Don't spawn PCG points inside rocks?

I have a PCG graph that spawn plants on a landscape. Works fine. Except I want to avoid spawning plants inside (or close to) rocks that I place on the landscape. These rocks are not placed by PCG. I place them by hand. They are just static meshes. Of course, my PCG graph knows nothing about these rock static meshes, and so happily places plants intersecting with the rocks on the landscape. I’ve tried googling this, but everything I find assumes that you also spawned the rocks with PCG and so it tells you to use the difference node and/or bounds checks and so fourth. How do I check for the presence of these rock static meshes in PCG and then exclude points that overlap with them?