Blocks of Parchwood Leaves can be harvested/pulled with your arctek-gauntlet without needing any Power Cells. If you use Stone Mining Cells or better to pull leaves, these stronger Power Cells will not even lose durability.
In Creativerse leaves will not decay / vanish by themselves when you "cut" down the stem of the tree nor if you take away all the wood-blocks that the tree is made of. Instead the blocks of leaves (as well as all Flower-blocks, Beeswax, Vines, etc.) will prevail and float in the air until you take them down manually or use Excavators on them to collect at least half of them.
You can of course also throw Explosives at leaves and/or burn them. As leaves are inflammable, burning them might work overly well in warm environments. So beware of forest fires that will also burn down all the wood, Shrubs and Savannah Tallgrass! On the other hand burning attempts might stay below expectations in cold environments. Simple torches cannot even set fresh leaves aflame in snowy biomes (as of R25 in November 2015).
One block of Parchwood Leaves can be made into 4 blocks of Shredded Leaves in the Processor. Taking/crafting Shredded Leaves will unlock the recipe for three types of colored carpets. Shredded Leaves burn even easierly than fresh leaves when being placed (even on snow) and can be used as a fuse for Explosives very well.
Parchwood Leaves can be used as Fuel for the Forge, however 4 blocks of leaves are needed and used up for each melting-/hardening-process. Also each melting-/hardening process in the forge will take quite long when you use leaves as fuel.
Parchwood Leaves cannot be corrupted into Corrupted Leaves currently (as of R25 in November 2015), but the stems of Parchwood-trees can - meaning Parchwood-blocks - for example by using Corrupt Bombs on them. By that Parchwood will turn into better fuel, but it has to be picked up using Lumite Mining Cells, which will reduce the durability of the Mining Cells quite a bit (just like pulling all other kinds of corrupted blocks).
If you purify these corrupted wood blocks, they will turn into Cragwood, even if they were Parchwood before being corrupted.
You can plant Queen Bees on Parchwood Leaves to grow Beeswax, which will take ca. 3,5 hours (real-life time). Currently (as of R25 in November 2015) you cannot grow Parchwood-trees from Saplings, and there are no Parchwood Flowers.