Succulents store water in fleshy leaves, stems, or roots, making them popular for their unique appearance and low maintenance needs. Whether they can remain outdoors during the winter depends entirely on their genetic tolerance and the local climate. Succulents are broadly categorized into two groups, requiring different approaches to winter care. Overwintering success requires understanding this distinction and managing environmental conditions.
The Critical Distinction: Tender Versus Hardy Varieties
Succulents are separated into tender and hardy varieties based on their origin. Tender succulents, also known as soft succulents, originate in warm, frost-free climates and have no tolerance for freezing temperatures. These plants, including Echeveria, Crassula (Jade Plant), and Aeonium, face damage when temperatures dip below 40°F and will not survive a hard freeze at 32°F.
Hardy varieties evolved in mountainous or alpine regions and are prepared for prolonged cold and snow. Examples include Sempervivum (Hens and Chicks) and many species of Sedum (Stonecrop), which can survive temperatures down to -20°F or even -40°F in well-drained conditions. Gardeners must identify their plant’s hardiness zone rating and compare it to the USDA Hardiness Zone map for their location to determine if the plant can remain outdoors year-round. This zone indicates the average lowest winter temperature for a region, providing a baseline for survival.
Environmental Threats Beyond Freezing Temperatures
While tender varieties are threatened by frost, hardy succulents face risks beyond cold, primarily related to moisture management. The greatest threat is persistent moisture combined with cold temperatures, which rapidly leads to root and crown rot. This occurs because cold, damp soil prevents water from evaporating or being utilized by the plant, which is often dormant and not actively absorbing moisture.
Strong winter winds cause desiccation. When the ground is frozen, roots cannot draw up water, but the wind strips moisture from the leaves, leading to severe dehydration and “scorched” foliage. Ice accumulation, especially repeated cycles of freezing and thawing, can also physically damage fleshy leaves, causing cell walls to burst and resulting in mushy, discolored foliage.
Preparing Tender Succulents for Indoor Dormancy
Tender succulents must be moved indoors before the first expected frost, ideally when nighttime temperatures consistently fall to the low 40s. Before the move, plants should be “hardened off” by gradually acclimating them to lower light and humidity over two to three weeks. This is done by placing them in a sheltered outdoor spot, such as under a covered porch, for progressively longer periods before the final transition.
Once inside, these plants enter winter dormancy, slowing their metabolism. The ideal indoor setting is a cool, dry location with temperatures maintained between 50°F and 60°F, which encourages rest without risking frost damage. Watering must be drastically reduced, often to once every four to six weeks, only after the soil has dried completely. Supplemental grow lights may be necessary for six to eight hours a day, particularly in north-facing rooms, to prevent the plants from stretching due to insufficient light.
Active Protection for Outdoor Hardy Varieties
Hardy succulents left outside require specific interventions to manage excess moisture and buffer extreme cold. Improving drainage is paramount, especially for container-grown plants, which should be planted in a gritty mix containing 60–80% inorganic material like pumice or coarse gravel. For in-ground plantings, creating a slight mound or berm helps shed rain and prevent water from pooling around the crown.
Applying a thick layer of inorganic mulch, such as pea gravel, crushed lava rock, or decomposed granite, is effective. This top-dressing prevents the leaves from sitting in wet soil, reducing the risk of crown rot during thaw periods. During severe or prolonged cold snaps, temporary physical covers can provide insulation. A cold frame, burlap, or a cardboard box placed over the plants at night offers enough protection to ensure survival.