Palm grass setaria palmifolia

While I was driving around New Zealnd , near by Christchurch (10/15 frost every year and -4c ) I saw this amazing plant that look like a young coconut tree , but then after a closer look I realised that it was setaria palmifolia never seen it before and i was quite surprice to see that actually even if it look like a palm it`s actually an invasive grass .......


and this is the plant in flower