On part of the Allotment (500' and exposed to easterlies) I have a patch 5 x
6 of 30 dahlias. In the past, every November, I have lifted and dried and
stored them in the loft.

2 probs with this method - some of the tubers cover a large area and I don't
like splitting them. Leaving the tubers uncovered for the Winter is out of
the question. I've lost established fruit trees and a 5 year old Wisteria,
in recent Winters.

Main prob, my back isn't so good these days. I'm aware that porous membranes
are good. However, I have some black heavy tarp which covers the area
perfectly. Question : Would the lack of water penetration for say, 3 months,
be detrimental to the tubers?