Foliage brush won't stack meshes

I am using the foliage brush to spread out crates, but when i run over the meshes it has placed, it just keeps adding more in the same space leaving me with a mess of intersecting crates. I’m trying to understand why the crates do not just stack.

It doesn’t do a trace onto foliage, for something like crates you’d have to position them more accurately than just brushing them onto a location anyway

Well, not tracing onto foliage sucks, but I am making a big cluttered mess, there is no need to position them with any accuracy.

Thanks for the info though, much appreciated.