Climbing Fern

Jim and I performed a field survey for the Maryland highly state rare (S2) climbing fern (Lygodium palmatum) at a 15-acre location in Anne Arundel County, MD.  The notable features of the threatened fern include palmate lobed leaves, thin wiry and delicate stems that behaves like a true vine, which can climb clockwise, short distances up shrubs and coarse herbs.


Climbing fern (FACW) habitat is described as having an open understory, in moist thickets, and along stream margins.  The plant prefers acidic soils that are sandy and rich in humus, but nutrient-poor.  Peterson’s Field Guide to Ferns states that the plant likes light, moist or wet acid soil, in semi-shade of low thickets, open swamps, along banks of streams, in ravines where mountain laurel grows, and that it likes a certain amount of sunlight, but must have wet feet.  The Flora of Virginia goes on to state that the plant occurs in floodplain forests and swamp hummocks, depression swamps, mossy ditches and ecotones of seeps and seepage swamps, usually in extremely acidic and infertile soils.

Throughout this blog entry, I’ve added photos of the Maryland State threatened plant, as observed on March 18, 2016.


The site included a perennial stream channel and side slopes having soils that are classified as Sassafras and Croom, 15 to 25-percent slopes, with some areas of 25 to 40-percent slopes, characteristic of ravines, swales, drainage-ways and drain-heads, consisting of fine sandy loam.  Up and out of the active channel and side slopes, the soils change to a Patapsco-Evesboro-Fort Mott complex with 0 to 5-percent slopes, consisting of sand and sandy loam, occurring on summits.


Three forest types occur within the study area, which include “in-channel and hardwood side slopes,” “forest floodplain,” and “Virginia and Loblolly pine, conifer monocultures.”


Species observed within the in-channel and steep slopes of the riverine perennial (R2) channel include chestnut oak (overstory dominant), southern red oak, white oak, willow oak, red maple, black gum, sweetgum, river birch, tulip poplar, pin oak, American holly, persimmon, sassafras, hickory, black walnut, black cherry, Virginia pine, loblolly pine, flowering dogwood, mountain laurel, highbush blueberry, lowbush blueberry, azalea, sweet pepperbush, sweetbay magnolia, multiflora rose, Asiatic barberry, iris, copious amounts of common greenbriar, partridgeberry, poison ivy, Japanese honeysuckle, deertongue, running ground cedar, speedwell, spleenwort, New York fern, dogbane, wineberry, Allegheny blackberry and purpletop.


The relatively mature “riparian” stand has an average 15-inch diameter overstory, dominated by chestnut and other mixed oak species.  I noted a few large oak that may exceed 30-inches diameter and a few also that are on the edge of vertical escarpments, subject to eventual collapse due to active slope sloughing.


The forested, active floodplain includes large areas of forested and emergent wetlands (PFO/EM1B).  Observed plant species include red maple, river birch, black willow, American holly, pin oak, eastern red cedar, sweetbay magnolia, sweetgum, smooth alder thickets, autumn olive, sweet pepperbush, multiflora rose, Japanese honeysuckle, poison ivy, grape, Asiatic barberry, Asiatic bittersweet, common greenbriar, Phragmites, deertongue, soft rush, three-way sedge, skunk cabbage, broomsedge, Microstegium, wood-reed grass, cress, wild onion and bluegrass.  I noted significant amounts of deer browse/coppice.


The upland conifer stands were near monocultures of loblolly in one case and Virginia pine in the other, where a high degree of pine recycling was evident in the Virginia pine stand, with young hardwoods punching through to become intermediate and associate species.


I found only one aggregation of climbing fern, in an area of about 50-feet by 20-feet, and consisting of approximately 20-plants.   All of the plants were growing on the banks of the R2 stream channel, at about face height four to six feet above the stream invert, and occurring in moist, sandy soils, with about 65-percent canopy closure.


The ferns were climbing on host common greenbriar, Japanese honeysuckle, sweet pepperbush, moss and on bare, sandy soil.  The aggregation was GPS field-located and numerous photographs were taken, then with a report and map prepared.


Climbing fern is semi-evergreen and the RTE plant survey was performed on March 18, 2016, at the very beginning of the growing season, when it is more conspicuous, as little other green vegetation is present.  Some ruderals were flowering and Japanese honeysuckle was beginning to leaf-out.


Otherwise, very little new growth was competing with the ability to look for the plant (seeing the forest through the trees).  The downside of a late-winter survey is not being able to take photos of the plant when it is fresh, green, robust and has its upper fertile leaflets.


What a very cool find!  Thank you Jim and Dave for your help with the office and field work.


According to Northeast Ferns, Lygodium palmatum was first described by famed colonial botanist, William Bartram in Georgia, but he failed to give the plant a valid name, until 1801, when named by Swartz.  This fern was the first plant species to be protected by law in 1869 by the Connecticut legislature, as the plant was picked to near extirpation for Christmas decorations, Christmas wreaths and plant press wall hangings.

The 1910 Forrest Shreve, The Plants of Maryland document the occurrence of climbing fern in Millersville, Anne Arundel County, MD.  The 1919 Hitchcock and Standley, Flora of the District of Columbia and Vicinity document climbing fern at several restricted localities at the Riverdale swamp, vicinity of Suitland, Lanham and Arundel.  The 1984 Brown & Brown, Herbaceous Plants of Maryland states the fern occurring in moist thickets and open woods in Anne Arundel County, MD.

The Survey of the Vascular Flora of Anne Arundel County as compiled by Colby Rucker note the following habitat information “Shaded or moist grassy places” (Gray 1867).  “In moist thickets and open woods” (Britton 1901).  “Wet thickets in sandy or acid soil” (Radford et al 1968).  “Terrestrial in woods, thickets, and at bog margins, in humus-rich, slightly acid soil (Lellinger 1985).  “In large colonies on sandy soils of wet deciduous/evergreen forests” (Redman 1991).

Frequency:  Mapped by Reed (1953) in Anne Arundel, Prince Georges, Montgomery, and Harford Counties.  “Rare; Anne Arundel, Calvert, and Prince George’s Counties” (Redman 1991).

Heritage Rating:  1988: B2 (Highly State Rare). 1991:  Threatened.

Records:  Wet thicket Nov. 1890, Katherine A. Taylor (US) (Stieber 1967).  Junction of Benfield Road and Coolspring Branch near Butler estate (Plitt 3/28/1903).

Two stations near “Forest Home” on Marley Creek watershed (Plitt 5/2/1903, 4/29/1905).  Severn Run above Dicus Mill (Plitt 1/30/1906); this is the largest station in Maryland, with vigorous colonies of plants in sandy thickets along Severn Run.  “Millersville” by P. H. Friese (Shreve et al 1910).  Dicus Mill Road, in wet woods along the Severn Run 9/26/1951, Clyde F. Reed (US) (Stieber 1967).

Four stations (upper county) mapped by Reed 1953.  Severn Run 10/31/1982, 3/6/1983, 7/12/1986, 6/22/1987 (at Dicus Mill), 6/-/1987 (at Gambrills Road), 7/9/1988, 12/21/1991 (behind Millersville P.O.) (Sipple 1993).  “Ben Oaks” 5/13/1998; Sipple 1999, p.350.

Sightings:  Rear of Crouse property, on hilltop adjacent to Severn Run park property.  Indian Creek Branch; small station on mountain laurels at rear of lot at end of Larue Road, by Rucker & Todd Davison ca. 1986.  Relocated by Rucker & Julie Robertson; extant 1989.