Shape: Bulblet Fern is an arching, clump forming fern with long but narrow delicate fronds from 12 to to 32 inches long but only up to 3+ inches wide on the fertile fronds.
Fronds - Fronds are either in sterile form or fertile form with the shorter sterile fronds appearing first in Spring. Fertile frond blades are narrowly triangular, widest at the base, with a long drooping tip. Fronds are produced throughout the growing season but they may die back is a dry summer, but will re-emerge with moisture. Sterile fronds look the same except shorter and slightly broader. Blades are light green to yellow green, and vary from bi-pinnate to bi-pinnate pinnatifid. The stipe is shorter than the blade, smooth, green, reddish-green, or straw color, usually darker near the base, sometimes with a few scales. Young stipes are reddish to pinkish.
The rachis of the blade and the costa of the pinnae are more yellow on top, dense with gland-tipped unicellular hair, and grooved on the upper side.
Pinnae: The pinnae are also long and narrow, sometimes drooping at the tips. Blades have 20 to 30 pair of pinnae, perpendicular to the rachis, not curving upward, alternately placed but the lower and larger ones opposite each other, or sub-opposite. The lower pinnae are usually widely spaced. Veins extend to the tips of the pinna.
Pinnules: Variable in shape - the lower pinnae will be cut into pinnules that have lobed margins and cut completely to the costa. Upper pinnules will be entire. Pinnule veins will end at the notches of the lobes.
Fertility: The sori are placed on the back of the pinnule between the margin and mid-vein. 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 with short glandular hair. The indusium will be severly degraded when sori are mature. In this species each frond can produce a small number of small green bulblets along the pinna costa or near the base of the pinna near the rachis. These are fertile and will germinate a new plant after they fall off if moisture conditions are right.
Habitat: Bulblet Fern grows in clumps or clusters from a creeping rhizome. Fronds emerge from the tip of the rhizome with stubs of old bases remaining. It can be found in rocky rich woodland soils, but usually on moist limestone ledges and cliffs. With adequate moisture it will be green all Summer. New fronds emerge all season.
Names: An older name for the species was Polypodium bulbifera. 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 - that resembling a pocket or bladder with one side open (unattached to the pinnule). The species bulbifera simply means 'bulb-bearing'. The author names for the plant classification are: First to classify was '(L.)' which is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy. His work was amended 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.
Comparison ferns: Bulblet Fern is similar to C. fragilis, the Brittle Bladder Fern, except that species does not form bulblets, the blade is shorter with a stipe that is brittle at the base and it does not have glandular hair.
Our species is known to hybridize with other Cystopteris species. Flora of North America (Ref. W7) has a list of known hybrids. One such species is C. fragilis and the resulting hybrid is C. laurentiana the Hybrid Bladder Fern, which has been found in six counties in Minnesota. Brittle Bladder Fern also hybridizes with several other species.
Above: A frond of Bulblet Bladder Fern, widest at the base, pinnae perpendicular to the rachis.
Below: The larger lower pinnae are opposite to sub-opposite each other; the rachis and costa yellowish with fine glandular hair.
Below: This frond tip shows immature sori, midway between the mid-vein and the pinnule margins, still covered by the indusium and several bulblets attached near the rachis. Note that the pinnae are now alternate.
Below: 1st photo - maturing sori. 2nd photo - veins extend all through the pinnae and on the pinnules end at a notch. 3rd photo - the stipe is mostly smooth and this one is a reddish green during the Summer, with a darker base.
Below: A cluster of Bladder Fern.
Notes: Eloise Butler introduced Bulblet Fern to the Wildflower Garden in 1908 with plants from the Minnehaha Falls area of Minneapolis. Many additional plantings occurred in 1909, '12, '14, '17, '18, '19 and 1924. Martha Crone planted it in 1934, 1950, and 158 plants in 1956 when she was developing the Fern Glen in the Garden, where several plants are still found today. Although there are no limestone ledges with cool mist in the Garden, the plant survives on the rich Garden soils.
Bulblet Fern is found in most of eastern North America except the Gulf of Mexico coast. It has also been found in the west in Utah, Arizona, New Mexico, Texas and Oklahoma. Within Minnesota is has been found in most counties along the eastern border, including Hennepin, Ramsey and Washington in the metro area, and most counties in the NE quadrant.
In North America there are 9 species of the Cystopteris genus, six of which are found in Minnesota.
Frances Theodora Parsons wrote in 1899 "The very spirit of the waterfall, all its life and grace, as it springs from the dripping ledges, clothing them with a diaphanous garment of delicate green which vies with their neighboring veil of white, now pouring over some rocky shelf a solid but silent mass of pale luxuriant foliage, now trailing down the cliff its long, tapering fronds, side by side with silvery strands of water, close to tufts of wind-blown, spray-tipped hare-bells. Although the plant is never seen at its best save in some such neighborhood as this, its slender, feathery fronds are always possessed of singular grace and charm, whether undulating along the dried rocky bed of a mountain brook or bending till their slender tips nearly touch the rushing stream or growing quite away from the rocks which are their natural and usual companions among the moss-grown trunks and fallen trees of the wet woods. From A GUIDE TO THE NAMES, HAUNTS, AND HABITS OF OUR COMMON FERNS
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"