New Zealand has narrowed down the options for its potential new flag design to include three fern motifs and a traditional koru emblem (+ slideshow).

Announced at a ceremony this morning, the four choices will be voted for by New Zealanders and pitted against the country's existing banner.

A government-appointed 12-strong jury cut down the candidates from the 40 potential designs unveiled last month, which were selected from over 10,000 designs submitted by members of the public.

The four shortlisted designs are Silver Fern (Black and White) by Alofi Kanter; Koru by Andrew Fyfe; and Silver Fern (Red, White and Blue) and Silver Fern (Black, White and Blue), both by Kyle Lockwood.

Voters will rank the four designs in a postal referendum between 20 November and 11 December 2015.

They will then decide in March whether to instate the new design and replace the current flag, which it has flown since 1902. If the replacement is chosen, it will be adopted six months later.

New Zealand prime minister John Key has led the campaign for a flag to replace the existing design, which features the UK's Union Jack motif.

Key has commented that the current design "symbolises a colonial and post-colonial era whose time has passed", as well as the similarities between the flags of Australia and New Zealand – also known as Aotearoa by the indigenous Maori people.

In Kanter's design, a fern frond sweeps from the bottom-left corner to the top right. The leaves and stem on the bottom half are white on a black background, with the inverse used on the other side.

"The fern has been a distinctive symbol of New Zealand for the past 100 years," said Kanter. "Strong and simple, it represents our uniqueness as Aotearoa New Zealand and the black and white colours show our 'yin and yang', with the softly curved spine of the frond binding us all together as a young, independent and proud nation."

Kyle Lockwood also used the fern prominently in his design, but integrated the country's current red, white and blue colour scheme, as well as its four stars – known as the Southern Cross.

"The red represents our heritage and sacrifices made," Lockwood said. "Blue represents our clear atmosphere and the Pacific Ocean, over which all New Zealanders, or their ancestors, crossed to get here."

"The Southern Cross represents our geographic location in the antipodes. It has been used as a navigational aid for centuries and it helped guide early settlers to our islands."

Another of Lockwood's designs that made the shortlist is almost identical, but swaps the red portion for black and the blue for a brighter shade.

Finally, Andrew Fyfe's Koru design is black on the right and white on the left, with a swirl of the two shades where they meet off centre.

"The koru represents the fern frond, but is also reminiscent of a wave, a cloud, and a ram's horn," said Fyfe. "In Māori kowhaiwhai patterns the koru represent new life, growth, strength and peace, and for this reason has taken a special place in Aotearoa's visual language."

The Flag Consideration Project is part of a current trend for crowdsourced design initiatives, which has seen the National Museum of Qatar take public suggestions for its new visual identity and Karim Rashid ask his Facebook followers to choose the facade for a building in New York.