What are ferns?


What are ferns?

Ferns belong to the family technically known as Pteridophytes. The word “Pteridophytes” comes from the Greek words “pteris” meaning “fern” and “phyton” meaning “plant”.

Ferns are among the estimated 10,560 species of plants that reproduce by spores – producing neither seeds nor flowers. Fronds of the largest species of fern can grow up to six metres long!

Ferns can be dated back some 360 million years to the Carboniferous period and formed the forests that later fossilized into coal.

Paleontological evidence indicates that the Fern Osmunda claytoniana has remained unchanged for at least 180 million years!

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Examples of Pteridophytes

Great horsetail Equisetum telmateia © Ita McCobb

Examples of Pteridophytes include Ferns (Embryophyte/Polypodiaceae), Clubmosses (Lycopodiopsida) and the Horsetails (Equisetum), which are today considered to be a living fossil as they are the only living genus of the Equisetopsida family, which millions of years ago could grow up to 30 meters in height!

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Fern characteristics

Fern fiddleheads © Ita McCobb

Ferns are “vascular” plants – that is, having an efficient internal conducting system of vessels that transports water and salts upwards and food downwards – and so they tend to grow quite large unlike mosses that are what are called “non-vascular” plants – that is, they do not have water-conducting roots or vessels – and so tend to be very tiny plants!

They have curled stems (called “fiddleheads”) that open into leaves (called “fronds”), roots and sometimes true stems. Tree ferns are Pteridophytes that, unusually, have full trunks.

Many ferns from tropical rainforests are Epiphytes (a plant that grows non-parasitically on a tree or other plant); their water comes from the damp air, water-soaked terrain and host plant and from rainfall running down branches and tree trunks. There are also some purely aquatic ferns such as the Water fern or Water velvet (Salvinia molesta) and Mosquito ferns (Azolla family Salviniaceae).

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Lifecycle of Ferns

Hard fern Blechnum spicant spores © Ita McCobb

Like Bryophytes (mosses and liverworts), Pteridophytes do not produce seeds or flowers but reproduce via spores. Their reproductive system consists of two distinct consecutive generations – the normal plant produces non-sexual reproductive bodies called “spores”, which are contained within tiny capsules called “sporangia”, which form on the underside of their fronds (leaves).

When the spores germinate they develop into extremely tiny, quite independent plants called the Prothallus, which bears microscopic male and female organs (sometimes on one plant, other times on separate plants).

When the egg in a female organ is fertilized by the sperm from a male organ (which can swim like those of animals) it grows into a new Pteridophyte plant.

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Fern uses & ecosystems

Common polypody Polypodium vulgare © Ita McCobb

Ferns help fight soil erosion. Their complex root system helps maintain soil stability. Ferns are popular in Asia where the Azolla fern is used as a natural fertilizer for rice crops.

Ferns are also used homoeopathically (mostly in Asia) for treating ailments ranging from expelling parasites to treating bowel disorders, coughs and lung problems – since ingesting some ferns can also cause you to be quite ill these are remedies best left to the professionals!

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Typical Ferns

Examples of common ferns you are likely to come across are: Clover fern, Bracken, Hart’s-tongue fern, Spleenwort, Horsetail, Horsetail cones (Spore-heads) and Clubmoss.

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References: United Nations Environment Programme (UNEP), Division of Technology, Industry and Economics; Botany for gardeners, Brian Capon, Third edition, Timber Press; Colour Identification Guide to the Grasses, Sedges, Rushes and Ferns of the British Isles and north-western Europe, Francis Rose, Viking, The Penguin Group; Royal Botanical Gardens, Kew, London; Missouri Botanical Garden; Latin for gardeners, Lorraine Harrison, Royal Horticultural Society; International Botanical Congress (IBC); Oxford English Dictionary, Oxford University Press.