This grower is sure of this plant identification.
3 ft tall
aka Spiky Rush because of side facing hard flowers positioned down the stems
10 litre terracotta pot
Juncus genus (Rush). This genus contains about 280 species of grass-like plants, which are evergreen, tuft forming or creeping, mostly rhizomatous annuals and perennials. They all have either rounded leafless stems or stems bearing long narrow, basal leaves that are flat and hairless. The flowers have rounded heads and are generally inconspicuous; they have clusters of small brownish flowers. They are fully to half hardy, and will prefer sun or partial shade in a moist or wet situation.