All really big lumps that dry right through successfully get put aside for these large vases. They won’t take water as I’ve tried everything and there is no treatment that will fully waterproof wood. However you can’t have fresh flowers all year round and just imagine one of these with a display of rushes and grasses.
To help with the presentation I taper the hole to control the spread. Additionally this leaves extra weight in the base lowering the center of gravity and allowing a taller display.