Identifying Silver Fern (Alsophila tricolor)

Take great care when identifying wild plants and fungi, this blog is not a resource to be taken by itself and further resources will be linked. Consult other sources and double check. While foraging is an extremely rewarding and useful skill, numerous common plants and fungi can make you sick or kill you. Be absolutely sure of what you’re eating and, when gathering, ensure you leave enough not only to ensure the survival and growth of the species but also enough for others to enjoy, from the human and more-than-human communities. Also cultivate an awareness of contamination and pollution – wastewater runoff, spraying, exhaust fumes – as this should affect your decision to harvest.

The Plant

Alsophila tricolor is a medium sized scaly tree fern in the Cyatheaceae family. They are native to Aotearoa, New Zealand and can only be found here. The genus name Alsophila comes from the Greek word “alsos” meaning glade or grove, referring to the shady forest habitat where ferns like to grow. The name “silver fern” refers to the silvery white underside of the leaves. The Māori name for this fern is “ponga” which is a general Polynesian term for the word “fern”, though silver fern is traditionally the only fern which is called ponga.

Description

Silver fern is a perennial tree fern which will grow to around 6 to 10 metres tall. Their fronds can grow up to 4m long from dens clusters of firm stalks covered with a silvery waxy bloom, but begin as a hairy brown koru’s in the centre of the fronds. Each soft leaflet grows from green stems and are a shiny green on top and a white/silver on the underside. The leaf stems are covered in tiny hairs on the underside. The trunk woody and fibrous and covered in brown broken off stalk ends and sometimes the immature ferns will have dead fronds skirting the trunk a bit but not on mature ferns. On the underside of some leaflets you can see little brown circles of spores which they use to reproduce sexually or they can reproduce asexually using rhizomes.

Ecology

Alsophila tricolor can be found in most native forests in the Aotearoa, though is not found on the West or South sides of the South Island. They are primarily found as a sub canopy layer in the bush and along forest margins and scrublands. They like semi shade or full shade in a sheltered position with moist soil, though when the ferns are more mature they can handle drier conditions.

Nutritional & Medicinal Information

Māori traditionally used the pith to make a poultice to treat skin diseases as it is known as an antiseptic.

Māori medicine also uses ponga gum to get rid of parasites in the intestines.

The woody fibre of the trunk is poisonous and the silver fern isn’t considered edible.

Possible Lookalikes

Milne’s tree fern (Alsophila milnei) looks similar to silver fern though they lack the distinctive silver underside.

Rough tree fern (Cyathea australis) also looks similar to silver fern though they are endemic to Australia and also don’t have white/silver stalks.

Interesting Facts

Māori traditionally made rough throwing spears , called Tārerarera, from mānuka which were sometimes tipped with ponga as the wood is poisonous.

Māori people believed that ponga once “lived in the sea” and that hunters would use the bright silver stalks and undersides of the leaves to find their way home. The fern leaves could catch the moonlight and “illuminate a path through the forest”.

The silver fern as a symbol has been used widely in New Zealand to represent industries from our army to milk companies to railways and most notably our sports teams.

Further Reading

Manaaki Whenua Landcare Research

iNaturalist

University of Auckland

Te Papa

New Zealand Plant Conservation Network