When species first arrive in a new environment they experience what is known as a “lag phase”. This is a period of time when the populations is deemed insignificant or is unnoticed completely. After this phase populations of an exotic species can increase dramatically, resulting in a significant impact on the economy and environment. Because of this it is vital that potential pest species are identified and managed while they are still in the lag phase of colonisation.

Keystone Ecology assist the Christchurch City Council in controlling pest plant species that have escaped detection at customs and are beginning to establish in the Christchurch region, but are still in the lag phase of their colonisation. One such species is the polypody fern, Polypodium vulgare. Originally from northern Asia and northern North America, this small fern is classified as an Unwanted Organism in New Zealand and Keystone Ecology have been assisting with its management throughout Christchurch. To learn more about the polypody fern visit