The Boston Fern (Nephrolepis exaltata) is an herbaceous plant with ornamental foliage highly valued worldwide. Widely cultivated as an indoor plant and on shaded balconies since the Victorian era, it stands out for its ability to transform spaces with its dense texture and lush appearance. Its long, curved fronds, with delicate and slightly serrated leaflets, have a look that is at once light, elegant, and voluminous, ideal for hanging in suspended baskets or placing on tables and countertops. Over the past few decades, the Boston Fern has established itself as one of the most popular and readily available ornamental plant species in supermarkets, florists, and garden centers.
Its hardiness, coupled with its rapid growth and adaptation to partial shade and humid environments, makes this fern a safe choice for both novice and experienced gardeners. With a wide variety of cultivars, the species shows considerable variations in size, texture, density of fronds, and environmental tolerance. Among the most appreciated cultivars is the ‘Bostoniensis’, with gently arched fronds and a “feathery” appearance, a true classic in interior decoration.
In addition to its beauty, the Nephrolepis exaltata adds functional value to the spaces where it is grown. NASA studies demonstrate its effectiveness as an air purifier, removing pollutants such as formaldehyde, xylene, and toluene, and increasing the relative humidity of the air in enclosed spaces, making it ideal for places like living rooms, offices, bathrooms, and kitchens. Its non-toxicity to humans and animals also contributes to its wide acceptance in homes with children and pets.
Native to tropical and subtropical regions of the Americas, the Boston Fern naturally occurs in humid and swampy forests of Mexico, Central America, South America, as well as the Caribbean and Polynesian islands. It is a species that can grow both as a terrestrial plant and as an epiphyte, especially on palm trunks like the Sabal palmetto, in environments with closed canopy, high relative humidity, and diffuse light.
The genus name, Nephrolepis, derives from the Greek “nephros” (kidney) and “lepis” (scale), in reference to the shape of the protective structures covering the sporangia, known as indusia, found on the fertile fronds. These kidney-shaped structures are a key feature for identifying the genus. The specific epithet “exaltata” comes from Latin and means “elevated” or “to raise,” possibly alluding to the plant’s stature and the upright arrangement of the fronds during early growth stages, or as a tribute to its ornamental appearance.
Nephrolepis exaltata is a perennial, rhizomatous plant with a growth habit ranging from sub-erect to pendulous and a herbaceous texture. The plant develops in dense, voluminous clumps originating from a slender, elongated underground rhizome with scaly, slightly tuberous branches. This inconspicuous rhizome plays a crucial role in vegetative propagation by producing stolons that generate new plants under favorable environmental conditions.
The rhizome has a herbaceous consistency and a light brown color, covered with basal scales that protect the growth meristems. From it emerge the fronds—compound leaves with a rigid central axis known as the rachis—which in commercial cultivars can reach between 8 and 59 inches (20 and 150 cm) in length, and up to 98 inches (250 cm) in wild specimens. Frond growth starts upright, later arching as they age, giving the species its characteristic ornamental form. The fronds have a soft and light texture, with a pale to medium green coloration and a delicate appearance.
The fronds of the American sword fern are pinnate, with alternately arranged pinnae (leaflets) along the rachis. Each pinna ranges from 1.2 to 3.1 inches (3 to 8 cm) in length and about 0.2 to 0.4 inches (0.5 to 1 cm) in width, with a linear-lanceolate to oblong-lanceolate shape. The margins vary from entire to slightly serrated, with a smooth, matte adaxial surface and an abaxial surface often covered with mature sori during the fertile stage.
The arrangement of the pinnae gives the frond a feather-like appearance, with a light and airy texture. Young fronds are semi-erect, more compact and shorter, while mature fronds become recurved and pendulous. The leaf structure does not exhibit secondary branching, although some cultivars display bipinnate fronds and various morphologies such as wavy, spiral, or overlapping fronds, resulting from horticultural selection.
Nephrolepis exaltata reproduces through spores (asexual phase), which are formed in sporangia organized into sori. These sori are rounded in shape, located near the edges on the underside of the pinnae, usually arranged in two lateral rows parallel to the central vein of each leaflet. The sporangia are protected by a structure called an indusium, which is kidney-shaped, a form that justifies the name of the genus.
Under ideal environmental conditions, the spores germinate to produce prothalli, gametophytic structures that will give rise to new plants through gametic fertilization (sexual phase). This process is dependent on the presence of water, as the mobile antherozoids require a liquid film to reach the archegonia. Pollination, as known in flowering plants, does not occur in pteridophytes, being replaced by gametogamy, a mechanism characteristic of the group.
The sporulation of Nephrolepis exaltata can occur almost year-round in tropical regions, with greater intensity in spring and summer, when the relative humidity of the air is higher. When cultivated at home, spore formation is less frequent due to the genetic manipulation of the ornamental cultivars we use, and to environmental conditions, which do not always favor the complete reproductive cycle of the plant.
