else do this:
in photoshop select the grass brush (single blade)
Make the background black, make a new layer
paint (in white) the blades for your grass brush/grass bundle)
Select the grass layer and copy it into the alpha layer of your map.
Clear the RGB and make it green (color variation if you want/more detailed)
Save it as TGA
Make a plane in Maya or other 3D program and add the texture to it.
Make the mesh to your liking (a cross, or 3 planes etc, just keep the polycount in mind)
Export the mesh and import it into Unreal (and the texture)
Check if the scaling is correct, if so, paint away! 
https://drive.google/file/d/0B-PazZV4rZqfTVNwd3B3eThTeUE/view?usp=sharing
Made this today using the same method!