Shape: Christmas Fern is an evergreen fern growing in circular arching clumps.

Fronds: They are dimorphic, that is the fronds are either sterile or fertile. Fronds are pinnate and do not have the pinnae divided into individual pinnules. Fronds have from 20 to 40 pairs of pinnae, the two lowest often point downward away from the blade plane. The lower pinnae appear opposite but from the middle of the frond upward they appear alternate. Sterile fronds and the non-fertile part of fertile fronds remain evergreen over winter, but usually flattened by snow load. The rachis is green and scaly. The stipes are grooved and scaly, with 5 vascular bundles. Stipe length is 1/4 to 1/3 the length of the blade.

Sterile fronds are once pinnate, arching, paler color beneath with hair-like scales. Above they are darker green and scaleless, also shorter and less erect than the fertile fronds.

Fertile fronds have both sterile and fertile pinnae. The upper pinnae are fertile and are much smaller then the sterile pinnae lower on the frond.

Pinnae: On all pinnae an auricle (lobe) at the upper side of the base points upward to the tip of the blade. The margins of sterile pinna have spiny tipped teeth that curve upward. Veins in the pinnae are forked and extend to the margin of the pinnae. Overall, the mature pinnae give the fronds a leathery dark green appearance.

Fertility: Sori are oblong, green initially then tan colored, covered with a circular indusia and in two or more rows on either side of the mid-rib on the reduced pinnae that form the upper 1/3 of the fertile frond. Indusia are thick, entire and blackish when dry. Since the upper pinnae are quite small, the entire underside seems to be covered.

Fiddleheads are scaly and stout with silvery white scales, appearing among the recumbent green fronds of the prior year.

Habitat: Growth is from a large compact scaly creeping rhizome that is long-lived. It prefers moist well-drained rich soil, neutral to acidic. They tolerate shade well, but if in a lot of sun, the soil must be moist. Soil in winter should remain dry. Clumps can be divided in spring or fall. Christmas Fern is a good fern for beginners in fern culture.

Names: The common name comes from the use of this evergreen fern for decoration during the Christmas time. The genus, Polystichum, is derived from the Greek Words polys, meaning “many,” and stichos, meaning “row” and together referring to the rows of sori on the type species for this genus. The species name, acrostichoides, means “like the genus Acrostichum” referring to the fern's resemblance to a group of Asian ferns not found in North America where the sori form a solid mass on the back of the pinnae of the fertile frond - as they do here.

The author names for the plant classification are as follows: First to publish was ‘Michx.’ which refers to Andre Michaux (1746-1802), French botanist who made many exploring expeditions in the U.S. collecting and cataloging many species. Two important works of his are the Histoire des chênes de l'Amérique septentrionale (1801 - Oaks of North America), and the Flora Boreali-Americana (2 vols., 1803, published posthumously). His son Francois, traveled with him and the father’s notes were later used for the 3-volume North American Sylva, for which Thomas Nuttall provided some supplements. Michaux's work was amended by ‘Schott’ who is Heinrich Wilhelm Schott (1794-1865), Austrian botanist who did extensive work on the Araceae family. His last position was director of the Imperial Gardens at Schönbrunn Palace in Vienna.