Reading various catalogs, one gets the distinct impression that a variety of coveted plants can only be grown on tufa, or troughs as a less desirable alternative.
I'm thinking about a mountain side with relatively decayed stone on surface with progressively more solid stone as one goes deeper. Cracks and fissures may be only a few mm wide, but may extend many meters deep and wide.
So what is the magic of troughs? It might be in part a totally prepared soil mix somewhat disconnected from the earth? Or might it be the extra TLC that is likely to be extended to troughs or crevice gardens?
Right now I am having success with Penstemons and other westerners in a sand bed, but I keep evolving my idea of mix; right now I'm using coarse sand, with stone dust and pebbles and a pebble mulch in areas.
Now I have a few Townsendias to plant out, guess they'll have to love it or leave.
I've been fantasizing about getting a few 10 wheelers of limestone dumped in a berm, with mine run below and finer stones on top and then throwing on some coarse sand and stone dust mix to fill cracks and fill depressions. (Tufa would be nice but unrealistic.) It seems it would be an interesting experiment, but perhaps a spectacular folly.
Any thoughts, anyone?
Best for the gardening season,
Charles Swanson
NE Massachusetts USA Z6 40+ inches rain (snow and ice)