Christmas Fern Polystichum acrostichoides (Michaux) Schott    
Kingdom Plantae   >   Division Pteridophyta   >   Class Polypodiopsida   >   Order Polypodiales   >   Family Dryopteridaceae   >   Genus Polystichum   

Status:

Christmas fern occurs in northeastern and north-central parts of North America from New Brunswick south to North Carolina. It is hardy and abundant and has been documented in every county in Maryland.

Description:

“Lustrous, dark green fronds in circular, arching clumps from central rhizome" (Cobb, Farnsworth, and Lowe, 2005). Because Christmas Ferns are evergreen, they are evident all year round, including at Christmas-time, which may be one reason for their name. The margins of each leaflet, or pinna, has narrow fine teeth. A boot-like projection at the pinna base suggests a Christmas stocking, which is a helpful identification feature. Christmas Ferns have both sterile and fertile fronds, the fertile ones bearing markedly shorter, narrower pinnae near their tips. These smaller pinnae, which have tan spore cases (sori) on their undersides, are most noticeable in late summer and fall. Then the spores are shed and the pinnae that bore them dry up, while the rest of the frond remains green. The dry pinnae give the fern a diseased look, but this is the natural condition of the fronds after spore release.

Where to find:

Christmas Fern is especially common on slopes and banks of streams. It is easily observed in winter, when most other green forest-floor plants have died back for the year.

Relationships:

"Growing ferns and the accumulated detritus of past sterile fronds form a dense covering mass over the soil surface. This mass helps to stabilize the underlying soil and prevent or lessen erosion. It also generates a protective, concealing habitat for a number of ground feeding and ground nesting bird species.

"Because of their complex chemical composition, ferns are eaten by very few browsers or grazers. Fern densities in general have been increasing in many of the forests of Pennsylvania [and presumably of Maryland, too], due to the removal of competing, but more palatable, under-story plant species by the extensive browsing by the state's rapidly increasing deer population. This change in the forest under-story habitat structure has had wide-spread and deleterious impacts on the densities and successes of some mid-canopy birds (like the least flycatcher and the yellow billed cuckoo). Other bird species (like the wild turkey, for example) that use the concealing fern masses for their nesting sites have, however, increased in density in these "fern park" forests" (Penn State, Christmas Fern).

There are 860 records in the project database.

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Christmas Fern in Baltimore Co., Maryland (5/7/2017). Some of the fronds show narrowing of pinnae towards the frond tips, suggesting that these pinnae are fertile and will develop sori on their under-surfaces later in the season. Photo by Bill Harms. (MBP list)

Christmas Fern in Carroll Co., Maryland (6/18/2017). The pinnae shown in the right-hand photo are fertile, showing sori on their undersides. Photo by Bill Harms. (MBP list)

Over-wintered fronds of Christmas Fern in Baltimore Co., Maryland (3/11/2016). Photo by Kirsten Johnson. (MBP list)

A Christmas Fern in Garrett Co., Maryland (7/8/2012). Probably a sterile frond, because no sign of small, terminal, spore-bearing pinnae. Photo by Bill Hubick. (MBP list)

Christmas Fern in Anne Arundel Co., Maryland (5/19/2011). Spore-bearing pinnae shown in upper-right photo. Photo by Bill Harms. (MBP list)

Christmas Fern in Howard Co., Maryland (4/20/2010). Photo by Bill Harms. (MBP list)

Christmas Fern in Anne Arundel Co., Maryland (1/29/2017). Over-wintering fronds. Photo by Robert Ferraro. (MBP list)

Christmas Fern in Frederick Co., Maryland (5/2/2017). Fresh, new growth. Photo by Linda Lewis. (MBP list)

Christmas Fern in Howard Co., Maryland (5/26/2013). Photo by Joanne Solem. (MBP list)

Christmas Fern growing in Garrett Co., Maryland (10/27/2002). Shows characteristic "boot" at base of pinnae, and spines along pinnae edges. Photo by Boyer and McDowell. (MBP list)

Christmas Fern in Frederick Co., Maryland (6/25/2016). Appears to be a sterile frond. Photo by Dan Small. (MBP list)

Christmas Fern in Montgomery Co., Maryland (7/21/2015). These appear to be sterile fronds. Photo by Jim Brighton. (MBP list)

Christmas Fern in St. Mary's Co., Maryland (2/3/2018). Photo by Tyler Bell. (MBP list)

Christmas Fern in Charles Co., Maryland (1/16/2017). Winter appearance. Photo by Bill Hubick. (MBP list)

Christmas Fern in Calvert Co., Maryland (4/10/2021). (c) alexabely, some rights reserved (CC BY-NC). Photo by alexabely via iNaturalist. (MBP list)

Christmas Fern in Calvert Co., Maryland (2/29/2016). Winter appearance. Photo by Tyler Bell. (MBP list)

Christmas Fern growing in Kent Co., Maryland (3/26/2016). Photo by Nancy Martin. (MBP list)

Christmas Fern in Montgomery Co., Maryland (4/12/2014). New growth. Photo by Bill Hubick. (MBP list)

The sori of Christmas Fern in Calvert Co., Maryland (10/20/2016). Photo by Jim Stasz. (MBP list)

The sori of Christmas Fern in Calvert Co., Maryland (9/30/2017). Photo by Wayne Longbottom. (MBP list)

Christmas Fern in Calvert Co., Maryland (11/21/2020). (c) coxfamilydc, some rights reserved (CC BY-NC). Photo by coxfamilydc via iNaturalist. (MBP list)

Christmas Fern growing in Prince George's Co., Maryland (4/8/2016). Typical "fiddlehead" appearance of newly unfurling frond in Spring. Verified at inaturalist.org. Photo by Timothy Reichard. (MBP list)

Christmas Fern in Calvert Co., Maryland (4/14/2019). Shows "fiddleheads" of newly unfurling fronds. Photo by Wayne Longbottom. (MBP list)

Christmas Fern (sori on fertile portion of frond) in Howard Co., Maryland (5/26/2013). Photo by Joanne Solem. (MBP list)

Christmas Fern in Anne Arundel Co., Maryland (4/9/2011). "Fiddleheads" of unfurling fronds of Spring. Photo by Bill Harms. (MBP list)

A young Christmas Fern with developing sori in Howard Co., Maryland (5/6/2014). Photo by Nancy Magnusson. (MBP list)

Christmas Fern in Harford Co., Maryland (8/28/2016). Fronds all appear to be sterile. Photo by Kirsten Johnson. (MBP list)

Christmas Fern, shown growing on a bank as it commonly does, in Montgomery Co., Maryland (2/11/2017). Photo by Bill Hill. (MBP list)

Christmas Fern in Baltimore Co., Maryland (5/23/2020). (c) Dwight Johnson, all rights reserved. Photo by Dwight Johnson. (MBP list)

Christmas Fern in Talbot Co., Maryland (10/15/2020). (c) Wayne Longbottom, some rights reserved (CC BY-NC). Photo by Wayne Longbottom. (MBP list)

Christmas Fern in Charles Co., Maryland (11/28/2020). (c) johnbotany, some rights reserved (CC BY-NC). Photo by John Hall. (MBP list)

Christmas Fern in Charles Co., Maryland (11/28/2020). (c) johnbotany, some rights reserved (CC BY-NC). Photo by John Hall. (MBP list)


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