Maidenhair fern

About Maidenhair fern

Maidenhair ferns have airy, arching fronds of small fan-shaped leaflets on wiry, shiny black stems; the name Adiantum means 'unwetted', since water beads off the leaves (NC State). The delta maidenhair (A. raddianum) from tropical America and the West Indies is the usual houseplant, while the southern maidenhair (A. capillus-veneris) grows wild in warm regions around the world, including a few coastal spots in North Carolina, where it is listed as endangered. They are fussy indoors: UMN Extension calls them a real challenge, since they want greenhouse-like humidity and roots that never dry out.

The delta maidenhair is hardy outdoors only in zones 9b-10 and the southern maidenhair in zones 6-9 (NC State); as houseplants they are grown indoors everywhere and can summer outdoors in shade once nights stay above about 55 F.

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

Usually bought as a nursery plant or started by dividing the creeping rhizomes; ferns make spores, not flowers or seeds (NC State).

Growing it indoors

• Light: Medium light, such as an east window or a few feet from a south or west one, moved right up to a west or south window from November through February (UMN); full sun scorches it and deep shade weakens it (NC State).
• Water: Never let the roots dry out: keep the mix evenly moist (NC State, UMN), water until it drains and empty the tray after a few minutes. Use room-temperature water, not softened water, which builds up salts (UMN).
• Humidity: It needs high humidity, as in a bathroom or terrarium (NC State); UMN prefers a room humidifier to misting, which does little and can spread leaf spot.
• Temperature: MU Extension lists ferns at about 55 F nights; keep it away from hot, dry air near the ceiling or heat sources (UMN).
• Feeding: Ferns need little: feed only during active new growth with fish emulsion or a houseplant fertilizer at half strength, used sparingly, since overfeeding browns the frond tips (UMN); NC State notes potted southern maidenhair does need some feeding.
• Repotting: Move it to a larger pot of peat-rich mix when it outgrows its pot (UMN), dividing the clump at the same time if you like (NC State).

Soil

A highly organic, porous, peat-rich potting mix that holds moisture but drains (UMN, NC State); the southern maidenhair tolerates neutral to alkaline soil.

Pot in a highly organic, porous, peat-rich mix that holds moisture but drains (UMN, NC State).

Feeding

• During active new growth, or when the fronds look paler than normal: fish emulsion, or a houseplant fertilizer at half strength. Apply sparingly (UMN); NC State notes potted southern maidenhair does need some feeding.
• When it isn't putting out new fronds, such as in winter: none. Hold off until new growth starts (UMN).

Ferns are easily damaged by over-fertilizing, which browns the frond tips first (UMN).

Varieties (10)

NC State names 7 cultivars of the delta maidenhair and 3 of the southern maidenhair.

Pests to watch for

Mealybugs, Scale insects

Diseases and problems

Leaf sunburn, Brown frond tips (dry air, overfeeding)

In the kitchen

Safety: Neither NC State page lists it as poisonous or gives it a poison rating. Old herbals used it as a cough remedy (see history), which is not advice.

Pets: Not listed by the ASPCA.