​Which of New Zealand’s flora species have come from elsewhere?

​Which of New Zealand’s flora species have come from elsewhere?
 
Thanks to New Zealand’s geographic isolation, we can boast that as much as 80 per cent of our plantlife is endemic – that is, it only exists in New Zealand!
 
However, there are also plenty that have come from further afield. While some of them are completely harmless, some are considered as pests that need to be actively controlled so as not to harm our endemic species.
 
Here are a few top examples of invasive flora species.
 
Didymo
 
Potentially the most talked about and well-known example at present, didymo was first discovered in the country in 2004, which was the first time it was found in the Southern Hemisphere.
 
Didymo is a freshwater algae that can be hugely damaging to water quality, and to the flora and fauna living in that water. Unfortunately, it is extremely easy to spread didymo, as it only takes one cell in one drop of water to spread to a new waterway. New Zealanders and conservation workers alike are fighting to stop this algae from entering new water supplies.
 
Gorse
 
Gorse bushes are an extremely common sight all over New Zealand, and it’s estimated that they cover as much as 700,000 hectares of land. Gorse spreads easily and is incredibly tough to control, as huge amounts of time, effort and money have gone into various strategies to cut down on gorse populations.
 
This species isn’t all bad though, as it is used as a windbreak throughout Canterbury, and has been shown to help grow native plants.
 
Agapanthus
 
Proving that not all invasive species are terrible, the agapanthus flower was introduced to New Zealand and is now commonplace in gardens throughout the country.
 
While it’s technically listed as a weed, these flowers at least offer a pop of pleasing colour to the eye! 

Gorse isn't all bad news it can act as a nursery for young native trees. photo credit NZGOVT