Shape: Northern Maidenhair Fern is a very attractive airy fern recognized by the dark slender leaf stalks (stipes) and the horseshoe shape outline of the rachis (formed by the rachis splitting into two divisions) which bears the long, narrow pinnae (the feather-like leaf branches), which are held somewhat horizontally. The stipes are usually very erect, and smooth, except there may be some scales close to the ground. Both rachis and stipes are black to purple-brown at maturity. Height varies from 14 to 20 inches.
Fronds: The fronds are 3-pinnate (3 times divided). The longest pinnae (side branches) are closest to the point where the branching of the rachis begins. Each pinnae will have 12 to 20 pinnules, usually oblong, at least 2x as long as wide, but the one at the tip of the pinna is more fan shaped. Each pinnule tapers at the base to a very short stalk. The upward facing edge of the pinnule has shallowly incised lobes. The veins of a pinnule can be forked but do not form a network. Fronds shed water leaving a smooth surface.
Fertility: For spore production the sori are on the outer margins (underside) of the pinnules. Many of the pinnules will have these marginal spore cases protected by little in-turned teeth - a false indusia, formed by the folded edge of the pinnule (an indusia is a flap of tissue that covers the spore cases).
Crosiers: Spring fiddleheads are pink to wine red. They grow from a creeping rhizome and clumps should be divided when you can no longer see the individual form of the fronds.
Habitat: Easy to grow in the home garden, Maidenhair fern should have moist, neutral to slightly alkaline, humus-rich soil and partial to full shade.
Names: The genus name Adiantum, is from two Greek words a, meaning 'without' and diainem meaning 'to wet', together meaning 'unwetted' referring to the smoothness of the fronds causing moisture to always run off them leaving them appearing dry, even after being plunged in water. The species name, pedatum, means 'like a bird's foot', referring to divisions that radiate outward from a common center - in this case the pinnae radiating outward from the horseshoe shaped rachis. The author name for the plant classification, 'L.' refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Above: The unfolding fiddleheads (crosiers) of spring. The stipes and rachis (stems and branches) turn black once the fronds form.
Below: A grouping of wine-red spring crosiers with the heads just unfolding.
Below: The forming of the fronds, usually in June, but earlier with an early Spring. Note the stipes and rachis already turning to the mature black color.
Below: Spore Development: Maidenhairs have many of the pinnules with marginal spore cases, on the underside of the pinnules, protected by little inturned teeth - a false indusia, formed by the folded edge of the pinnule. Inside, the spore producing organs (the sori) do their work. Note the fan shape of the pinnule at the tip of pinna and the oblong shapes of the others with one side entire and the other with shallow incisions.
Below: The fully developed form of summer. Note that the longest pinnae are where the horseshoe shaped rachis attaches to the stipe.
Notes: Maidenhair Fern is indigenous to the Garden area. Eloise Butler catalogued it on May 25, 1907. She first planted it in 1916 and in October 1917 she brought in 2 plants from Battle Creek in St. Paul. Her records also show that she obtained 50 plant roots of this species on Aug. 9, 1923 from elsewhere in Glenwood Park, in order to "dispossess wood nettle." Martha Crone planted 6 in June 1933 and then again years later in 1947, '48' and '52. In 1956 she set out 229 plants when she developed the Fern Glen. It has been frequently added to the Garden to increase the population. Cary George reported planting it in 1993. Susan Wilkins has planted some as recently as 2012 and 2013. It is native to the Minnesota woods in most counties of the eastern half of the state except the Arrowhead. In North America its range is east of the lower Missouri River and east of the Mississippi River (exc. Florida) and in the Canadian provinces from Ontario eastward. It is also found in Alaska.
There are nine species of Adiatum in North America and upwards of 200 in the world. Adiantum pedatum is the only Adiantum found in Minnesota and in most of the NE United States.
John Muir once noted that the dark stems of the Maidenhair were used by the Modoc Indians of California to adorn baskets with decorative brown bands. He would have been referring to one of the four species of Adiantum that grow in California. (Ref.: Summer Days at Mount Shasta.)
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"