Leather leaf fern is a generous amount of greens packed by weight. There are generally between 15 - 20 stems of leather leaf to each grower's bunch.
It's a good idea to rinse the stems off before inserting the greens into your vase design.
You can wipe down each individual stem with a paper towel.
The dirt and grime that remains on the stem can add bacteria to your water, so the cleaner the stems are before entering the vase the cleaner the water will remain.
I use the natural curve of the leather leaf to advantage when inserting from the sides of the vase.