Is there any way to use Minecraft Forge to generate a new block to a mod in the world?

For example, in my case, I need to, when a new world is generated, randomly place my new block on top of the grass in the world, but only in certain biomes, e.g. plains and jungles, much like pumpkins generate in their little groups. Is there any way I can do this?

Anyone?

Here's a tutorial I used to learn world gen - I haven't used these skills in a while though, so the tutorial might be outdated - http://wuppy29.blogspot.com/2012/08/forge-modding-132.html Just click on ore generation. If your going to want a similar system to pumpkins, you will probably want to select a random x and z coordinate pair then add some small random values to them each time you place a new block. That way you will have a sort of group of your block spawned. To assure that they lie on top of Grass, use a loop to start the random block's Y position at 0 and progressively increment it until the block at that position is Grass. Then, place your block at a Y position 1 greater than that.