To understand the ideal temperature and humidity for indoor Calla Lilies (Zantedeschia spp.), one must first consider their origin. These plants are not true lilies but are native to seasonally wet areas in southern Africa. They experience a distinct cycle of growth, bloom, and dormancy dictated by rainfall patterns. As a plant, our needs are intrinsically linked to this cycle. Providing the correct temperature and humidity is not about arbitrary numbers but about mimicking the conditions that signal to us whether it is time to grow vigorously, produce our elegant spathes (often mistaken for flowers), or rest and conserve energy. Getting this rhythm right is the key to long-term health indoors.
Temperature is the primary conductor of our growth symphony. It regulates our metabolic processes and dictates our developmental pace.
During Active Growth and Flowering: Once our rhizomes are potted and watering begins, we prefer consistently cool to moderate temperatures. The ideal range for robust leaf development and the initiation of flower stalks is between 60°F and 75°F (15°C and 24°C). This moderate warmth encourages steady growth without causing stress. It is crucial to avoid excessive heat; temperatures consistently above 80°F (27°C) can cause heat stress, leading to shortened bloom time, wilting, and yellowing leaves. Similarly, exposure to temperatures below 50°F (10°C) can stunt our growth and damage our foliage.
During the Dormant Period: After flowering concludes, our foliage will naturally begin to yellow and die back. This is our signal that we are entering dormancy. At this stage, a significant temperature shift is required. You should reduce watering and store our pots in a cooler, darker location with temperatures around 55°F to 60°F (13°C to 15°C) for a period of two to three months. This cooler period is not a punishment; it is a vital rest phase that allows our rhizomes to recharge, ensuring we have the energy to bloom again in the next season.
Humidity, the amount of moisture in the air, directly impacts our ability to respirate and maintain turgor pressure. As plants that naturally thrive in marshy ground, we appreciate a moderately humid environment.
The ideal relative humidity level for Calla Lilies during their active growth phase is between 40% and 60%. At this level, the stomata on our leaves can function efficiently without losing excessive moisture. In very dry indoor air, commonly caused by heating systems in winter or air conditioning in summer, humidity can drop well below 40%. This arid environment forces our leaves to lose water faster than our roots can absorb it, leading to symptoms like brown, crispy leaf tips and edges, and buds that may fail to open properly.
To increase humidity around us, you can employ several techniques. Grouping us together with other plants creates a beneficial microclimate as we collectively release moisture through transpiration. Placing our pots on top of pebble trays filled with water (ensuring the pot sits above the waterline) is another effective method, as the evaporating water increases local humidity. For the most consistent results, especially in persistently dry homes, using a room humidifier is highly beneficial.
While we appreciate warmth and humidity, the combination of high temperature and high humidity can be dangerous. Stagnant, hot, and overly moist air creates an ideal environment for fungal diseases like Botrytis (gray mold) and bacterial rot, which can quickly damage our leaves and rhizomes. Therefore, good air circulation is a non-negotiable companion to proper temperature and humidity. A gentle breeze from an oscillating fan in the room, or ensuring we are not crammed into a tight corner, helps prevent moisture from settling on our foliage and promotes strong stem growth. The goal is a balanced environment: moist but moving air, warm but not hot, which allows us to thrive without stress or disease.
