Blechnum is a large and diverse genus of ferns in the family Blechnaceae. The species vary greatly. Some are small, cold-hardy forest plants that grow as far north as Iceland and Norway. Others are tropical tree ferns that are grown as ornamental plants indoors, or as garden plants in warmer climates. All types of blechnum ferns prefer to be kept moist.
The deer fern or hard fern, Blechnum spicant, grows from forests in northern California up to Iceland. It grows to be 1-3 ft (0.3-0.9 m) tall and can form a 3 ft (0.9 m) wide clump rising from a woody rhizome. This fern produces two types of leaves, depending on whether they are sterile or fertile. The outer sterile leaves have a wavy edge with 0.2-0.3 in (5-8 mm) leaflets. They surround the fertile leaves that are more narrow and erect.
This fern is frequently found growing in dense shade on decomposing conifers. It is grown in gardens as an evergreen ground cover. The plant prefers shade, along with some moisture. If it receives more sun, it requires more water.
One gallon (3.8 l) containers of deer fern should be spaced 3 ft (0.9 m) apart. If planted in a region that receives rain in the fall, they should not require much care. The plants may need to be watered during the first summer after having been planted.
These garden plants are propagated by spores, or by division of the clumps, in the spring or fall. It can take one to three months for the spores to germinate. The small plants should be transplanted into pots once they start producing fronds. The young ferns should be kept inside over the winter and then planted in the garden by early summer.
Another widely grown species is the miniature tree fern, Blechnum gibbum, that is usually grown as a houseplant or outside in subtropical or tropical climates. This dwarf tree fern grows to be 3-4 ft (0.9-1.2 m) high with fronds 2-3 ft (0.6-0.9 m) long. The fern prefers acidic soil and must be kept constantly moist for it to survive. As houseplants, it tolerates dry air better than many other types of ferns.
The miniature tree fern has been reported to survive temperatures down to 25°F (-3.8°C). If frozen, it will sometimes re-grow. In the continental United States, this fern is typically grown in gardens in the deep South, such as in parts of Florida, Louisiana, Texas, and southern California.
