National collection of Diaschias
 

I see in another thread that Chris Boulby is the "curator" of the national
collection of Diaschias.

I have a question, which is applicable not only to that collection, but to
all collections of plants whose hardiness is somewhat on the iffy side:

Do you have to take cuttings annually of every variety in the collection in
order to be insured against winter losses, or is the collection kept under
glass? (Or both?)

Franz