This page shows the process I use to make 4mm scale hedges. These hedges really come into their own when they are used in conjunction with a wire and post fence.
Materials
I use the following materials:
Polyfibre wadding (sprayed brown)
2mm brown static grass
Finely sieved sawdust pigmented with Sage Green household emulsion paint
Finely sieved autumn leaves (because my layout is based in autumn)
Place some "jute string bushes" along the line of the hedge. The density of the placement will depend upon the required look of the hedge.
Tease out small pieces of the brown painted poly-fibre, and place in the hedge line. Small peices layers appear to work better than large pieces.
Using PVA glue diluted very heavily with water and a dash of detergent, drip small drips onto the poly fibre and the just string bushes. You may need a squirt or IPA to break the water tension.
Sprinkle the finely sieved leaves on to the glue droplets
Fix with cheap hairspray (not forgetting to mask other areas)
Sprinkle more finely sieved leaves on to the glue droplets
Fix again with cheap hairspray (not forgetting to mask other areas)