Shape: Spinulose Wood Fern forms an arching vase shape with glossy deeply cut fronds.
Fronds: Fronds are up to 30 inches long and up to 12 inches wide. Sterile fronds stay green into the winter, fertile fronds die back. The blades are oval to triangular with the lower half of the blade much the same width before tapering to a fine tip. The stipe can be 1/4 to 1/3 the blade length and both it and the rachis will have some residual brown scales. Blades are 2 to 3 pinnate, but the outer tips of the pinnae are seldom cut all the way to the mid-rib with the result that the form is frequently 2 to 3 pinnate-pinnatifid.
Pinnae: Most pinnae angle upward. The base pinnae is usually shorter that the adjacent pinnae but the pinnules on that basal pinnae are an important distinguishing characteristic.
Pinnules: Pinnules have toothed margins with some bristles on the tips that curve toward the outer tip of the pinnule. A characteristic of this species is that on the basal pinnae on the rachis, the basal pinnule is longer than the adjacent pinnule above it.
Fertility: The sori on the fertile fronds are small and located on the underside of the pinnule halfway from the midvein (the costule) to the pinnule margin. They are covered with an indusium. Spores are mature by July.
Fiddleheads: These are not particularly hairy but do have brown scales, some of which remain on the stipe and on the rachis.
Habitat: Like most Wood Ferns, this species likes rich, moist, neutral to acidic soil in partial to full shade. They are long-lived plants and do not need to be divided periodically. But the rhizome is short-creeping and does form clumps which usually have a number of old stipes showing.
Names: The genus name Dryopteris, is derived from two Greek words, drys, meaning 'tree', and pteris, meaning 'fern'. Many members of this genus are commonly referred to as "wood" ferns and hence the name. The species, carthusiana, has two possible origins: The first - it is an honorary for botanist Johan Friedrich Cartheuser (1704-1777) - the second is that it is named after the French village of Carthusium in the Dauphine where the first plant author found it. The author names of the Plant Classification are first ‘Vill.’ which refers to Dominique Villars (1745-1814) French botanist who described over 2700 plants in Historie des plantes de Dauphine. His work was amended by ‘H.P.Fuchs’ which refers to Hans Peter Fuchs (1928-1999) Swiss botanist and plant taxonomist whose work was mainly in SE Asia. An older botanical name for this this species is Dryopteris spinulosa and older still is Aspidium spinulosum.
Comparisons: Other members of the Wood Fern Family found in the Garden are Goldie's Fern, Dryopteris goldiana; Marginal Wood Fern, Dryopteris marginalis; Male Fern, Dryopteris filix-mas; and Crested Wood Fern, Dryopteris cristata. Spinulose Wood Fern is best identified by 1) the longer inner-most pinnule on the basal pinna, 2) the toothed margins with bristles that curve upward on the pinnule tips and 3) no glandular hairs on the blades.
Above: 1st photo - A clump of Spinulose Wood Fern. 2nd photo - Pinnules have teeth and bristles on the teeth that curve toward the tip. Note the upper lobes are not cut through.
Below: The divisions are 3 pinnate-pinnatifid as the pinnules only have some of the lower lobes fully cut to the costule. Shown is the lowest pinnae. Note that on the lowest (the basal) pinnae (the one to the right of the rachis in the photo below), the lowest pinnule is longer than the one above it - a defining characteristic.
Below: The Fiddleheads of April. Some of the brown scales are retained on the stipe (3rd photo) and the rachis during the growing season.
The Fertile Fronds; Sori are found on the pinnules halfway between the midvein and the margin. 2nd photo - the indusium is falling away and at right the dark brown sori indicate maturity and release of the spores.
Notes: Spinulose Wood Fern is indigenous to the Garden. Eloise Butler catalogued in on May 25, 1907. She also planted it in 1911 using the older name, Aspidium spinulosum, with plants sourced from Gillett's Nursery in Southwick, MA, and again in 1918. Curator Martha Crone planted it in 1934, '35 and '37 and again in 1956 when she developed the Fern Glen. By the time of her 1951 Garden census the name in use was Dryopteris spinulosa. It has been planted most recently in 2006 by Curator Susan Wilkins.
Spinulose Wood Fern is found throughout Canada and in the U.S. it is found in all the northern tier states, Washington and Oregon, eastward to the east coast, except Wyoming; and then southward along the Mississippi River to Arkansas and eastward to the coast - basically the eastern half of the country plus the western northern tier states. In Minnesota it is found in most counties except in the SW quadrant. Ten species of the genus Dryopteris are found in Minnesota.
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"