Ice plants are popular ground covers, known for their vibrant blooms and succulent foliage. Understanding their temperature tolerance is important for successful growth and longevity across various climates. These resilient plants can thrive when their specific needs are met.
Defining Ice Plants and Their Diversity
The common name “ice plant” refers to a broad group of succulent plants, primarily within the Aizoaceae family. Key genera include Delosperma (hardy ice plants) and Lampranthus (trailing ice plants). While their leaves share a shimmering, ice-like appearance, their temperature tolerances vary significantly among species and cultivars.
For example, Delosperma species like Delosperma cooperi are often hardy in USDA Zones 5-11, with some varieties such as ‘Fire Spinner’ tolerating Zone 5. Lampranthus species, including Lampranthus aurantiacus, are less cold-tolerant, generally suited for USDA Zones 9-11. This variation highlights the importance of selecting the correct species for your climate.
Cold Hardiness of Ice Plants
Ice plants, especially Delosperma varieties, exhibit a range of cold hardiness, thriving in USDA Hardiness Zones 5 through 9. This means certain varieties can endure winter lows from -20°F (Zone 5) to 30°F (Zone 9). Understanding these zone ratings is crucial for selecting the appropriate ice plant for your local climate.
When temperatures drop below freezing, plant cells can freeze, causing ice crystals to rupture cell walls. This often results in mushy, blackened, or distorted foliage, indicating frost damage. While top growth may die back in cold, wet winters, many varieties can resprout from their roots in spring, particularly if the ground remains relatively dry. Good drainage during winter is important for survival, as wet, cold conditions are detrimental.
Specific cultivars like ‘Fire Spinner’ can tolerate temperatures as low as -20°F. However, prolonged exposure to freezing temperatures, especially in wet conditions, can still cause significant damage or plant loss. Allowing ice plants to dry out and “harden off” in the fall by reducing irrigation helps them prepare for winter cold.
Heat Tolerance and Drought Resistance
Most ice plants are well-suited to hot, sunny environments due to their succulent nature. They require ample sunlight to thrive and produce their characteristic vibrant blooms. Their fleshy leaves store water, allowing them to endure prolonged dry conditions. This water storage capacity contributes to their high tolerance for full sun and makes them resilient in arid or drought-prone regions.
Ice plants thrive in temperatures well above 75°F (24°C). However, extreme heat combined with insufficient water can lead to stress. Signs of heat stress include wilting, browning or scorching of leaf edges, and a general lack of vigor. While highly drought-tolerant once established, consistent hydration during extended dry spells supports their health and vibrant blooming.
Protecting Your Ice Plants from Temperature Extremes
Protecting ice plants from cold extremes involves several strategies. For varieties in colder zones, applying a layer of gravel or pine needles as mulch around the base insulates roots and improves drainage, preventing rot during wet winters. In areas with heavy snow or freezing rain, covering plants temporarily with frost blankets or sheets shields the foliage. Container-grown ice plants are more vulnerable to cold and should be moved to a sheltered, frost-free location or indoors during freezing temperatures.
To mitigate heat stress, especially for newly established plants, proper watering is important. While drought-tolerant, ice plants benefit from deep, infrequent watering during prolonged dry and hot periods. Good air circulation also helps prevent issues from humidity combined with high temperatures. Providing temporary shade with shade cloth during intense heat waves can prevent leaf scorch, particularly in very exposed sites.
Recognizing and Addressing Temperature Stress
Visual cues indicate temperature stress. In cold conditions, leaves may appear mushy, blackened, or distorted, with dieback of stems and foliage. If roots remain viable, the plant often resprouts in spring.
For heat stress, signs include wilting, scorched or browned leaf edges, and stunted growth. To help a stressed plant recover, prune away any dead or severely damaged foliage after the extreme temperatures have passed. Adjusting watering practices, such as providing deep watering after a dry, hot spell, aids recovery. Avoid fertilizing immediately, as this can stress an already weakened plant.