Currently, two botanical subspecies within the species Nephrolepis exaltata are recognized. The first, Nephrolepis exaltata subsp. exaltata, is widely distributed throughout the tropical and subtropical regions of the Americas, ranging from the southern United States to South America. The subspecies Nephrolepis exaltata subsp. hawaiiensis is endemic to the Hawaiian Islands, occurring exclusively in this Pacific archipelago.
The history of the popularization of Nephrolepis exaltata is closely related to the development of the cultivar ‘Bostoniensis’, which remains the most popular cultivar of the species to this day. Its origin dates back to the late 19th century, in a context where ferns were experiencing a peak in interior decoration during the Victorian Era. In 1894, the nurseryman F. C. Becker, from Cambridge, Massachusetts, received a shipment of about two hundred plants of the species Nephrolepis exaltata, sent from a nursery in Philadelphia.
Among them, Becker noticed a unique plant that grew more rapidly, had larger fronds, and displayed an unusual hanging habit, contrasting with the upright stature typical of the species. Upon propagating this plant, it was recognized as a spontaneous mutation, and in 1896, botanists in London formally identified this new form and suggested the name ‘Bostoniensis’, in reference to the city of Boston.
Since then, ‘Bostoniensis’ has become a true icon in landscaping and interior decoration, especially in the United States and later in various tropical and subtropical regions around the world. Such was its demand and popularity, the ‘Bostoniensis’ cultivar was the first ornamental foliage to be commercially propagated via tissue culture, according to Hartman and Zettler (1986), an important milestone for the ornamental plant market.
Following this advancement, numerous other cultivars of Nephrolepis exaltata were developed through somaclonal variants, that is, spontaneous mutations induced or observed during in vitro multiplication, many of which were directly derived from ‘Bostoniensis’ lineages. This variety not only boosted the dissemination of the species as an indoor plant, giving rise to many types of Boston Fern, but also paved the way for the genetic and commercial exploration of other ornamental species and varieties.
Other notable cultivars of Nephrolepis exaltata include:
- ‘Dallas’: A compact variety that tolerates lower levels of light and humidity, ideal for indoor environments with indirect lighting.
- ‘Fluffy Ruffles’: Features smaller fronds with dense leaflets and wavy edges, providing a delicate and ornamental texture.
- ‘Golden Boston’: Stands out for its fronds of yellow-greenish coloration, providing a vibrant contrast in landscape compositions.
- ‘Rita’s Gold’: Has compact fronds of chartreuse hue, being an attractive option for well-lit indoor environments.
- ‘Compacta’: This variety has a reduced size and short, dense fronds, with leaflets arranged closer to the central axis. It is ideal for small spaces, smaller pots, and environments with less light availability.
- ‘Massii’: Similar to ‘Bostoniensis’, but with fronds of a darker green color and a more pendant growth habit.
- ‘Florida Ruffle’: Characterized by medium-sized fronds with doubly divided leaflets, giving a more feathery and dense appearance.
- ‘Fluffy Duffy’: A small-sized variety with finely divided fronds, resulting in a plant with a dense and delicate appearance.
- ‘Whitmanii’: Features extremely cut fronds, with thin, intertwined leaflets that form an almost filigree structure.
- ‘Rooseveltii’: Features finely cut fronds with crested ends, offering a unique and ornamental texture.
- ‘Verona’: A traditional cultivar with very pendant fronds and a lacy appearance, ideal for hanging baskets.
- ‘Tiger Stripe’: This cultivar draws attention with its variegated pattern on the fronds, with irregular stripes of dark green and light green along the leaflets.
- ‘Elegantissima’: A cultivar with bipinnate fronds, very delicate in appearance and awarded by the RHS (Royal Horticultural Society).
The Boston Fern and its numerous cultivars have secured their position as one of the most versatile and popular ornamental foliage in contemporary landscaping. Its arched and elegant fronds create a lush, tropical look that adapts perfectly to both indoor and outdoor environments. In both residential and commercial landscaping, the Boston Fern is often used as both a focal point and a backdrop in shaded flower beds, where its vibrant green fronds beautifully contrast with darker foliage plants or colorful flowers.
From the Victorian era to the current and growing Urban Jungle movement, the Boston Fern delights gardeners and enthusiasts alike, playing a key role in creating environments that reconnect people with nature, contributing to the creation of biophilic and appealing settings. Its ornamental benefits include the ability to soften rigid architectural lines and add texture and dynamism to indoor spaces. In urban apartments and offices, it is used in hanging pots, shelves, and elevated stands, where its cascading fronds create natural green curtains that transform impersonal spaces into welcoming havens.
