Grass root masks: Grow roots into life-casting moulds?

My face casing is next week, and I'm still semi-sub-consciously thinking of things I can do with it. I was thinking of the woven grass structures I want to experiment with in the summer (trying to create people or buildings and then photographing their slow decay and return to nature). I was wondering if grass can be 'moulded'. I'm not sure as any attempt to search for 'grass' and 'mould' just returns stuff about lawn treatments for mildew ;) BUT it's definitely possible to grow grass roots into moulds. The process seems to use wheatgrass rather than native grass so it wouldn't be suitable for the idea above, since I intended to leave the art in public spaces as well as private ones, and I wouldn't want the wheatgrass to take hold. However, it could be suitable for an experiment in the garden I guess. I could also be a lot of fun!