Abstract: The plant roots are embedded in a fibrous matrix material, which is oriented vertically. The matrix material is fixed to a support structure using a grid of fasteners. The support structure may be standard corrugated plastic sheeting, or a moulded plastic sheet. If biodegradable materials are used, they must be protected from humidity etc. The fibrous material is strong enough to support itself, and the embedded plants, between the fasteners, so long as the grid spacing of the fasteners is less than ¼-metre.