Growing Temperatures for Ferns

Zones 2 to 3

• Only the cold-hardiness ferns tolerate the icy winters in USDA zones 2, which reaches lows of minus 50 degrees and zone 3, which reaches minus 40. Ferns hardy to zone 2 include the sensitive fern (Onoclea sensibilis), which is hardy in zones 2 to 10 and grows to 3 feet tall. This deciduous fern has broad foliage that turns bronze in autumn. Zone 3 ferns include the glade fern (Athyrium pycnocarpon), with its 3-foot-long, arching fronds, and the Northern maidenhair (Adiantum pedatum), with its airy, blue-green foliage. Both are hardy in zones 3 to 8.

Zones 4 to 5

• USDA zones 4 and 5 experience average annual lows to minus 30 and minus 20 degrees. The marginal wood fern (Dryopteris marginalis) is hardy in zones 4 to 9. This evergreen grows to 2 feet tall and has tapering, blue-green fronds. Ferns hardy to zone 5 include the lowland brittle fern (Cystopteris protrusa), which grows to 18 inches tall and has deciduous, dissected foliage.

Zones 6 to 7

• USDA zone 6 experience annual lows to minus 10 degrees and zone 7 dips to 0 degrees. The 12-inch-tall tongue fern (Pyrrosia lingua) is hardy in zones 6 to 10. This evergreen has leathery, tapered, non-dissected foliage. The Indian holly fern (Arachniodes simplicior) is hardy in zones 7 to 9 and reaches 18 inches tall. This erect evergreen has wavy, dark fronds.

Zones 8 to 9

• In USDA zones 8 and 9, average lows dip to 10 and 20 degrees. The felt fern (Pyrrosia hastate) is hardy in zones 8 to 10 and grows to 14 inches tall. Like the tongue fern, this evergreen has non-dissected fronds. The bramble fern (Hypolepis repens) is hardy in zones 9 to 10. This large deciduous species grows to 8 feet tall. It has large, triangular fronds with very small leaflets.

Zone 10 to 11

• USDA zones 10 and 11 only reach average annual lows of 30 and 40 degrees. Ferns for these warm climates include the sickle fern (Pellaea falcate), an 18-inch-tall evergreen with erect fronds. Its foliage ranges from dull to glossy on the same plant. Sickle ferns are hardy in zones 10 and 11. The Australian tree fern (Sphaeropteris cooperi) is hardy in zones 10B to 11. This tropical plant grows from 15 to 30 feet tall and has a single, thick trunk-like stem. Its fronds grow up to 30 inches long.