Whenever you need to find actors in a level you need to use the get all actors of class node in Blueprints. Usually this is done on a one time event. Do not do this on a tick unless you use the DoOnce node.

Here I am using Get All Actors of Class in the level blueprint. If I press ‘J’ it finds all the plant blueprints I have and destroys them. If I hit ‘K’ it finds every Tree Blueprint, goes through each one in a For loop and sets the particle I have in the blueprint to visible.

Here is how I have the simple level set up:

The plant blueprint just has the plant mesh in there. The tree one has a particle I made and I set visible on the lower right hand side to off. That way I can set it to on in my level blueprint.