Member of the Month: May 2009, Oct 2010, Sept 2017
Short answer (I'm wearing my dunce cap): Yes a ballast is necessary for pretty much any grow light you are likely to be using. Many CFLs have them built-in (those are the ones that you can just screw into a traditional home light socket). Most grow light bulbs won't even light up with 110v/220v. Require much higher voltage to start, etc.