Plant of the day is: Semperivum arachnoideum or cobweb houseleek
Well plant folks, it's Spring break and the weather is turning warm here in Saint Louis. Looking forward to getting back into the plants when the semester ends in mid May. In the meantime, enjoy a fantastic plant I really want at home.
Taxonomy, etc: The genus contains about 40 species and a whole lotta synonyms. Sepmervivum means "always living" in reference to its wintergreen leaves and it's propensity for surviving in harsh climates. Commonly called the houseleeks or frequenlty hen and chicks. Sempervivum arachnoideum L. 1753. Ever notice that letter behind a species? The 'L.' indicates that Linnaeus is attributed as the author/namer for the species. What a guy. Previously listed as Linn.
Description: They are succulent perennials that form mats of leaves in rosettes. The rosettes tend to be monocarpic which means they die after they flower, the plant forms offsets (a form of clonal reproduction) that then continue to grow until flower. The rosettes usually take a few years to form flowers. Flowers are hermaphroditic BUT the male stamens develop first and curve away from the carpels at the center to deter self pollination. A fantastic morphological tactic for controlling it's pollination no?! THIS particular species earns its name from the web like threads that form between the leaves in the rosette. The flower is NOTHING to scoff at either, rising out from the rosettes with bright pink flowers and an almost scale like scape. Glad I found a botanical description describing at as a scape. I didn't want that to 'e'scape me. Bad, I know.
Habitat/range: This particular species is one of 3 that are widely distributed throughout Europe. In particular, S. arachnoideum is found in the Apennines of Italy (take me there...someone, anyone) and much of the rest of central Europe. Fun fact: Romania is home to the largest stand of virgin forests in all of Europe (excluding Russia) mostly in the Southern Carpathians. Someone can also feel free to take me there as well. I'll gladly get lost in those woods.
Culture/care: Listed as zone 4-8 but I've also found that it is not particularly fond of wet winters (like many alpines really). Good drainage or a trough/container is crucial for success. It is typically found on siliceous soils on "soil" that is very poorly weathered. I use the term soil loosely because its mostly rock. They are very drought tolerant and should not be over-watered. Full sun for these. Many propagation protocols call for 10C temps for germination but 20-23C temps seem to be pretty effective as well. If propagating from seed I recommend a mix of about 50% fine peat with 50% "play sand" ...somewhere between fine and coarse. Use the cleanest sand you can obtain. You can germinate this in a near 100% peat mix but as with many alpines, the peat mixture tends to hold too much moisture and can damage the seedlings. If you do germinate in a higher peat mix be ready to transplant (carefully!) the small seedlings into a better drained mix. When plants are larger make sure to top dress with some kind of rock/grit if growing in pots/containers.
I'd be a fool if I didn't point you here. Some work by Dr. Giuseppe http://www.photomazza.com/?Sempervivum-arachnoideum
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