1:72 is quite small so here´s what I´d do-
I´d try to find some fine roots from a tree (these can be used as branches in dio´s) and use those. However, if you live in the city this can be quite difficult.
You might want to try fine steel wool and paint it.
If you want leaves you could try fine, coloured sawdust or even spices, like oregano and such.
For longer grass you could use hemp rope.
Experiment a lot.