I saw this in a suburban garden in Hamilton. The leaves look awfully familiar – maybe from the botanic garden in Sydney, but that wasn’t flowering at the time. I think it might be a Horse Chestnut – Aesculus hippocastanum – but I wasn’t sure at the time.
Edit: Having done some research I discovered that they do actually grow in New Zealand. Obviously this is not a native plant. It originates from south-east Europe. The flowers are usually white with a small red spot; they are produced in spring in erect panicles 10–30 cm tall with about 20–50 flowers on each panicle.
This one however, appears to be much pinker so is probably Aesculus x carnea ‘Ft. McNair‘ – a Red Horse Chestnut which is a hybrid between A. pavia (red buckeye) and A. hippocastanum (horse-chestnut). There are a couple of cultivars currently available that offer very showy flowers. ‘Ft. McNair’ has bright pink flowers, each with a yellow blotch. The flowers are not tubular like those of the red buckeye, but are quite open and showy like those of its common horse chestnut parent
It is not known where it originated, but it probably first appeared in Germany before 1820. A medium-size tree to 20-25 m tall, similar to the parent species in most respects, but inheriting the red flower colour from A. pavia.
It is widely cultivated in streets and parks throughout the temperate world, and has been particularly successful in places like the United Kingdom and New Zealand, where they are commonly found in parks, streets and avenues.