Botanical name: Galium aparine
Family name: Rubiaceae
It is often considered to be sticky because it clings tenaciously to socks, other clothing and to sheep. However, the foliage and fruits are actually armed with tiny hooks which help them "stick" to such surfaces in a similar way to the hooks used with Velcro. (From: NZ Weed Database, Massey University).
Found a small cluster of plants growing in the back garden. Quite glad really, as it's getting harder to find a different weed each day.