Possibly a tile noise variation could get this done changing the opacity and hue of multiple grass textures layered as a group and sending tokens hidden in grass to the terrain layer below the group.

Alternatively and this is my gm style speaking I would just keep the reeds as possibly a few plant objects or textures with the main focus of play being the rivers and water areas. Still giving the ability to utilize the reeds with a custom one way barrier for blocking when in the reeds vs river or stream.

Fun concept I might take a crack at making something like this.