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Boston swordfern (Nephrolepis exaltata)

Nephrolepis exaltata is an evergreen, clumping perennial fern that can grow terrestrially or as an epiphyte, with rhizomes, runners, and sword-shaped to lance-shaped fronds.

LightIt is generally reported to grow in bright indirect light to partial shade, avoiding strong direct sun during hot periods while tolerating some shade.
WaterDuring active growth, keep the growing medium moist but well drained, avoiding waterlogging and not allowing the potting medium to dry completely; reduce watering in winter. It is also generally described with a target t
HumidityFew sources report a preferred humidity of about 60–70 %. It is generally described as preferring high humidity and having a high humidity need. It is generally reported to need moderate airflow.
TemperatureSources differ, with limited evidence suggesting a minimum of about 10 °C. Sources differ on the ideal temperature, reported at about 15–25 °C. It is frost tender and is generally described as tender.
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Boston swordfern illustration

Overview

Nephrolepis exaltata is an evergreen, clumping perennial fern that can grow terrestrially or as an epiphyte, with rhizomes, runners, and sword-shaped to lance-shaped fronds.

Origin and habitat

Its main native range is described as tropical and subtropical America, including Florida, Mexico, Central America, the Caribbean, and South America, although sources differ, with some databases and literature also listing Africa, Asia, Oceania, or Pacific islands as native or part of its global distribution. It occurs in moist, shaded forests, swamps, and floodplains, growing terrestrially or as an epiphyte, with records from low to middle elevations. Its climate is tropical to subtropical, warm, and generally humid.

Characteristics

Few sources report a mature height of about 61–91 cm. Few sources report a mature spread of about 61–122 cm. The pinnately compound fronds are narrow and elongated, ranging from linear to lance-shaped, with narrow pinnae arranged along the rachis; frond posture among cultivars can range from upright to arching or drooping.

Light

It is generally reported to grow in bright indirect light to partial shade, avoiding strong direct sun during hot periods while tolerating some shade.

Watering

During active growth, keep the growing medium moist but well drained, avoiding waterlogging and not allowing the potting medium to dry completely; reduce watering in winter. It is also generally described with a target to keep slightly dry.

Humidity and airflow

Few sources report a preferred humidity of about 60–70 %. It is generally described as preferring high humidity and having a high humidity need. It is generally reported to need moderate airflow.

Temperature and dormancy

Sources differ, with limited evidence suggesting a minimum of about 10 °C. Sources differ on the ideal temperature, reported at about 15–25 °C. It is frost tender and is generally described as tender.

Growing medium and mounting

Use a humus-rich, fertile, loose, well-drained growing medium; loamy or sandy media are suitable, with neutral to slightly acidic or acidic to neutral conditions.

Feeding

During spring and summer growth, diluted balanced fertilizer can be applied monthly; sources for Nephrolepis exaltata also recommend regular liquid or slow-release fertilizer during the growing season.

Propagation

It can be propagated by division or by separating rooted plantlets formed on runners, and the species can also be propagated from mature spores.

Common problems

Scale insects, slugs, and fern caterpillars may cause damage. Overly wet growing medium can cause root rot, and persistently wet foliage may also rot. Overwatering and poor drainage may lead to root rot, insufficient water can cause the plant to decline, and strong direct light may scorch the fronds. It has little tolerance for cold; in cold regions it is recommended to move it indoors in winter, and frost may kill the above-ground fronds.

Identification

Nephrolepis exaltata has rhizomes and runners and is generally reported not to form the swollen tubers or water-storage roots characteristic of N. cordifolia; round sori can form on the undersides of the fronds.

Photos

Nephrolepis exaltata
📷 unknown · CC BY-SA 3.0 · source
Nephrolepis exaltata
📷 Thomas Irvine, some rights reserved (CC BY), uploaded by Tho · CC BY · source

Sources