The cobweb succulent, Sempervivum arachnoideum, is a distinctive plant known for its unique appearance. Its most striking feature is the delicate, web-like hairs that stretch across its rosettes, giving it the common name “cobweb” succulent. This characteristic makes it a popular choice for succulent enthusiasts and gardeners, adding intriguing texture to any collection or landscape.
Identifying Features
The cobweb succulent, Sempervivum arachnoideum, is recognized by the fine, silvery-white hairs that densely cover the tips of its leaves and span across the rosettes, resembling a spider’s web. These “cobwebs” are a natural protective feature, shielding the plant from intense sunlight and reducing moisture loss. The rosettes are compact, ranging from 1 to 3 inches (2.5 to 7.5 cm) in diameter, and grow in a mat-forming habit.
The leaves display colors from vibrant green to reddish hues, often intensifying when exposed to cooler temperatures or ample sunlight. As a Sempervivum, it shares the “hen and chicks” growth pattern, where a larger mother rosette (“hen”) produces smaller offsets (“chicks”) on horizontal stems. These offsets form new plants around the parent. The plant remains low, under 3 inches, but can spread up to 12 inches wide, creating a dense, carpet-like effect.
Cobweb Succulent Care
Light Requirements
Cobweb succulents thrive in bright light, preferring full sun to partial shade. Placing them in a location that receives at least 4 to 6 hours of direct sunlight daily promotes compact growth and vibrant leaf coloration. While they tolerate some direct sun, especially morning light, intense midday sun in hot climates may cause scorching, so afternoon shade can be beneficial. Insufficient light leads to etiolation, where the plant stretches and becomes leggy as it searches for more light.
Watering
These succulents are adapted to arid conditions and have low water needs. The “soak and dry” method is ideal for watering: allow the soil to dry out completely between waterings before thoroughly saturating the soil until water drains from the bottom of the pot. Overwatering is a common pitfall and can quickly lead to root rot. Watering frequency should be adjusted seasonally, every 1-2 weeks during the active growing season in spring and summer, and significantly reduced during the dormant winter months, sometimes requiring no water at all.
Soil and Drainage
Proper soil and drainage are essential for the health of cobweb succulents. They require a well-draining, gritty soil mix to prevent waterlogging and root rot. A cactus or succulent potting mix is suitable, or you can create your own by amending regular potting soil with materials like perlite, coarse sand, or pumice to enhance drainage. Ensuring pots have adequate drainage holes is also essential, as porous materials like terracotta or ceramic can further aid in drying out the soil more quickly.
Temperature and Humidity
Cobweb succulents are hardy and tolerate a wide range of temperatures, thriving in temperate to cool climates. They are cold-hardy, withstanding freezing temperatures down to approximately 20°F (-6.7°C) and surviving outdoors year-round in USDA Hardiness Zones 5a to 8b. During summer, average temperatures between 65-75°F (18-24°C) are well-suited for their growth. They prefer dry conditions with good airflow, as high humidity can increase the risk of rot and disease.
Fertilizing
Cobweb succulents have modest fertilizer needs and can thrive without additional feeding. If you choose to fertilize, do so sparingly, once every 2-3 months during the active growing season in spring and summer. Use a balanced, water-soluble fertilizer diluted to half-strength or a specialized succulent fertilizer. Avoid fertilizing during winter dormancy, as this can weaken the plant or cause root burn.
Propagating Cobweb Succulents
Propagating cobweb succulents is straightforward, primarily done through the offsets they readily produce. These small rosettes, often called “chicks,” grow around the base of the larger mother plant (“hen”). To propagate, gently separate these offsets from the parent plant, ensuring each offset has some roots attached if possible. If the offset has no roots, allow the cut end to callous over for a day or two before planting.
Once calloused, plant the offset in a well-draining succulent potting mix in its own container. New offsets may require slightly more moisture than mature plants initially, so lightly mist the soil every few days until roots establish. After the plant is rooted and established, reduce watering frequency to that of a mature plant. Propagation by seed is also possible, though less common and more challenging for the home gardener.
Common Problems and Troubleshooting
Cobweb succulents are robust, but issues can arise from improper care. Root rot is a common problem, resulting from overwatering or inadequate drainage. Signs include mushy stems or leaves, and the plant may appear to wilt despite being watered. To address this, ensure the plant is in well-draining soil and a pot with drainage holes, and adjust your watering schedule to allow the soil to dry completely between sessions.
Pest infestations, while less frequent, can occur. Mealybugs are a concern, appearing as small, white, cottony masses on the plant, often nestled in leaf crevices. If detected, isolate the affected plant immediately to prevent spread. A common solution involves dabbing the pests directly with a cotton swab dipped in 70% isopropyl alcohol, which dissolves their protective coating. Leggy growth, characterized by stretched-out stems and widely spaced leaves, indicates insufficient light. Moving the plant to a brighter location with more direct sunlight will help it maintain a compact, desirable form.