Simple grass

I need to be able to fill a yard with grass. I intend to make 50*200 strips with grass and duplivert them around but, cannot remember how to make a transparent stencil on a plane.
Simple I know but…
I forgot
< sigh >

Dicon

Find an image with a blade of grass on it. The rest of the image MUST BE ALPHA!
Go into blender and turn the trasparency of the plane to zero, use the alpha grass texture influence the colour and transparency.
then it should work.