Nope.
>>>>
Nowhere in the rules can I find a reference to "sacred groves", yet  nowhere in the world have I found a "mallorn grove".  And if not, what  items or beasts can be found in sacred groves?  
<<<<
Never quested in a sacred grove, so I can't tell you.
Mallorn groves need to be 'explore'd for; all the ones
I know of are hidden sublocations.  There isn't much
need for a mallorn grove, since you can get all the
drums you could ever want just by building something
outside of a city.  If there's any other use for mallorn,
it's slipped my mind.
>>>>
Thanks for your time.  Doug Christensen
Arlington, Texas,  USA 
-- Carl Burke cburke@mitre.org