Now let's pay attention to the greenery before inserting it into your clean vase.
Close examination usually shows greenery stems are still dirty and have debris clinging to the stems.
Before inserting them into your vase (which you've worked so hard to keep clean and contaminate free) - give your greening stems a good rinse to wash away the dirt before inserting them into your arrangement.
Wipe off excess debris with a quick swipe of a clean towel so you can tell they are clean.
You may have to remove some side laterals and cut the stems down before placing into the vase.