maildir - whats the skinny?

[Harry Putnam <reader@newsguy.com>]

There is precious little in gnus info about using maildir.  Under
mail-sources section it is described a bit how to collect from one.

Looks like one needs to name the subdirectories under maildir.  Is
this necessary?

If I have procmail writing to maildir and creating directories as
needed, then writing the numbered messages under that directory.  Do I
need to tell gnus about teh subdirectory?

We might see ~/maildir/group1

Then procmail might create maildir/group4.  Later maildir/group6 etc
Do I need to tell gnus in advance about these names? Or does gnus know
to look in maildir and recurse, the subdirectories.  Naming nnml
groups after them?

The examples in gnus info:
  Two example maildir mail sources:

          (maildir :path "/home/user-name/Maildir/"
                   :subdirs ("cur" "new"))

          (maildir :path "/user@remotehost.org:~/Maildir/"
                   :subdirs ("new"))

I won't always know the groups being created by procmail in advance.
I have procmail  setup to name groups after information found in the
Newsgroups: header.  This is an incoming nntpfeed being written to maildir.