Tuesday, August 28, 2012

Sempervivum: Hens and Chicks

I'll be giving a talk on Hens and Chicks at the first Camellia Garden Club meeting of the season early next month and thought I'd share the information on my blog this week.

Sempervivum literally means "live forever" because they grow and propagate so readily. These succulents are called by many names (semps, hens and chicks, houseleeks), but whatever you call them, they are amazing plants.
Hens and Chicks are fun and easy to grow, yet there is enough variety to keep you entertained for a lifetime. With over 3,000 named sempervivum cultivars, these succulents are available in all colors, shapes, textures and sizes. They are suitable for rock Gardens, screes, walls, banks, container gardens and alpine houses. (Scree- Loose rock debris covering a slope. A slope of loose rock debris at the base of a steep incline or cliff.)

Hens and Chicks is a common name for a group of small succulents belonging to the flowering family Crassulaceae, native to mountainous areas of Europe and Asia They grow close to the ground with leaves formed around each other in a rosette, and propagating by offsets. The "hen" is the main plant, and the "chicks" are the offspring, which start as tiny buds on the main plant and soon sprout their own roots, taking up residence close to the mother plant.

These houseleeks grow in symmetrical rosettes of fleshy leaves up to 2 ½” in diameter with a spread of 4” upwards and form hardy ground-hugging mats. They have star shaped flowers on succulent stems and although the rosettes die after flowering they are replaced by numerous offsets.

Climate and Growing Locations
Throughout the US, Extremely Cold Hardy
Hens and Chicks are hardy and can be grown throughout the USA. Sempervivum like cool nights and need a cold-dormant season to be healthy. They prefer growing zones 4-8. In colder areas it may be beneficial to move the plants into a greenhouse or cover during them during severe winter weather. Hairy cultivars also appreciate shelter from winter rain with a piece of glass or clear, hard plastic.

Sun Preferences
Full Sun to Part Sun
Sunlight brings out bright colors in Sempervivums. When planted in full shade many varieties tend to fade to a plain green color. However, in hotter weather during the summer and in the southern United States, afternoon shade can actually help plant colors last longer.

Soil Requirements
Sandy, Excellent Drainage
Good drainage is the most important requirement for Sempervivum. Plant them in sandy soil or add compost, potting soil, gravel or vermiculite to the ground to help with drainage. Hens and Chicks survive in soil where other plants can't grow. They do great with very little soil, even in gravel and cracks in rock walls; however, accumulated water will kill the plants. Ideally the soil pH level should be neutral, between 6.6 and 7.5.

Watering Needs
Low, Drought Tolerant
Immediately after transplanting, water generously. After that let the soil dry out between watering. These succulent plants are drought resistant since they store water in their leaves, but they still need water to thrive. During the summer heat they will need to be watered more frequently. Don’t over water. If you see your plants begin to struggle, make sure the soil drainage is good and cut back on the watering.

Hen & Chick Plant Propagation
Hens and Chicks produce numerous offspring, thus allowing them to "live forever". The quantity and speed at which babies are produced depends on the variety. Sempervivum can be divided anytime during the spring/summer growing season. The baby chicks can be re-planted elsewhere or left to grow around the mother hen.
These grow babies on runners. Just pull off the chicks and plant elsewhere. It is best to remove the babies when the runner has begun to wither. Offsets root quickly and contact with soil is enough for them to start growing.
Growing from the offsets preserves the characteristics of each cultivar. Seeds taken from the Sempervivum flowers generally produce plants that are untrue to type.

Sempervivum Life and Death Cycle
Once a hen plant produces a chick, that chick will begin producing its own babies after only 1 season. Sempervivum plants generally only live for 3 years, so the plants have 2 productive years before they die. After 3 years and having produced many baby plants a Sempervivum grows a tall center stalk that blooms before the plant dies. Cutting off the center stalk will not prevent the plant from dying.
It is extremely fun to grow Hens and Chicks and watch them mature and produce offsets. Their colors change drastically throughout the season due to maturity, temperatures, sunlight exposure, and other factors. Be sure to give your plants enough space to spread. Ideally they should have 4” for small plants and 6-8” for large varieties. Adequate space produces nicely formed rosettes.

Popular varieties include: Sempervivum arachnoideum (cobweb houseleek) is a hardy succulent perennial. Evergreen, vigorous and mat-forming, with numerous small green rosettes with a fine ‘cobweb’ of white hairs joining the leaf tips. Sempervivum calcareumis an attractive species with grey-green leaves with purple tips and pink flowers. Sempervivum tectorum is a very variable species, with shades of green and brown with or without contrasting tips. It grows 2-5” tall. It has rosettes that are 1” in diameter upwards and has a spread of 4” upwards. Colorful cultivars have been bred, such as “Caramel” a delicious warm caramel color, along with reds, pinks, bronzes and greys.

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