How might i possibly get a lot of redwood leaves quickly on FTB Ultimate?
Are you referring to trees from ExtraBiomesXL? I initially thought you were talking about the much, much larger redwoods from Natura, which isn't in Ultimate.
I remember chopping those EBXL redwoods with mining lasers. Enough leaves usually decayed before they burned to let me plant another.
Mfr harvester with save leaves turned on and plant a couple trees and spam bone meal
Natura redwoods (the really, crazy big ones) don't seem to respond to bonemeal, although the EBXL ones should. I might recommend doing that to an existing tree- then, of course, smash some of the leaves yourself and plant a couple more at your base.
Or fly around and spam the Blade Launcher on your MPS Power Gauntlet- it acts as shears as well as a weapon. The shearing effect works on sheep, too- although, don't expect the blades to be able to to pass through sheep like they do with leaves.
If you're looking for redwood saplings rather than leaf blocks in one of the most recent packs, I can only recommend the Nature Scythe from Ars Magica 2. It's certainly the fastest plant-smashing tool I've seen since the Red Katar from EE2, although it's not easy to get. If I'm not mistaken, it's a rare drop from the Nature Guardian.