If you want grasslands, you could cut up an old straw broom (or nylon broom and paint it). Glueing that stuff to the base could be a little tricky, though. You might want to try glueing a very thin piece of styrofoam (no more than maybe 1/4" thick) to whatever you use as a base for scenery (cardboard, hardboard, etc.) and then stick the straw into that to hold it while the glue dries.
Alternatively, you could use small balls of plaster, stick the straw into that and glue it. Or you could do the same sort of thing with two part epoxy (the putty style that comes in strips, not the liquid stuff that comes in a syringe). I don't know for sure how well any of these things would work, I've never tried it myself (I'll admit it, I'm just pulling ideas out of my rear here). I have a feeling that the two-part epoxy putty might be the best way to go in terms of strength and durability, unfortunately, it's also the most expensive stuff listed here. Hopefully some of this will work.
-Kev
This is all really good, take this advice I have some nice tips of my own to add on to these. That way you can get a liitle feed back. For one, I live in a grassland area, and if you want to go for it, also add in dome low clinging vegitation. Like no higher than the knee on an Eldar. This is because most often grass lands have very little trees, very few mountains, and there is a high wind rate. Which biologicaly means nothing as flimsy as grass will grow that high, because it will be torn from the ground.
Also, in modeling terms, some nice sturdy trees would look great but do them on single stands so you can spread them out, and keep them along the bases of the hills(wind protection gain). And with the epoxy it is expensive but no more than four or five bucks.
The grass, I have found that making this terrain that is really clogged with growth looks great and adds ton's to the game. But here is the problem, place a mini in it and it either falls over, or you brake off your grass. So leave little sections empty wo the it will be possible to place a model in it.
This is what I plan to do with my forest area, and I think it will work well with your grass too.. Also take heed to the pokeing the grass through styrofome this is a pratcical idea...