[vince_refiti]

Gorse, as I understand it, was brought to New Zealand to be used as fencing between farm fields.

[merrua]

This seems likely since it was used for that back in the UK. Also the flowers were used for making dye.

[duckmannz]

I understood it was also because of the pretty yellow flowers and that it didn't grow so well in western Europe

[talideon]

It grows plenty well in western Europe.