How to delete btrfs subvolume?

I have a snapshot that I'd like to delete:

04:03:21::mlissner@pounamu::~ 
↪ sudo btrfs subvolume list /
ID 257 gen 267078 top level 5 path @badroot
ID 258 gen 267151 top level 5 path @home
ID 422 gen 267151 top level 5 path @

The one called @badroot is bad and must go. But:

04:03:23::mlissner@pounamu::~ 
↪ sudo btrfs subvolume delete \@badroot
ERROR: error accessing '@badroot'
04:03:31::mlissner@pounamu::~ 

So I don't know where to proceed. I tried reading the help file:

↪ sudo btrfs subvolume delete --help
usage: btrfs subvolume delete <subvolume> [<subvolume>...]

    Delete subvolume(s)

But that's useless too. Perhaps the kind people of the Internet have ideas.