I love the Foliage mats (or sheets) from Noch, Busch and others. Here's a couple of shots showing the new elevated section on the North Side of the layout (replacing the old elevated Kato Double Viaduct with super-elevated curves at 'grade' with the city)...
Noch 7408 "Nature & Pasture". Beautiful results (well, ignore the ballast mess at the edges!)! And it was so easy to apply....I used my standard method of white glue mixed with a bit of Mars Black acrylic paint, this creates a nice 'grey' color baser for the foliage to stick to (more here). I used two sheets for this hillside, and while this material is NOT cheap on a 'cost per square inch' basis (compared to the normal stock at hobby shops), and the fact that this 'hill' is in a very prominent area of the layout, I could afford to go 'high end' in this area!.
Very easy to work with as well, just cut the sheet to fit the area with normal scissors. The seams between the two sheets are almost impossible to find. When the foliage is sitting in the wet glue/paint mixture, all it takes is a little 'massaging' and the two seams sort of 'blend' into each other.
I have another sheet of this that is a bit more 'wild' than the pasture look I used on the hillside, not sure where I'll be putting this just yet, but I'll find a spot! You can tell what this stuff looks like in the below package (I've always found both catalogs and online shops somewhat unclear about this) next to the newly landscaped 'hillside'!