There are some photos on Hat ets of my efforts, I use normal diy filler/plaster like polyfilla, allow it to dry, paint it with a base colour , then use mig African earth to top it, allow it to dry , then watered down pva mix all over, then use scatter, job done. eg Ruga ruga test shots.
Do you have a link to where you got the 'plants' from Bob?
I made some jungle terrain using fake plants, I based them on old cds using a blob of epoxy putty onto the surface of the disc.
Recently I bought some 'forest bases' - two shapes of thin laser-cut mdf, both the same shape (the bottom one slighty larger by a milimetet or so}. The top sheet has three 60mm diam. holes cut in it and three 60mm discs are supplied with it.
This allows a woodland base but you can also remove the trees to place troops on the base.
I got mine from 4Ground Miniatures http://www.4ground.co.uk/index.php
though I couldn't see them on the web-site when I looked.
Scroll down to plastic plants made by ZOO MED. One store canceled my order because this line of product is no longer being made so buy them now if you need them. I bought 5 bags of plants to make clumps of trees for a Darkest Africa wargame so I need affordable / easy to make bases.
In effect its a mat of sand and gravel glued to a fabric base for terrariums.
I use it cut into irregular shapes as rough terrain areas, though I do give it a coat of paint to consolidate the sand and match other terrain features. I guess you wouldn't need to paint it if you didn't want to.