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Cyrtomium is a genus of approximately 20 species of ferns in the Dryopteraceae family and are native to Asia. One of the most popular, Cyrtomium falcatum, also known as the Japanese holly fern, is a species that is widely grown as a fill-in for ornamental borders and as a house plant. It has escaped cultivation in many parts of the world to become naturalized. Like most ferns, it prefers to be kept moist. It is atypical in that it will tolerate a greater degree of sun than many ferns.
The Japanese Holly fern grows upright as a rounded mound. It can reach 2 to 3 ft (0.7 to 1 m) high and 3 ft (1 m) in width with leaves that can be greater than 1.5 ft (0.5 m) long. These glossy, dark green leaves are borne on arching stems. Each leaf is segmented with six to ten pairs of leaflets. The segments are known as pinnae. Individual leaflets have a leathery feel, teeth, come to a sharp point, and greatly resemble holly leaves.
This species of Cyrtomium keeps its leaves year round in areas that do not receive frost. It sheds them, however, in colder climates. This type of fern is hardy to 14° F (-10° C).
In the wild, the Japanese holly fern grows at lower altitudes. It grows in moist areas such as crevices in rocks, stream banks, and coastal cliffs. The plants are found widely throughout North America and Europe, in addition to their native Asia.
For cultivation, this type of Cyrtomium is one of the easier types of ferns to grow. In the United States, it has been a popular porch plant in the South since the 1800s. As a houseplant, it tolerates drafts, dry air, and low levels of light. The Japanese holly fern prefers bright light and soil that is kept continuously barely moist. This fern prefers household temperatures of 50° to 55° F (10° to 12.8° C) at night and 68° to 72° F (15.6° to 20° C) during the day.
Plants that are established should receive half-strength fertilizer at six month intervals. Overcrowded plants should be re-potted in the early spring. Two tablespoons (about 30 grams) of bone meal should be added to 1 gallon (3.8 liters) of soil mixture.
As a garden plant, this popular Cyrtomium species is a good addition to a shady bed of ferns or hostas and Caladiums. The Japanese holly fern prefers acidic, rich soil that drains well. It should be fertilized occasionally with standard fertilizer or fish emulsion. If the fronds become ugly, they can be cut back and will re-grow, as long as the crown is not damaged.