I am currently making a river scene. I have a few particle systems running such as grass. I am now trying to add a separate particle system to place cattails, but when I run it, only the tops of the plant are above the mesh. All the normal are correct. I've tried checking global on the location and that works for some, but others it puts in the sky since my scene is hilly. How can I tell the particle system to put the base of the plant at the base of the mesh?
Particle-duplicated objects will be centered on their origin points, also known as pivot points. You can move an object's vertices with respect to the origin point in edit mode by selecting all vertices and moving them until you have them where you want them in relation to the pivot.
Another option in object mode is to move the pivot with the options shown in Object > Transform > ... (I frequently use "Origin to 3D Cursor" and "Origin to Geometry.")