Can you suggest a spreading, evergreen fern that would be suitable as a groundcover?
Unfortunately, there are very few fern species that are both spreading and evergreen. Two possibilities are:
Adiantum venustum (Himalayan maidenhair fern)-
This evergreen species may not stay green throughout the winter in Zone 5 but should be evergreen in warmer zones. Grows to 12 to 15 inches tall. It does not spread from spores but most plantings will expand with time. When propagating by division, use large sized divisions for best success. In early spring, new fronds emerge which are salmon-colored and very attractive.
Athyrium niponicum (Japanese painted fern)-
The cultivar 'Pictum' (also known as A. goeringianum 'Pictum') is a very popular fern in American gardens. It has beautiful tricolored fronds (burgandy, green and grey). It does well in a shady location and in facy produces better color in the shade. In loose soil it will spread and form a dense mass. Zones 4-9.
Blechnum penna-marina (little hard fern)-
This is a smaller species growing to 4 to 12 inches. Hardiness: zones 6 – 8. Prefers acidic, well-drained soils. Emerges as russet-colored fronds in the spring. Can be propagated easily by division.
There are numerous deciduous, clumping ferns that can be grown as a groundcover by planting them closer together. It is usually recommended that ferns be planted at a distance apart equal to the eventual height of the plant. By planting closer than this, good coverage can be achieved in three or four years. A good reference source should be consulted to choose the best species for a particular location.
Dropteris erythrosora (Autumn fern)
This a colorful fern with bronze fronds in the young plant. It can stay green all winter. It grows to a height of about 1.5 - 2 ft. Zones 5-8.
Four deciduous species that could be considered are:
Dennstaedtia punctilobula (hay-scented fern)-
This is a very aggressive species with soft, feathery fronds. Perhaps more suitable for wide-open spaces than a small garden, it reaches a height of 18 to 30 inches. Hardy in zones 3 - 8. Emits its characteristic odor when cut.
Gymnocarpium dryopteris (common oak fern)-
Not as vigorous as the hay-scented fern and not as tall. Height: 9 to 12 inches. Hardy in Zones: 2 - 8. Has very attractive fronds; the variety ‘Plumosum” is even better. It does not do well in hot summers.
Blechnum spicant (hard fern)-
This species has elegant, dark green, sterile fronds and a bunch of erect fertile fronds emanating from the center. Grows best in deep humus and prefers acidic soil. Hardy in Zones: 5 - 8.
Asplenium trichomanes (maidenhair spleenwort)-
We mention this species because it is short and suitable for rock gardens or at the front of a border. Height is only 4 to 8 inches. Hardy in Zones: 3 - 9.
J. Mickel. Ferns for American Gardens. Macmillan Publishing Co. 1994.
R. Steffen and S. Olsen. The Plant Lover’s Guide to Ferns. Timber Press. 2015
Courtesy of NYBG Plant Information Service