Sempervivum marmoreum

Sempervivum marmoreum, Balkan Houseleek, is native to southeastern Europe in a geographical area spanning the Balkans, Bulgaria, Romania and Greece and western Ukraine with the type species locality being Mount Athos in Greece. It is diploid (2n=34) with pink or reddish flowers. It is sometimes found in garden centres under the deprecated synonym of Sempervivum schlehanii. It is a very variable species particularly in the colouration of the foliage and the degree of indumentum on the foliage with some variants being almost entirely glabrous with very few cilia and other variants being densely pubescent. Even at the type locality of Mount Athos there is variability with glabrous forms with ciliate margins being found at higher altitudes and more pubescent morphotypes found at lower altitudes. Most subspecies have now been redefined within the original species. Plants from the Rila Mountains in Bulgaria are a densely pubescent variant with short, velvety hairs on the foliage and were previously described as Sempervivum erythraeum or Sempervivum marmoreum subsp. erythraeum. However, another subspecies, Sempervivum marmoreum subsp matricum - found further north in the border regions of Hungary and Slovakia - has now been described as a separate species, Sempervivum matricum and has a different ploidy being tetraploid (2n = 68).

Sempervivum marmoreum is a gem. The plants offered here are close in morphology to the Mt. Athos lectotype from higher altitudes: a densely-rosetted glabrous form with fine ciliate margins, freely offsetting and with a tough I-will-survive attitude. So much more desirable than all those dubious cultivars with an unknowable parentage that you find in garden centres.