Lake Pupuke is unique in New Zealand in that all four obligate submerged members of the adventive Hydrocharitaceae,Vallis‐neria giganteaGraebn., and the “oxygen weeds”Lagarosiphon major(Ridl.) Moss ex Wagner,Elo‐dea canadensisMichx., andEgeria densaPlanch, co‐exist there. Dense stands ofVallisneria, up to 5 m tall, dominated the mid‐littoral zone (2–7 m depth) through to 1985.Egeriawas first recorded as present in Lake Pupuke in 1980. It occurred in the mid‐littoral zone and in 1982 it was estimated to occupy 2%, in 1983 10%, and by 1985, 25% of total macrophyte volume in Lake Pupuke. This trend suggests thatEgeriais the potential dominant of this community.