Adiantum, a genus of the plant family pteridaceae, includes about 200 species of maidenhair ferns. Some people say the ferns are named maidenhair because the plant has an aromatic oil that women used in hair shampoos or rinses to add shine to their hair, especially black hair. Of the 200 species, five are native to the US, 40 are native to China, and the greatest diversity of Adiantum species is in the Andes in South America. Maidenhair ferns range in size from less than one foot (about 30 cm) to 48 inches (about 122 cm) and differ in habitat temperature from tropical to sub-arctic.
Ferns are nonflowering plants that reproduce by spreading spores. The sorus is the part of the fern that makes spores and is located on the underside of a frond's female pinnules. Generally, a maidenhair frond consists of pinnae, which are the major lobes stemming from the center shaft, or stipe, and pinnules branch off the pinnae. One of the traits of the Adiantum ferns is that the stipes and main branches of the pinnae often are shiny black or dark purple. Most of the maidenhair ferns bear fan-shaped leaflets that are delicate on some species and coarser on others.
Adiantum ferns grow in various weather zones around the world. The rough maidenhair is native to tropical climates, such as Africa, New Zealand, and other regions. One place it grows is the tropical areas of North Queensland, Australia, where winter temperatures typically average between 60°F to 75°F (about 15°C to 24°C). In contrast, the northern maidenhair ferns have been known to withstand winter temperatures of nearly -50°F (-45.5°C) in Canada.
Most of the Adiantum ferns prefer to grow in moist wooded areas in half shade, such as on forest floors. Generally, they thrive in limestone-type soil with good drainage, but do poorly under trees that have needles and produce cones, such as pines and oaks. The leaf litter from these types of trees generates too much acid. When raising maidenhair ferns, a grower generally should avoid watering the fronds and water the soil instead. In Greek, Adiantum means "not wet," and the maidenhair fern fronds repel water when they get wet.
Although many ferns, such as the southern maidenhair or Venus hair fern, the Delta maidenhair, and the North American brittle fern, are suitable for greenhouse gardening, most are difficult to grow without added humidity. The petite, delicately textured A. diaphanum and the little A. tinctum, which has reddish young fronds, often make good plants for terrariums where the humidity is controlled. These terrarium plants usually have fronds that average in length from six to ten inches (about 15 to 25 cm).
In the past, people made a tea of the leaves of A. capillus-veneris, often called syrup of capillaire, and used it as a lung tonic. Traditionally in China herbalists made the same type of drink for not only throat afflictions, but also to reduce fevers and as an emetic to induce vomiting. Some people used to make a poultice for use on snakebites and skin disorders, such as impetigo. In the 1700s and 1800s, bartenders used the syrup of capillaire to flavor alcoholic drinks.
Uses of the Adiantum ferns depend on the species and the region where they are grown. North American natives continue the tradition of using the glossy, tough stems to decorate their baskets. Commercial growers raise maidenhair ferns for the floral industry to use as greenery in flower bouquets and arrangements. Hobbyists and gardeners often grow the ferns in woodland gardens or in areas of partial shade that replicate the natural or indoors as houseplants.