nut grass, like a string of pearls

This is a plant that grows relentlessly in the Northey St beds. They propagate via underground rhizomes, so each of these "nuts" can grow into a new set of grass blades, which remain connected by the thin root strands. 

When weeding, loosen the entire patch soil first, so that when you pull out the plants, you also get out the roots, the connecting network of roots, and the nuts.