.
Autumn is the most critical season for triggering the Clivia's spectacular bloom. To initiate flower bud formation, the plant requires a distinct period of cooler temperatures. The optimal range for this crucial stage is between 50°F and 55°F (10°C and 13°C) for a duration of approximately 6 to 8 weeks. This cool period acts as a physiological signal, informing the plant that winter is approaching and that it should prepare for reproduction. From the plant's viewpoint, this cool spell is not a hardship but an essential environmental trigger, much like the chilling requirement for fruit trees. Without this temperature cue, the plant's internal chemistry will not shift from vegetative growth to reproductive development. It will likely remain healthy and leafy but will fail to produce a flower spike in the spring.
Following the autumn cool period, the Clivia enters a state of winter rest. During this time, which should be relatively dry, the ideal temperature range is slightly warmer than the bud-initiation period but still cool, between 55°F and 60°F (13°C and 15°C). This cool rest allows the plant to conserve energy. Growth essentially halts, and the plant's metabolism slows down significantly. This dormancy is vital for the maturation of the flower bud that was initiated in the autumn. Exposing the plant to high indoor winter temperatures, such as those above 70°F (21°C) near a heater, can cause the plant to break dormancy prematurely. This can lead to weak, etiolated growth and may cause the developing flower bud to abort, a phenomenon known as "blasting," where the bud withers inside the leaf sheath without emerging.
While Clivia can tolerate brief excursions outside the ideal ranges, there are absolute limits for survival. Prolonged exposure to temperatures below 35°F (2°C) can cause severe cold damage. The water within the plant's cells can freeze, rupturing the cell walls and leading to soft, mushy leaves and irreversible damage to the root system, often resulting in death. On the opposite extreme, temperatures consistently above 90°F (32°C), especially when combined with direct sun, can cause fatal heat stress, effectively cooking the plant's tissues and leading to systemic collapse.
