Is particle density influence by orientation by default (horizontal vs vertical?)

So im doing some tests with the graswald particle system.
I make a horizontal plane, and a vertical plane that are connected and joint to be one mesh.

I applied 1 particle system, with a certain density and 10 interpolated children.

When I render it… the vertical plane seems te be a lot less dense than the horizontal one

My question is… is this cause by something? How would I achieve even density in this situation…?