The versatility of the Boston Fern shines especially in vertical gardens, where it adapts well to both indoor and outdoor structures. In tropical and subtropical climates, it forms stunning compositions on living walls and green facades, while in temperate climates it finds its ideal place in winter gardens, humid greenhouses, and other protected areas. Its ability to thrive in different levels of indirect light makes it a safe choice for landscapers and decorators working with shaded spaces, from urban internal patios to understories in rural properties, where it can integrate as ground cover.
The Boston Fern prefers environments with partial shade, abundant diffuse or indirect light, similar to the filtered lighting under the canopy of tropical forests. Direct sunlight exposure, especially during the hottest parts of the day, can cause burns on the fronds, leading to yellowing and drying of their tips. In regions with subtropical or temperate climates, it is best to choose locations near windows with light curtains or on protected balconies, always avoiding hot or cold air drafts or large seasonal temperature variations. In tropical or equatorial locations, they can be in open, well-ventilated environments, provided that the air humidity is naturally high.
Like the vast majority of ferns, the Boston Fern prefers locations with high relative humidity (over 50%), temperatures between 64°F (18°C) and 82°F (28°C), and good ventilation. Although it can tolerate slightly lower temperatures for short periods, prolonged exposure to temperatures below 50°F (10°C) can seriously compromise its growth, leading to frond drop and, in extreme cases, plant death. The species does not tolerate frost and should be protected during the winter in temperate climate regions, with indoor cultivation recommended in these cases. One should resist the temptation to move the plant outdoors annually in the summer, as despite improving its growth and performance, it will perish with the move back indoors during the winter.
The substrate for this species requires good moisture retention but must also allow excellent drainage. The ideal mix should consist of an organic substrate rich in decomposed plant matter and highly fibrous, such as peat, aged pine bark, and coconut fiber, with the addition of perlite or coarse sand to improve drainage. The ideal pH is between 5.5 and 6.5. Pots with drainage holes are essential to avoid permanent waterlogging and ensure good aeration in the substrate.
Planting the Boston Fern should be done carefully to avoid damaging the rhizomes and fine roots. The planting depth should allow the base of the fronds to be level with the rim of the pot, ensuring aeration and preventing moisture accumulation at the leaf insertion point. In hanging pots, it is necessary to ensure that the container can support the weight of the plant and watering. After planting, watering should be ample, moistening the entire potting mix and keeping it consistently moist without waterlogging.
Watering should be frequent, especially during the warmer months, and it is advisable to water the Boston Fern whenever the surface of the potting mix begins to dry out. In indoor environments with low relative humidity, it is beneficial to supplement watering with periodic misting of the fronds or even using an electric humidifier.
During winter, the frequency of watering should be reduced, respecting the slower growth rate of the plant. Fertilization should be carried out biweekly during the growing season (spring-summer), preferably with liquid fertilizers high in nitrogen, which promote leaf growth and intense green coloration. Foliar fertilizers are particularly effective for these ferns.
The Boston Fern can benefit from regular cleanings, consisting of removing dry, yellowed, or damaged fronds and an occasional rain shower or gentle hose-down. This toilet practice stimulates the emergence of new shoots, removes dust, and enhances the beauty of the specimen. General maintenance includes partial and periodic replacement of the potting mix (every two years), cleaning the leaves with a damp cloth or water sprays, and repotting into larger pots as the clump grows. However, avoid using pots that are too large, which may hinder plant management. When the specimen becomes too large, it is more convenient to divide the clump rather than planting it in an even larger pot.
The resilience of the Nephrolepis exaltata to weather conditions is moderate. It does not tolerate strong winds well, which can tear its delicate fronds, nor does it adapt to coastal environments with constant salty breezes. It also does not tolerate prolonged drought, requiring frequent watering to maintain its good health. Although it has some hardiness, it is sensitive to sudden temperature changes, frosts, and prolonged periods of low relative humidity, conditions that induce leaf dehydration and collapse of the root system.
The plant has low attractiveness to deer and rabbits, making it suitable for protected gardens in rural areas. However, it is susceptible to some common pests in humid and shaded environments, such as scale insects, aphids, slugs, snails, caterpillars, and whiteflies. Under low humidity conditions, particularly in indoor environments with air conditioning, problems with mites and darkening of the tips of the fronds may occur. Prevention consists of maintaining adequate humidity, periodic inspection of the fronds, and the application of specific phytosanitary products when necessary, such as mineral oils or botanical extracts.
Propagation of the Boston Fern by division of clumps is the most efficient and widely used method. Division should preferably be carried out at the end of winter or the beginning of spring, when the plant starts to produce new shoots. The procedure involves removing the plant from the pot, followed by careful separation of the clump, avoiding breaking up the root balls, into segments that contain well-developed fronds, rhizomes, and roots. Each segment should be replanted in an individual container, using fresh potting mix and maintaining high humidity in the first weeks to facilitate rooting and acclimatization. The use of humid greenhouses or protected environments is highly recommended at this stage, providing stable temperature, good ventilation, and adequate light.
