The majority of popular houseplants are tropical and struggle when indoor temperatures drop below 65°F. This challenges enthusiasts with poorly heated spaces or those who intentionally keep homes cooler to save energy. However, a select group of resilient greenery possesses the necessary adaptations to thrive in cool indoor environments, typically ranging from 45°F to 65°F. Finding these cold-tolerant plants allows for maintaining a vibrant indoor garden even when the thermostat is turned down.
Understanding Plant Adaptations to Cooler Indoor Air
Plants respond to cooler air by significantly reducing their metabolic rate, slowing down all growth processes to conserve energy. Temperatures between 41°F and 50°F (5°C and 10°C) are often considered the biological “zero point” for growth, as most cell production ceases below this range.
A major concern is chilling injury, damage that occurs above freezing, typically below 50°F (10°C) for tropical species. This injury affects cell membranes, disrupting function and causing irreversible harm. Low temperatures also reduce the roots’ ability to absorb water, leading to water stress even if the soil is moist.
The efficiency of transpiration, where plants release moisture, decreases in cooler air and lower light, further reducing water uptake. Cold-adapted plants accumulate solutes like sugars within their cells to regulate osmotic potential. This mechanism helps manage water movement, prevent dehydration, and maintain cellular integrity under cold stress.
Low-Maintenance Plants for Moderately Cool Spaces
Many common houseplants manage in moderately cool conditions (55°F to 65°F), especially with cooler nighttime drops. The Cast Iron Plant (Aspidistra elatior) is durable, thriving in temperatures as low as 50°F and tolerating various lighting conditions. This perennial’s resilience suits rooms that remain relatively cool year-round.
The Snake Plant (Sansevieria trifasciata) is another excellent choice, tolerating minimum temperatures around 50°F, provided the soil is kept dry. English Ivy (Hedera helix) also prefers cooler environments, with an ideal range between 50°F and 70°F.
Cyclamen is a flowering plant that prefers cool rooms, performing best between 50°F and 65°F. Its ability to bloom is compromised by high indoor heat. The ZZ Plant (Zamioculcas zamiifolia) can tolerate a minimum of 50°F, though it is happier above 60°F.
Extremely Hardy Varieties for Unheated Rooms
For true cold room conditions (45°F to 55°F), plants that benefit from a cold period are required. The Christmas Cactus (Schlumbergera) requires a cool period, ideally 55°F to 65°F, combined with long nights to set flower buds. This response is necessary for successful winter blooming.
Dormant Citrus trees can be successfully overwintered indoors in a cool space, typically between 40°F and 55°F, staying above freezing. This cool rest period is beneficial for their overall health and subsequent fruit production. Japanese Aralia (Fatsia japonica) handles temperatures down to the 40s and 50s well.
Certain varieties of Rosemary (Salvia rosmarinus) are cold-tolerant. They can be kept indoors in a cool, bright area during winter, tolerating temperatures near 45°F. The Norfolk Island Pine (Araucaria heterophylla) is another resilient option that prefers a cooler room and can tolerate temperatures in the 50s.
Essential Care Adjustments When Temperatures Drop
The most significant change in caring for any plant in a cold room involves a drastic reduction in watering frequency. Because the plant’s metabolism slows and water evaporation is reduced, the soil takes much longer to dry out. Overwatering is the most common cause of death, as cold, wet soil suffocates the roots and invites rot.
Owners should completely suspend fertilization from late fall to early spring. Plants are not actively growing and cannot utilize the nutrients during this time. Excess fertilizer can build up as harmful salts in the soil, potentially burning the roots. Resume feeding only when the plant shows clear signs of new spring growth.
Managing light and drafts is also important to prevent sudden temperature shock, which can cause leaf drop. Even if the room is cold, plants should be kept away from leaky windows or exterior doors that emit blasts of cold air. Positioning plants to receive the best available light is still necessary to support their minimal metabolic needs.