The Friends of the Wild Flower Garden, Inc.

Plants of the Eloise Butler Wildflower Garden

The oldest public wildflower garden in the United States

brittle bladder fern

Common Name
Brittle Bladder Fern (Fragile Fern)


Scientific Name
Cystopteris fragilis (L.) Bernh.


Plant Family
Wood Fern Family (Dryopteridaceae)

Garden Location
Historical - not extant


Prime Season
Early spring to frost


Fern terms


Shape: Brittle Bladder Fern is an erect to arching, clump forming fern with delicate fronds rising from 4 to 10 inches long.

Fronds - Fronds are either in sterile form or fertile form, looking the same but with the shorter sterile fronds appearing first in Spring. The blades are lanceolate (widest just below the middle), up to 3 inches wide, There are no aromatic glands. Fronds are produced throughout the growing season but they may die back is a dry summer, but will re-emerge with moisture. Blades are light green to dark green, and vary from bi-pinnate - pinnatifid to tri-pinnate from. The stipe is short, smooth, green to straw color, usually darker near the base, sometimes with a few scales and is brittle near the base.

Pinnae: The pinnae are lance shaped, usually 12 pairs, perpendicular to the rachis, opposite each other, or sub-opposite, and not curving toward the tip of the blade except perhaps at the tips. The lower pinnae are widely spaced and the lowest is usually a little downward pointing, typical of the Dryopteridaceae.

Pinnules: The lower pinnae will be cut into pinnules that have either lobed or toothed margins and are truncate to obtuse at the base. Upper pinnules may be entire. Pinnule veins will extend to the margin if toothed.

Fertility: The sori are placed on the back of the pinnule on a vein and widely spaced. Sori are rounded with a thin, ovate shaped indusia covering them, but open on the side facing the pinnule tip, like a pocket or bladder, and without glands.


Habitat: Brittle Bladder Fern grows in clumps or clusters from a creeping rhizome. Fronds emerge from the tip of the rhizome. It is found in rocky woodland soils, on ledges and cliffs. With adequate moisture it will be green all Summer. New fronds emerge all season.

Names: The genus Cystopteris is derived from two Greek words - kystis, meaning a 'bladder' and pteris, meaning 'fern', in particular a fern with certain type of indusium - one that is open on one side forming a pocket or bladder. The species fragilis means 'fragile' referring to the brittle stipe. The author names for the plant classification are: First to classify in 1753 with the name Polypodium fragile was '(L.)' which refers to Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. His work was amended in 1805 to the current name by ‘Bernh.’ who is for Johann Jakob Bernhardi (1774-1850) German botanist, Professor of Botany, director of the Botanical Garden at Erfurt. His herbarium collection is now in the Missouri Botanical Garden Herbarium.

At one time this species was subdivided into three varieties but those are no longer recognized. Another older species name that is no longer accepted - Cystopteris dickieana - has been folded into C. fragilis also.

Comparison ferns: Brittle Bladder Fern is similar to C. bulbifera, the Bulblet Bladder Fern, but that species has bulblets forming on the back of some pinnules, the blade is longer and it has glandular hair both on the rachis and the indusia. Brittle Bladder Fern also hybridizes with several other species such as C. tenuis, Mackay's Fragile Fern, which is also found in Minnesota and in some of the same counties. C. tenuis has pinnae that angle upward toward the tip of the blade rather than be perpendicular, and pinnule margins have more rounded lobes.

See bottom of page for notes on the Garden's planting history, distribution in Minnesota and North America, lore and other references.


Above: 1st photo - The shape of Brittle Bladder Fern frond. 2nd photo - Drawing courtesy Wisconsin Flora.

Below: The lower pinnae have fully separated pinnules with toothed to rounded lobes.


Below: Two views at different times of the indusiums scattered on the veins of the pinnules. In the second photo, as the sori mature, the indusium peels back and is severely degraded.

sori sori

Below: 1st photo - the stipe is brittle and has only a few scales. 2nd photo - the rachis is grooved on the upper side.

stipe rachis

large grouping


Notes: Brittle Bladder Fern is not indigenous to the Garden, but introduced by Eloise Butler in 1910 with plants sourced from Excelsior Springs, MO. She planted also in 1911, '13, '18, '19(2x), and '27. Martha Crone planted the species in 1934, '35, '37, '53, and 33 of them in 1956 when she developed the Fern Glen. Her 1934 planting was 15 ferns from Chisago County, MN and the 1956 group came from Orchid Gardens in Grand Rapids, MN.

The species eventually died out and is not known to have been replanted. Brittle Fern is a widespread species, found throughout North America except the SE section of the U.S. In dry areas it is found in higher elevations. Within Minnesota, it is found in the NE section of the state and then in scattered counties around the state but usually absent in the western section of the state and the far southern counties.

In North America there are 9 species of the Cystopteris genus, six of which are found in Minnesota.

Frances Theodora Parsons wrote in 1899: "This plant may be ranked among the earliest ferns of the year. In May or June, if we climb down to the brook where the columbine flings out her brilliant, nodding blossoms, we find the delicate little fronds, just uncurled, clinging to the steep, moist rocks, or perhaps beyond, in the deeper woods, they nestle among the spreading roots of some great forest tree. Their " fragile greenness" is very winning. As the plant matures, attaining at times a height of nearly two feet, it loses something of this first delicate charm. By the end of July its fruit has ripened, its spores are discharged, and the plant disappears. Frequently, if not always, a new crop springs up in August. We are enchanted to discover tender young fronds making patches of fresh green in every crevice of the rocks among which the stream forces its precipitous way.

Once more the woods are flavored with the essence of spring. In our delight in this new promise we forget for a moment to mourn the vanishing summer." From A GUIDE TO THE NAMES, HAUNTS, AND HABITS OF OUR COMMON FERNS

References and site links

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.

graphicIdentification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.