Coir mats, made of coconut fibres, provide a lining for wire-frame planters and window boxes. Coir is used as a replacement for sphagnum peat moss, as it's more readily available than peat and comes from a renewable resource. The fibres hold the soil and plants in place, while providing an attractive natural look to the basket. While pre-sized, preformed mats are available, you can also purchase coir matting on small rolls that you cut to size yourself. Sometimes the preformed mats must also be cut to fit into smaller baskets.
Soak the coir mat in warm water for 30 minutes to soften it. Squeeze the excess water from the fibres after soaking.
Push the mat into the basket, shaping it to the contours of the wire frame.
Trim the edges of the coir to the shape of the basket rim, using a pair of shears or a serrated-edged knife. Cut the coir so it overhangs the rim by no more than 1/2 inch. The coir must not sit beneath the rim of the basket.
Cut holes in the side of the coir, through the wire frame, if you want to plant in the sides of the basket. Make these cuts with a serrated-edge knife.
Some coir mats have a layer of plastic sandwiched between the coir fibres. These cannot be cut to size.
Cutting through coir can dull shears and knives.