Can we Plant tree on Planes Instead of Terrain using Procedural Placement

I have Created a Procedural Island Using Perlin Noise and a Plane. I dont know how to place trees on Planes using a Script , like we paint trees on terrain, but i want to do it using Script and Procedural Placement/Generation on a Plane Not a terrain,(Or we cant do it on a plane ?) Can any one Help me about this, can any one tell how can we that and procedurally place trees on plane using a C# Script . Please any one Help me.