Boston Fern (Nephrolepis): Cultivation and Care

botany

The Nephrolepis, better known as the Boston fern, belongs to the Nephrolepidaceae family or, according to some classifications, to the Dryopteridaceae family. Its scientific name comes from the Greek nephros, meaning “kidney,” and lepis, meaning “scale,” referring to the characteristic shape of its sori, the structures containing spores located on the underside of the fronds.

In its natural habitat, Nephrolepis thrives in tropical and subtropical climates, often in humid undergrowth or as an epiphyte on other plants. It is found in Central and South America, Southeast Asia, and Australia, where it enjoys a warm and humid atmosphere. Generally not hardy, it is cultivated indoors in places like conservatories, where its lovely foliage persists through winter. The genus includes around thirty species. Among the most commonly cultivated species are:

• Nephrolepis exaltata, the most widespread, with the famous ‘Boston’ variety prized for its gracefully arching fronds.
• Nephrolepis cordifolia, distinguished by its hardiness down to -8°C and a more compact habit.
• Nephrolepis obliterata, sometimes called the Kimberley fern, with stiffer fronds.

Nephrolepis obliterata Kimberley

Nephrolepis exaltata boasts a variety of cultivars, each with its unique charm:

• ‘Bostoniensis’: admired for its long, bright green fronds and generously trailing habit.
• ‘Green Lady’: known for its thicker, slightly undulate fronds, offering a lush and dense appearance.
• ‘Duffii’: features compact fronds with round, glossy leaves, ideal for those seeking a touch of originality.
• ‘Fluffy Ruffles’: famous for its highly divided and curly fronds, adding a unique and airy texture.
• ‘Teddy Junior’: a dwarf version with short, dense fronds, perfect for small spaces or terrariums.
• ‘Whitmanii’: displays wider, sturdier fronds with vigorous growth and a beautiful green colour.

Nephrolepis exaltata

Nephrolepis is a perennial fern that forms a dense, elegant clump with an upright habit, reaching about 50 cm in height. It spreads indefinitely thanks to its running rhizomatous system. In pots, its expansion will be contained.

The foliage stands out for its delicacy and elegance, composed of soft, elongated fronds, finely divided, giving the plant a light and airy habit. These fronds, measuring up to 50 cm long in mature plants, are typically arched and emerge from a thin yet sturdy central rachis. The pinnae, or leaflets, that make up each frond are inserted alternately or oppositely, depending on the species. They are narrow, lanceolate, and often slightly asymmetrical at their base. Their edges can be entire, finely crenate, or delicately undulate, enhancing the delicate appearance of the foliage. Each pinna is traversed by a prominent midrib, which structures the leaf and contributes to its flexibility. In Nephrolepis exaltata, the emblematic species of the genus, the fronds are particularly long and flexible, adopting a naturally trailing habit.

The foliage colour varies depending on growing conditions, ranging from bright green to deep green, sometimes tinged with slightly glaucous hues. The surface of the fronds is smooth and sometimes subtly glossy.

Like all ferns, Nephrolepis produces neither flowers nor fruits and reproduces by dispersing spores. These spores form under the fronds, grouped within structures called sori (or sores). In Nephrolepis, these sori are covered by membranous indusia, small protective scale-like structures that regulate spore release at ripeness.

Nephrolepis exaltata (© Forest and Kim Starr)

Appreciated for its dense and airy foliage, this fern is also valued indoors for its ability to humidify the air and absorb certain toxins present in the atmosphere, such as formaldehyde and xylene. It is therefore ideal for improving air quality in homes and apartments.

Main species and varieties

Nephrolepis cordifolia Artic Jungle - Boston Fern

The hardiest among this genus of ferns, it also adapts well indoors or in a conservatory.

• Höhe bei Reife 50 cm

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### Cultivating Nephrolepis Indoors Nephrolepis, commonly known as the Boston fern, is a popular choice for indoor gardening due to its lush, feathery fronds and relatively easy care requirements. Here’s how to successfully grow and maintain this elegant fern in your home. #### **Light Requirements** Nephrolepis thrives in bright, indirect light. Avoid direct sunlight, as it can scorch the delicate fronds. A north or east-facing window is ideal. If natural light is limited, consider using a grow light to supplement. #### **Watering** Keep the soil consistently moist but not waterlogged. Water when the top inch of soil feels dry to the touch. These ferns appreciate high humidity, so misting the leaves regularly or placing the pot on a tray of pebbles filled with water can help maintain moisture levels. #### **Temperature and Humidity** Nephrolepis prefers temperatures between 15-24°C (60-75°F). Avoid placing it near drafts, radiators, or air conditioning vents. High humidity is crucial—aim for levels above 50%. A humidifier can be beneficial in dry environments. #### **Soil and Fertilisation** Use a well-draining, peat-based potting mix. Feed the fern with a balanced liquid fertiliser diluted to half strength every 4-6 weeks during the growing season (spring and summer). Reduce feeding in autumn and winter. #### **Pruning and Maintenance** Remove yellow or brown fronds to encourage new growth and maintain the plant’s appearance. Regularly check for pests like spider mites or scale, and treat promptly if detected. #### **Repotting** Repot every 1-2 years in spring if the plant becomes root-bound. Choose a pot only slightly larger than the current one to prevent overwatering issues. By following these guidelines, your Nephrolepis will flourish indoors, adding a touch of greenery and elegance to your living space.

