[Antennas] Unused resonant antennas - shorted to ground or floating?

Thu Dec 24 16:00:43 EST 2009

OK, I see this stuff and don't pay a lot of attention to it and now I will need to know.
Example: Do I ground an unused 40 meter vertical antenna to make it be "invisable" and not affect the pattern (mostly) of another antenna that is 1/4 wave away and also on 40 meters (or do I let it "float")? 
Is it "good enough" to have it grounded by the Delta switch in the shack or does if have to be grounded AT the antenna? 
Tnx es 73, de Jim KG0KP