Sempervivum is a genus of monocarpic succulents in the family Crassulaceae, commonly known as Houseleeks. Other common names include Live-forever and Hen and Chicks. There are about 50 species and 4,000 named cultivars.
Sempervivums are with a wide range of colors of the leaves and the size and form of the rosettes. Their natural habitats are typically 3,000 to 8,000 feet (900 to 2,500 m) above the sea level, from Morocco to Iran, through the mountains of Iberia, the Alps, Carpathians, Balkan Mountains, Turkey, the Armenian mountains, to the northeastern part of Sahara and the Caucasus.
The generic name "Sempervivum (sem-per-VEE-vum)" means "always (forever) alive." It is a compound of two Latin words, the adverb "semper," meaning "always," and "vivuvm," the neuter form of the adjective "vivus," meaning "alive," and refers to the plant's hardiness and durability.
The common name "Houseleek" refers to the growth of some species on the roofs in Europe, while "Liveforever" derives from the generic name and refers to their hardiness and durability. The common name "Hen and Chicks" comes from the appearance of the plants. The mature rosette "hen" produces offsets "chicks" around them or at the end of long stolons. As the "chicks" mature, they will also produce offsets, becoming a "hen" themselves. The common name, "Hen and Chicks," is shared with plants of other genera like Echeveria.
Sempervivums are alpine succulents with thick fleshy leaves arranged in a dense rosette. The rosettes are between 0.5 and 6 inches (1.3 and 15 cm) in diameter. Leaves are glossy or matt, sometimes with a waxy bloom or downy hairs. Some Sempervivums have hairy rosettes. The color of the leaves varies from green, yellow, orange, pink, red, to brown. Plants need to be grown in full sun to exhibit the different colors fully. The small offsets arise in a cluster around the parent rosette, forming mats of rosettes. Each rosette is monocarpic, meaning it dies after flowering, but the offsets will continue to reproduce vegetatively, allowing the plant to seem to live forever. Flowers are star-shaped, usually pink or red (although a few species have pale yellow flowers), and appear in terminal clusters.
The members of the genus Sempervivum are usually easy to recognize, although they may sometimes be confused with the members of the genus Echeveria. However, Sempervivums are often not easy to identify. Even a clone can look very different under various growth conditions or different times of the year.
In some places, Sempervivums are traditionally grown on the roofs to protect the house from fire and lightning and keep the household members safe and prosperous. It is also believed that they protect the household against witchcraft. In addition, the juice from the leaves has been used in folk remedies for centuries for their coolant, anti-inflammatory, astringent and diuretic properties.
Growing Conditions for Sempervivum
Sempervivums are among the most frost-resistant succulents, making them popular garden plants. They are an excellent choice as ground cover for rock gardens and xeriscaping but also grow very well in a range of different outdoor containers.
These succulents prefer a spot in full sun but will appreciate some afternoon shade if planted in hot climates. Sempervivums are not suitable for indoor growing because they usually do not get as much sunlight as they like. In most cases, they will first stretch towards the closest light source and then eventually die. However, grow lights can help to keep your indoor Sempervivum healthy.
To ensure Sempervivums thrive, they need a well-draining soil mix with 25 to 50 % sand, gravel, and perlite or pumice. They can also grow in regular garden soil but make sure you only water when the soil is dry. If planting in a pot, a commercial soil mix for succulents should be sufficient to keep the roots dry and happy.
Almost all Sempervivums are frost-hardy and thrive in much colder temperatures than other succulents. Therefore, they are perfect for cold climates, as they can handle temperatures down to -30 °F (-34.4 °C). Sempervivums are also heat-tolerant but prefer average summer temperatures between 65 and 75 °F (18 and 24 °C).
Choose a pot with drainage holes, wide but not too deep, so that the plant can spread easily in the space around.
General Care for Sempervivum
Sempervivums are low-maintenance plants once established, but there are some tips you can follow to make sure your plants are thriving. They will grow best if you can mimic the environmental conditions of the mountains from which they came.
Although drought-tolerant, Sempervivums require consistent moisture during the growing season. Water thoroughly during the spring and summer and allow the soil to dry out between watering. It is best to water in the early morning or evening. Never let water sit in the rosette or underneath the pot. Reduce watering in the fall when plants enter dormancy. Mature rosettes planted in the ground happily spend the winter under a blanket of snow, and they can overwinter without receiving extra water from you. Young rosettes with unestablished roots or plants in containers may need a bit of water to make it through winter.
Most Sempervivums grow well without feeding, but they benefit from a controlled-release fertilizer at the beginning of the growing season. They can also be fertilized once a week with a diluted liquid solution, such as a balanced 20-20-20 fertilizer at quarter strength. For young plants, use a fertilizer with less nitrogen. Too much nitrogen can soften the tissue and make the rosettes susceptible to rot.
Plants in containers will benefit from being repotted. Repot as needed, preferably during the spring. Make sure the soil is dry before repotting, then remove the pot and knock away the soil from the roots, removing any rotted or dead roots. Place the plant in a new pot and backfill with fresh well-draining soil. Leave the plant dry for a week, then begin to water lightly to reduce the risk of root rot.
How to Propagate Sempervivum
Sempervivums can be grown by seeds or by offsets produced each season.
The easiest way to propagate Sempervivums is by dividing the offsets. Gently lift the offsets away from the mother rosette, snip the stolon connecting the two, and plant them into well-draining soil. The best time to divide the offsets is spring or summer, once they are at least a quarter of the mother rosette's size.
Sow the seeds indoors at temperatures between 65 and 75 °F (18 and 24 °C). Fill trays or pots with well-draining soil mix, scatter the seeds, and press them into the surface of the soil. Keep moist until germination. It takes from two to seven weeks for seeds to germinate. You can start the seeds in the fall to have seedlings in size for transplanting in spring.
Pests and Diseases of Sempervivum
Sempervivums are tough plants that usually grow without problems as long as they are not overwatered.
Keep an eye out for mealybugs, aphids, scale insects, root mealybugs, and vine weevils.
Mealybugs most often bother the plants grown indoors, in greenhouses, or outside in damp weather. First, try to remove the bugs using a cotton swab dipped in rubbing alcohol. For a more serious infestation, you can use insecticidal soap or an insecticide.
Aphids seem to be attracted to plants stressed from insufficient light. Use a blast of water from a spray bottle and try to knock off as much as you can see. Let the plants dry out for a few days, and then take a spray bottle with a solution of 50/50 rubbing alcohol and water.
Scale insects are sap-feeding insects named for the shell-like waxy covering concealing their bodies. They attach themselves to the stem and underside of leaves. If caught early, scale insects can be rubbed off by hand or a cotton swab soaked in rubbing alcohol.
The root mealybugs and vine weevils are even harder to notice. The vine weevils eat leaves during spring and summer, but they can cause the most damage over fall and winter when they feed on plant roots. This damage can result in wilting and plant death. Spraying the plant with 70% rubbing alcohol may help control these pests.
It is rare to see Sempervivums suffering from bacterial, virus, or fungus infections. However, they can be susceptible to rust disease. Crown rot may also occur in wet soils. Both problems can be prevented if Sempervivums are grown in dry conditions.
Toxicity of Sempervivum
Sempervivums are not known to contain any toxic compounds. Therefore, they are considered safe plants to grow around pets and children.
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