Echium pininana

It is a biennial or triennial weed, showing little more than leaf in the first year, but subsequently produces a dense, 4 metres (potentially) flower spike that carries a dense mass of leaves and small white/blue flowers.

Not on Nemba listing, however  the plant’s massive seed production is responsible for hundreds of seedlings popping up near the tennis courts amongst indigenous vegetation. They are being removed manually as they appear.