What an incredibly interesting subject this is, and what useful information, especially to one just about to start filling and planting some new troughs, with built up crevices. I don't fully understand all you have written Zdenek, but will re-read it all several times and hope to absorb more. Thanks for starting this thread and I hope many more Forumists with geological minds will contribute.
As always, the photographs are wonderful and I am sure now that I'll plant one of my two Daphne petraea plants in the crevices. Many thanks.
Regarding daphne petraea in crevices, I have to say that in my garden plants on own roots do not flower very much. Surprisingly they flower very well in pots in alpine house together with dionysias. I use almost the same sterile substrate as for dionysias and almost do not fertilise them (just my lack of control). As pots are buried in wet sand, roots are spread there and plants they have always enough water, especially in summer time, as it influence next year flowering. Different story is daphne cneorum pygmea, flowering well in crevice, even in nature they always grow in grass. I think it is the beauty of crevice mystery. I add couple of crevice plants.
