Hair Particles "growing" outside the surface

Hi. I am setting a hair particle system and use it as trees.
I checked the settings of the particle system, but I could not find why this is happening.

Particle_Error

The trees should grow only on the emission surface.

Thank you

Has the plane a modifier? I am not really sure here what the problem could be. Did you checked the particle hair system without the objects if its in the correct place? Maybe the trees have a wrong origin to put the origin at the base of the trees.

Hi ! Thank you for your fast response. The trees have the origin at the bottom. Also the plane does not have any modifier more than the “particles” modifier.

I am wondering if it has to do with the trees in the location not having the scale applied.

I think the normals of the emission surface were not working correctly. I flip some of the meshes and now it seems to work.

Thank you

Yep with something like that the first steps are checking normals, apply scale loc and rot and see where the origin is.