How can I create own grass textures?

I’m trying to make my own terrain grass texture for Unity, but when I import my psd-files and paint them on the terrain there is always a bright border on the grass, like a halo.

When I preview one of Unity’s own grass textures, like grass.psd or grass2.psd, the background is transparant but when I open them in Photoshop they look like this:

alt text

I’m guessing this background prevents Unity from creating that annoying halo-effect on the grass texture, but my question is. HOW can make this on my own grass textures? How can I create grass textures with out bright annoying outlines?

All help is appreciated. Thanks.

Use photoshop to create an alpha layer in the channels tab