Field checked: some white flowers evident ( a bit distant) that look like Sagittaria, and habitat more like Sagittaria than Alisma. Really this needs waders and protection agsinst blackberries.
Hi All. We had a look at these today. based on the flowers triangular stems and seeds we can say with confidence that these are in fact Sagittaria platyphylla. The Biosecurity team will look into the best method to treat as there are a large number of plants here.