Shape: Ostrich Fern is a common and popular vase shaped fern as its upright green sterile fronds can reach 3 feet and in perfect conditions up to 6 feet - one of the largest North American ferns. It is named 'Ostrich' because the fronds resemble the plume-shape of the large ostrich feather. Fronds are either sterile or fertile.
Fronds - Sterile: They are 1-pinnate (once divided). They form a vase shape, tapering toward the base. The lowest pinnae (the branches off the main rachis [stem]) are reduced in size which gives this tapered appearance. Fronds are widest in the middle section. Each pinnae is attached alternately to the rachis giving a staggered appearance. There can be 20 to 60 pairs of pinnae with the upper ones slightly ascending. On each pinna there can be 20 to 40 pairs of lobes (pinnules) which are deeply cut, but not completely cut down to the central vein (the costa) of the pinna. These individual pinnules have a very noticeable v-shape vein pattern radiating from the midvein of the pinnule to the margin of the pinnule. These laterals do not branch. The rachis can have whitish hairs. The stipe (lower portion of the frond that does not have pinnae) is much shorter than the blade portion. Both the stipe and the rachis are deeply grooved on one side and rounded on the other.
Fronds - Fertile: The fertile fronds emerge much later and are much shorter, erect, green initially then turning brown in color with the fertile pinnae having inrolled segments (sori) to enclose the sporangia (spore forming organs) and these fronds have very stiff pinnae. In summer, these may be obscured by the taller sterile fronds. Like the Sensitive Fern, these fertile fronds will persist through the winter, providing landscape interest, and release their spores in the spring before the new fronds form. The stipe of a fertile frond is about as long as the blade portion, quite stout and erect, dark in color.
Fertility: The sori (which contain the spores) are on the margins of the fertile pinnae. The pinnae curl around the sori, enclosing them and forming a shape somewhat resembling a curved pea-pod about 2 inches long. These overwinter and break open in the spring to release the spores. Release is prior to the new sterile fronds unfolding. Spores germinate in 2 to 5 days.
The fiddleheads (Croziers) are stout and can be confused with those of Interrupted Fern except these do not have the whitish hair of the Interrupted Fern and unlike that fern the emerging fiddleheads of Ostrich Fern are edible and frequently sold commercially.
Varieties: There are two varieties of this species - var. pensylvanica, found in North America and var. struthiopteris which is found in Eurasia.
Habitat: Growth is from a large creeping rhizome which forms a crown which in mature plants will become elevated above the ground. Underground runners will propagate the species so clumps will spread and may be invasive - best not to plant it in an uncontrolled area. Divide in the Autumn. The proper growing conditions are moist, but not wet, rich soil, light to full shade. Full sun is OK if the area is cool and wet. They look good in drifts.
Names: An older classification for this fern is Onoclea struthiopteris. The older plant family was Onocleaceae. Not all botanists have agreed with the change of family to the Dryopteridaceae, but our Minnesota authorities following the lead of Flora of North America have done so. The current accepted genus name, Matteuccia, is in honor of Italian physicist Carlo Matteucci (1811-1866) whose main work was in bio-electricty. The species name, struthiopteris, is part Greek - struthos - meaning 'ostrich' and part Latin - pteris - meaning 'fern'. The author names for the plant classification are as follows: First to classify 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 1866 by ‘Todero’ who is Agostino Todaro (1818 - 1892) Italian Botanist, professor of botany at Palermo and then director of the botanical gardens in Palermo and it was he who created the honorary to Matteucci. His main work was Hortus Botanicus Panormitanus. The varieties listed above have additional authors.
Comparisons: The closest look-a-like will be the Cinnamon Fern, Osmunda cinnamomea, which is also vase shaped, but there the plant is not as tall, the blades are less tapered below the middle, the veins of the pinnules are forked and the fertile frond, which is also separate, has the fertile pinnae appressed tightly to the rachis. That plant also prefers more wet soils.
Above: Typical vase shape of the Ostrich Fern with the fronds being wider toward the top.
Below: The emerging fiddleheads of new sterile fronds. 1st photo - emerging alongside the prior years fertile fronds. Fiddleheads are edible. 3rd photo - Note the staggering of how the pinnae attach to the central rachis (Stem).
Below: 1st photo - The lowest pinnae on the rachis are reduced in size and have a tapered appearance. 2nd photo - Note the v-shape vein pattern on the pinnules.
Fertility: Spore production
Below: 1st photo - The new fertile frond which emerges about 8 weeks after the sterile fronds. 2nd photo - The fertile frond turns to a leathery-brown looking texture and color in July.
Below: The overwintering fertile fronds of Ostrich Fern. 2nd photo - note the sori (clusters of individual bumpy looking sporangia, each of which can produce up to 64 spores). These form on the rolled edge of the fertile pinnae, which arch outward from the central rachis - somewhat like a curved peapod. 3rd photo - some of the sporangia are opening exposing the individual spores.
Below: The sterile frond of Ostrich Fern. Note the decreasing size of the pinnae approaching the base of the frond, the gradual tapering toward the tip, making the middle the broadest.
Below. Historical photo - A group of Ostrich fern in the Woodland Garden, photo from a Kodachrome taken by Martha Crone, June 9, 1950.
Notes: In North America Ostrich Fern grows from Alaska to Newfoundland and south into the United States from the Dakotas eastward and south as far as Missouri and Virginia. It is the only species of Matteuccia in North America. In Minnesota it is well distributed in 2/3rds of the state, mostly absent in counties west of diagonal line drawn from Fillmore County northwest to Clay County. Although native to Hennepin County, Eloise Butler did not find it growing in the Garden area. She planted it in 1907, '08 '10, '12 and '14. Martha Crone also planted it in 1936 and planted 165 plants in 1956 when she was developing the Fern Glen. Ken Avery added another 75 to the Fern Glen in 1960. It occurs in a number of places in the Woodland Garden and in the Fern Grove.
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"