De or het bomenstichting?

The correct Dutch article is:

de bomenstichting

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

How to use bomenstichting

the bomenstichtingde bomenstichting
this bomenstichtingdeze bomenstichting
that bomenstichtingdie bomenstichting
our bomenstichtingonze bomenstichting
your bomenstichtingjouw bomenstichting
every bomenstichtingelke bomenstichting
which bomenstichting?welke bomenstichting?
a big bomenstichting / the big bomenstichtingeen grote bomenstichting, de grote bomenstichting