Adiantum aleuticum, western maidenhair fern
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Ferns

Adiantum aleuticum

western maidenhair fern

PteridaceaeWestern North America

At a Glance

TypeFern
HabitClumping
FoliageDeciduous
Height6-30 inches (15-76 cm)
Width12-24 inches (30-61 cm)
Maturity3 years

Growing Zones

USDA Hardiness Zones

3 - 9
Zone 3
Zone 4
Zone 5
Zone 6
Zone 7
Zone 8
Zone 9
These zones indicate the coldest temperatures this plant can typically survive.
Frost Tolerancehardy

Key Features

Deer Resistant
Container Friendly
Native to North America
Maintenancelow

Overview

Adiantum aleuticum is a deciduous clump-forming fern in the Pteridaceae family, growing 6-30 inches (15-76 cm) tall with a spread of 12-24 inches (30-61 cm). Fronds emerge from creeping rhizomes, each held on a glossy, dark brown to black wiry stipe that branches at the apex into a palmate or fan-shaped arrangement. The rachis divides into two main sections that spread in a horseshoe or semicircular pattern, creating a horizontal frond plane. Individual pinnules (leaflets) are fan-shaped, delicate, bright to medium green, and measure 0.5-1 inch (1.3-2.5 cm) across, with toothed to lobed margins. Water beads and rolls off pinnule surfaces without wetting them. Sori appear as brown patches protected by the reflexed pinnule margin rather than on the undersurface. New fronds emerge in spring with a delicate pinkish to pale green coppery flush. Colonies spread slowly; a single rhizome may expand 6-8 inches (15-20 cm) per year under favorable conditions. Foliage is frost-sensitive and browns after the first hard freeze; plants re-emerge from rhizomes in early spring.

Native Range

Native to western North America from the Aleutian Islands and southern Alaska south through British Columbia, Washington, Oregon, and California to northern Baja California, Mexico. Also found inland in Idaho, Montana, and scattered locations in the Rocky Mountains. Occurs in moist, shaded sites including forest understories, streambanks, rocky seeps, cliff faces, and talus slopes, from sea level to 11,000 feet (3,350 m) elevation. Tolerates serpentine and ultramafic rock substrates.

Suggested Uses

Planted in shaded woodland gardens, native plant landscapes, and along shaded streambanks where consistent moisture is available. Space 12-18 inches (30-46 cm) apart for groundcover effect in moist shade; colonies slowly expand to fill gaps within 3-4 years. Effective on slopes with seeps or constant moisture where shallow roots can stabilize soil. Suitable for containers with consistent watering and at least partial shade.

How to Identify

Identified by fan-shaped fronds on glossy, dark brown to black wiry stipes with a palmate branching pattern where the frond divides into two main sections spreading in a horseshoe arrangement. Fan-shaped pinnules, 0.5-1 inch (1.3-2.5 cm) across, are bright to medium green on black stems. Water beads and rolls off pinnule surfaces. Sori appear as brown dots along curled-under pinnule margins. Distinguished from Adiantum pedatum (eastern maidenhair fern) by its western range and tolerance for serpentine soils; the two species are closely related and visually similar.

Appearance

Size & Dimensions

Height6" - 2'6"
Width/Spread1' - 2'

Reaches mature size in approximately 3 years

Colors

Foliage Colors

green

Fall Foliage Colors

brown

Bloom Information

Adiantum aleuticum is a fern and does not produce flowers or bloom. Spores are produced in sori along pinnule margins, maturing from midsummer through fall.

Detailed Descriptions

Foliage Description

Bright to medium green fronds on glossy dark brown to black wiry stipes

Growing Conditions

Sun Requirements

Partial Shade
Full Shade
Tolerates up to 3 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.0(Neutral)
357912
Soil Types
loamrocky
Drainage
moist

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Time to Maturity

2-3 years

Care & Maintenance

Care Guide

Requires consistent moisture throughout the growing season; water deeply once or twice weekly in the absence of rain, providing 1-2 inches (2.5-5 cm) per watering during establishment. Even once established, dry periods exceeding 10-14 days cause frond browning and premature die-back. Maintain 2-4 inches (5-10 cm) of organic mulch (leaf mold, shredded bark) to retain soil moisture; keep mulch 2-3 inches (5-8 cm) away from the crown to prevent rot. Amend heavy clay soils with compost to improve drainage; standing water at the root zone causes crown rot. Performs in containers of at least 3 gallons (11 L) with consistent moisture. Leaf scorch occurs when exposed to direct afternoon sun for more than 1-2 hours; site accordingly.

Pruning

Cut dead or frost-damaged fronds to ground level in early to mid-spring (March-April in most zones) before new growth emerges. Fronds left standing over winter break down readily in spring and can be left as natural mulch. Remove fronds that brown prematurely during the growing season due to drought or mechanical damage, cutting at the base where the stipe meets the rhizome. Thin crowded colonies by removing the oldest central fronds in spring if fronds overlap excessively to improve air circulation.

Pruning Schedule

J
F
M
A
M
J
J
A
S
O
N
D
early spring

Maintenance Level

low

Container Growing

✓ Suitable for container growing

Minimum container size: 3 gallons

⚠️ Toxicity Warning

Non-toxic