PLNTversePLNTverse
Plants › Ferns

Boston swordfern (Nephrolepis exaltata)

Nephrolepis exaltata is a terrestrial, evergreen perennial fern with rhizomes and creeping runners that can form clumps. Boston-type cultivars have gracefully drooping or arching fronds suited to hanging containers.

LightProvide bright indirect light to bright partial shade and avoid strong direct sunlight; indoors during winter, sunlight filtered through glass can be provided.
WaterDuring the growing season, keep the medium evenly moist but well drained, avoiding both complete drying and prolonged waterlogging; in winter, reduce watering and water again after the medium begins to dry.
HumidityNephrolepis exaltata prefers high humidity and has a high humidity need. It is generally reported to need moderate airflow.
TemperatureThe ideal temperature is 15–25 °C, with a maximum of 25 °C. Limited sources differ on the minimum temperature, which is about 5 °C. It is tender, and hardiness guidance describes it as suitable for relatively warm condit
Track your Boston swordfern in the PLNTverse app
Boston swordfern illustration

Overview

Nephrolepis exaltata is a terrestrial, evergreen perennial fern with rhizomes and creeping runners that can form clumps. Boston-type cultivars have gracefully drooping or arching fronds suited to hanging containers.

Origin and habitat

Sources differ on the native range: its core distribution is described as tropical to subtropical parts of the Americas, including Florida, Mexico, Central America, the Caribbean, and South America, while some sources additionally include Africa, Oceania, Polynesia, or tropical parts of Asia. It occurs in moist, shaded habitats, including moist forests, swamps, and floodplains, and may grow terrestrially or as an epiphyte, with growth on rocks less common. It is primarily adapted to warm, humid tropical to subtropical environments.

Characteristics

Sources differ on mature height, placing it at about 40–100 cm. According to limited source evidence, mature spread is about 100–150 cm. The fronds are pinnately compound; those of 'Bostoniensis' are long and drooping or arching, while the species has linear-lanceolate to narrowly elongated pinnae, with sources differing on frond dimensions. It is reported to have an erect rhizome.

Light

Provide bright indirect light to bright partial shade and avoid strong direct sunlight; indoors during winter, sunlight filtered through glass can be provided.

Watering

During the growing season, keep the medium evenly moist but well drained, avoiding both complete drying and prolonged waterlogging; in winter, reduce watering and water again after the medium begins to dry.

Humidity and airflow

Nephrolepis exaltata prefers high humidity and has a high humidity need. It is generally reported to need moderate airflow.

Temperature and dormancy

The ideal temperature is 15–25 °C, with a maximum of 25 °C. Limited sources differ on the minimum temperature, which is about 5 °C. It is tender, and hardiness guidance describes it as suitable for relatively warm conditions, with colder areas generally treating it as an indoor plant.

Growing medium and mounting

Use a humus-rich or nutrient-rich medium that is loose, aerated, and well drained; loamy or sandy media and acidic to neutral conditions are suitable.

Feeding

Fertilizer may be applied regularly during the growing season, although sources recommend differing schedules and fertilizer types, including balanced liquid, slow-release, and fast-acting liquid fertilizers.

Propagation

Propagation can be by division or by separating rooted plantlets formed on creeping runners; the species can also be propagated by spore, but Boston ferns are reported mostly not to produce spores, giving stronger source support to vegetative propagation for cultivars. Sources also describe the species as capable of forming spores on the undersides of the fronds. Division can be used for propagation, with source guidance calling for removing some potting medium and thinning some fronds during the process.

Common problems

Possible pests include scale insects and slugs; other sources also list Florida fern caterpillar and fern scale insect. Anthracnose may occur, and fronds may rot when they remain wet for prolonged periods. Allowing the potting medium to dry completely may impair growth, while overwatering can cause root rot; prolonged wetness can also rot fronds, and overhead summer watering is reported to cause frond damage under persistently damp conditions. It has weak cold tolerance and favors warm conditions; frost can make the above-ground fronds appear completely dead, and in cold regions it is best moved indoors for winter.

Identification

Key ornamental features are long, flexible, arching fronds, with pinnae arranged on both sides of the rachis and nearly round sori on the undersides of the fronds. Creeping stems and the absence of tubers are also described as features distinguishing it from some similar Nephrolepis ferns.

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