There are several maidenhair ferns. The one known in Britain by this name is Adiantum capillus-veneris, shown right. It is also called avenca (though this name is also used for the northern maidenhair and the fan maidenhair), black maidenhair fern, ladies’ hair, southern maidenhair, Venus maidenhair and Venus’ hair fern. It is a true fern, even though it bears little resemblance to ferns like bracken. It is not related to ginkgo, sometimes called the maidenhair tree because of a superficial resemblance of the leaves (inset).

The northern maidenhair, Adiantum pedatum, is also sometimes called the five-fingered fern or rock fern. It’s a much more familiar fernlike shape, as can be seen from the second picture. The fan maidenhair, Adiantum tenerum, is also called the brittle maidenhair and has leaflets which are very roughly diamond-shaped.

There are many other maidenhair ferns in the genus Adiantum, but the one covered in this post is the black maidenhair fern, which is the most useful from a medicinal viewpoint and will be referred to simply as maidenhair fern from now on. It is a small plant, and slow growing, and reaches a height of about 30cm (1′) or a little more, though individual fronds can reach a length of 50cm (20″). These have been used as a garnish for sweet food, and also dried for tea.

Maidenhair fern is found  growing wild across many continents, including North and South America, Africa, south eastern Europe and the Ukraine, Nepal and Turkey. Though not listed as a habitat in GRIN Taxonomy, it’s also found in Britain and many other warm temperate and tropical places, including Australia. It likes to grow on cliffs, rocks or in rocky crevices, often by the sea. It requires a semi-shady position and well drained neutral to alkaline soil.

Maidenhair fern is not frost tolerant and prefers a humid atmosphere, but it is often grown as a houseplant. If you choose to do this, stand the pot on a tray of shingle or large gravel, which you can keep topped up with water to provide the humidity it requires.

Both leaves (fronds) and roots (rhizomes) are used. Leaves are best used fresh, but can be dried for later use.

Many ferns contain toxic substances, but there is no record of toxicity relating to the maidenhair fern. However, due to the family history, it may be best for anyone suffering from a life-threatening condition to avoid using it. It is in any case not suitable for use by pregnant women. However, maidenhair fern is one of the oldest recorded herbal remedies, and it seems unlikely that someone wouldn’t have noticed if there was a problem, given that it has been used across the planet for thousands of years and is still used in many places today, though rarely in modern Western herbalism.

To make a standard infusion, put 3 handfuls of fresh herb or 30g (1 ounce) of dried into a warmed pot. Pour over about 500ml (2 US cups, 16 fl oz) of boiling water. Put the lid on and stand for at least 10 minutes up to 4 hours. Strain before use.

To make a decoction, use about 15 grams (a half ounce) of grated rhizome to 500ml (2 US cups, 16 fl oz) of cold water in a small pan. Bring to a boil, lower to a simmer and continue cooking until the liquid has reduced by half. Strain before use.

To make a poultice, crush the herb to a paste, adding hot water if necessary. To make the necessary pulp, you can add flour, cornflour or bread, mixing well so that the herbs are evenly distributed. Moisten a bandage in hot water and wring out, then spread the surface with the pulp and apply this to the area to be treated.

The fresh or dried leafy fronds are antibacterial, anticandidal, antidandruff, anti-fertility, antitussive, antiviral, astringent, contraceptive, demulcent, depurative, diuretic, emetic, weakly emmenagogue, emollient, weakly expectorant, febrifuge, galactogogue, hypoglycemic, laxative, pectoral, refrigerant, stimulant, sudorific and tonic.

Research in the 1980s found an anti-fertility (contraceptive) effect in rats; an extract prevented implantation, and thus conception. A 1989 study in Iraq showed that maidenhair fern is effective against E. coli, Staphylococcus, Proteus, Pseudomonas and Candida. A French study demonstrated its antiviral properties atainst Vesicular stomatitis. A study in Belgium in 1993 confirmed earlier research which showed that a water extract had an anti-hyperglycemic effect (lowered blood sugar levels).

The tea or syrup is used across the world as a soothing expectorant to treat bronchitis and respiratory disorders in general including colds and asthma. Another use which seems almost universal is as a treatment for hair loss (alopecia) and dandruff. Throat conditions such as laryngitis are also treated with maidenhair fern in many places. It is also used to promote or regulate menstruation, and in Brazil, as a childbirth aid.

A decoction is used in the Peruvian Andes for alopecia, gallstones, and jaundice.

Externally, it is used as a poultice on boils, bee stings, eczema, snake bites, and wounds. A paste made from the leaves is used in Nepal to treat headaches and chest pains by applying it directly to the area; a poultice would seem to be the easiest way to achieve this to avoid a potential mess!