Sedges have edges.
The rule to remember in identifying members of Cyperaceae - and although those edges are sometime pretty subtle, it holds true for our native species. They all grow in wet areas, if not right in creeks and ponds, which is another clue. The leaves, when present, are slender but with a substantial stem clasping basal sheath with fused edges. There is usually 3 stamens, and 2 to 4 feathery stigmas on the pistil. About 3mm wide, lengthy and joined to clasp at base of stem.