Ferns

By Tools for Gardeners

Planting ferns

Plant hardy ferns in spring or early fall into soil loosened with compost, with the crown right at the surface; burying it rots the plant. Most go in as nursery crowns or divisions, since raising ferns from spores is a multi-year project. Ferns belong in shade, under trees, along north walls, and in the beds where grass and flowers give up. Be honest about the site: nearly all want part to full shade and soil that stays lightly moist. A few, like cinnamon and southern shield ferns, tolerate sun, and only where water never runs short.

Planting details

• Plant in spring or early fall with the crown at soil level
• Spacing: 1 to 3 feet depending on mature spread
• Work in compost or leaf mold; ferns want organic, moisture-retentive soil
• Divide clumps by cutting through the rhizome, easiest in spring
• Boston fern is the porch standard but hardy outdoors only in zones 9 to 11

Growing requirements

Part shade to full shade suits most ferns; a wooded edge or the north side of a building is ideal. The soil should be loose, rich in organic matter, and slightly acidic to neutral, roughly pH 5.0 to 6.5, holding moisture like a wrung sponge rather than mud. Plan on an inch of water a week through the growing season where rain falls short, and keep a leafy mulch over the roots. Ferns are slow: a 2 gallon plant may need three or four years to look like the photo that sold it.

Harvesting and care

Deciduous types like ostrich and lady fern collapse with frost; rake the dead fronds off in early spring before new fiddleheads push. Evergreen types like Christmas fern get the same cleanup of winter-battered fronds. Divide crowded clumps in spring with a spade through the rhizome. Porch ferns come indoors before frost, where they want bright indirect light and as much humidity as you can offer. Ferns are famously unbothered by deer and rarely troubled by pests.

Common mistakes

• Planting in sun or dry soil, which crisps the fronds by midsummer
• Burying the crown, which rots the plant at the center
• Expecting fast coverage; most ferns need years to reach mature size
• Treating Boston fern as a hardy perennial north of zone 9
• Skipping summer water; an inch a week keeps fronds standing

Companion plants

Ferns are the connective tissue of a shade garden, filling gaps between hostas, astilbes, hellebores, and coral bells with fine texture the big leaves cannot match. Aggressive spreaders like ostrich fern pair better with equally assertive neighbors or a root barrier, while clump-formers like autumn fern sit politely anywhere. Keep all of them out of the sunny perennial border, where they will not survive the season.

• Hostas
• Impatiens

Varieties worth growing

• Boston fern: the arching porch and houseplant classic; outdoors only in zones 9 to 11
• Ostrich fern: tall vase-shaped native to 4 feet or more; spreads hard, so give it room
• Autumn fern: coppery new fronds that hold color; nearly evergreen in mild winters
• Christmas fern: dependable evergreen native for deep shade
• Lady fern: delicate fine-textured fronds; tolerates drier shade than most

Frequently asked questions

Sources

• Clemson Cooperative Extension HGIC: Hardy Ferns
• University of Wisconsin Extension Horticulture: Boston Fern