When is pitching a 2nd yeast necessary?

[RallyFanatic]

I've seen the phrase 'pitching second yeast' thrown around a bit, and I was wondering what the purpose was.

My concern (read: paranoia) is that I've read up on 'modern' fermenting practices, and for the IPA I'm making this weekend I plan to leave it in the primary for a couple weeks, then rack to the secondary to dry hop for a couple weeks, then bottle for a couple weeks. Would I need to re-pitch yeast before bottling if it's been in some stage of fermentation for 4 weeks? Or will there still be enough yeast hanging around to carbonate the bottles? My OG should be around 1.060, with a final of around 1.014, if that helps.

 

[rwmiscik]

just let it be and let the yeasties do their thing. you shouldnt have any reason to repitch and as long as pitched the right amount of yeast in the beginning your yeast will fully attenuate and in a couple weeks you will have a delicious ipa. no worries

 

[dzlater]

I don't think you need to add more yeast
you might not need to dry hop "for a couple weeks"
check after a week and see how it's doing

 

[liebertron]

If you hold your beer in a primary or secondary fermenter for greater than six weeks you need to add more yeast. Not much though, its not like a complete culturing you do when you first cool your wort. Its a dry yeast addition before your priming sugar.