De or het schimmelvorming?

The correct Dutch article is:

de schimmelvorming

Rule Words ending in -ing: almost always de. See the rule

How to use schimmelvorming

the schimmelvormingde schimmelvorming
this schimmelvormingdeze schimmelvorming
that schimmelvormingdie schimmelvorming
our schimmelvormingonze schimmelvorming
your schimmelvormingjouw schimmelvorming
every schimmelvormingelke schimmelvorming
which schimmelvorming?welke schimmelvorming?
a big schimmelvorming / the big schimmelvormingeen grote schimmelvorming, de grote schimmelvorming