Missouri’s native maidenhair ferns (genus Adiantum) are perennials that spread with short-creeping rhizomes. Each frond is divided once or twice, and the leaflets (pinnules) are generally wedge-shaped or rectangular, with lobed outer tips. The leaflet veins are easy to see, and they divide by twos one to several times, forming a fan pattern (this pattern of the veins splitting again and again into twos is called dichotomous venation). Spores are produced on the undersides of bent-under edges of the leaflet lobes and are hidden by the bent-under edges. Spores are produced June–August. The leaves are deciduous (they drop off in winter or during dry conditions).
Missouri has two species of maidenhair ferns:
- Northern maidenhair fern (A. pedatum var. pedatum) is common statewide and is one of the most widespread ferns in Missouri. Its leaves are erect, with each leafstalk (petiole) branching into two arching stalks (rachises) at the tip, with each of these bearing additional stalks (the featherlike pinnae) attached along the upper (inner) side of each stalk (rachis); the pinnae bear the short-stalked leaflets (pinnules). In spring, the fiddleheads are pink.
- Southern maidenhair fern, or Venus hair fern (A. capillus-veneris), is scattered mostly in the Ozarks. Its fronds droop, and the leafstalks (petioles) don’t branch at the tips. Instead, the leafstalk is straight or somewhat bending as the leaflets branch off of it.
Frond length: 12–30 inches (northern maidenhair fern); 5–30 inches (southern maidenhair fern).
Northern maidenhair fern is scattered statewide. Southern maidenhair fern is mostly found in the Ozark and Ozark Border regions.
Habitat and Conservation
Both Missouri species of maidenhair ferns usually occur in moist, rich, cool locations. Southern maidenhair fern commonly grows on moist ledges and crevices of dolomite bluffs and boulders along streams, rivers, and spring branches. It can grow in dense colonies on bluffs along many Ozark spring-fed streams and rivers. Northern maidenhair fern is less common on rocks or boulders; instead, it is more often found on rich slopes of ravines in mesic (moist) upland forests.
Ferns have a two-parted life cycle. The portion of the cycle we usually notice represents the sporophyte generation, since it produces spores (not eggs or sperm). Each spore can germinate and become a plant representing the other half of the cycle, the gametophyte. People rarely notice the gametophyte-generation plants, which are tiny, green, flat, heart- or kidney-shaped leaflike structures. The gametophytes produce gametes (eggs and sperm), which must unite to create a new sporophyte plant. Water is needed in order for the sperm to swim to the eggs.
Several species of maidenhair ferns are cultivated as ornamentals indoors and outdoors. Their delicate feathery or lacy leaves with shiny dark stems makes them popular.
The genus name, Adiantum, has Greek roots and means “unwetted”: water rolls off the leaflets.
Maidenhair ferns have had a variety of medicinal uses by cultures worldwide, and some people still use them.
Plants that grow in wet places help to hold the soil in place during rains and floods.
Certain aphids, mealy bugs, an other small insects apparently suck the juices of maidenhair leaves, but mammals and other vertebrates generally do not eat it. Horticulturalists label some maidenhair ferns as “deer-resistant” since deer will not eat the foliage.
Unlike mosses and liverworts, which also have a two-parted life cycle, ferns and fern allies have a veinlike vascular system for carrying nutrients and water throughout their roots, stems, and leaves. As vascular plants, ferns are something like flowering plants. But unlike flowering plants, they do not have flowers, fruits, or seeds.
In case you’re wondering, the ginkgo tree (Ginkgo biloba) is sometimes called “maidenhair tree” because of its fan-shaped leaves with dichotomous venation — but ginkgos, which produce seeds and no spores, are not ferns at all.