no it should not burn your leafs 6inches is fine and cfls barley give off heat at all. just have good air flow, fan blowing. and hps lights give off more of everything including heat. hope i helped you.

by the way i have the 42W cfls and i have them 2iches away and they dont burn it at alll.. but im sure the 150W would give more heat off so 6inches shood be safe