Where to Place a Boston Fern in the House?

The Nephrolepis thrives in bright, but indirect light. It should be placed in partial shade, ideally near an east or north-facing window. Direct sunlight may scorch its foliage, while insufficient light will make it less dense and vigorous. It prefers an ambient temperature between 18 and 24°C and cannot tolerate temperatures below 12°C. Humidity should be high, as dry air can cause the fronds to turn brown. To maintain good humidity levels, it is advisable to mist its foliage regularly or place the pot on a tray of damp clay pebbles.

When to Plant a Boston Fern in a Pot?

The Boston Fern can be planted year-round indoors, but spring is the ideal time to allow it to adapt well to its new environment.

How to Plant It in a Pot?

The choice of pot is important: it must have drainage holes at the bottom to ensure proper drainage. An unglazed terracotta pot is recommended, as it allows better evaporation of excess moisture. Its size should be slightly larger than the root ball, without being too big to prevent water from stagnating in overly voluminous soil.

Which Substrate to Choose?

The Nephrolepis requires a light, well-draining, and organic-rich substrate. A good mix can be made with equal parts of:

• Potting soil
• Turf or sphagnum moss, to retain moisture without suffocating the roots
• Perlite or sand, to improve drainage

Steps for Potting

1. Choose a pot with drainage holes to allow water to escape.
2. Place a drainage layer (2-3 cm of clay pebbles or gravel) at the bottom of the pot.
3. Partially fill the pot with the prepared substrate.
4. Place the root ball in the center of the pot without burying the base of the fronds.
5. Add substrate around the roots, lightly pressing it down.
6. Water moderately, moistening the substrate without soaking it.
7. Position the plant in its final spot, avoiding drafts and direct heat sources like radiators.

Nephrolepis cordifolia

Planting in a Terrarium

The Boston Fern is not ideal for a closed terrarium, but it can thrive very well in an open terrarium. This plant loves humidity but also needs good air circulation to prevent excess moisture, which could encourage mold growth or yellowing of its fronds.

In an open terrarium, it creates a stunning mini-jungle effect with its trailing foliage. Just ensure it has a well-draining substrate, composed of light potting soil mixed with perlite or coconut fiber, to prevent the roots from staying too wet. A thin layer of gravel or clay pebbles at the bottom of the container is recommended.

Cultivation and Care of the Boston Fern Indoors

The Nephrolepis, or Boston fern, is a robust plant, but it requires minimal attention to maintain dense and vibrant foliage. Its care mainly involves appropriate watering, regular fertilisation, sufficient ambient humidity, and periodic repotting.

Watering: How and How Often?

The Nephrolepis prefers a slightly moist substrate but never waterlogged. Watering should be regular and moderate to avoid root rot.

• During the growth period (spring-summer): water 2 to 3 times a week, allowing the surface of the substrate to dry slightly between waterings.
• In autumn and winter: reduce watering to once a week, or even less if the room is cool, while maintaining good ambient humidity.

The water used should be non-calcareous (preferably filtered, demineralised, or rainwater) and at room temperature to avoid thermal shock to the roots.

Misting

The Boston fern thrives in a humid environment: mist daily, especially in winter.

Fertilisation: When and How to Feed the Nephrolepis?

A nitrogen-rich liquid fertiliser is essential to maintain dense, lush green foliage.

• In spring and summer, add a liquid fertiliser for green plants every two weeks, diluted by half to avoid nutrient overload.
• In autumn and winter, space out applications to once a month, or even suspend fertilisation if growth slows.

Pruning: Should You Trim the Fronds?

The Nephrolepis does not require strict pruning, but it is advisable to regularly remove dry or yellowed fronds to stimulate the growth of new shoots and maintain a beautiful shape. A clean cut at the base with disinfected scissors is sufficient.

Repotting: When and How to Do It?

Repotting is necessary every 1 to 2 years, in spring, when the roots fill the pot or the fern appears cramped. Repotting can also be an opportunity to divide the clump and propagate the plant. A slightly larger pot than the previous one will ensure continuous growth without excess moisture.

• Choose a slightly larger pot with drainage holes.
• Use a light, well-draining substrate, composed of potting soil for green plants, turf, and perlite.
• Divide the plant if it is too large, carefully separating the rootstocks to obtain several new young plants.
• Water lightly after repotting and maintain good ambient humidity to aid adaptation.

### Parasites and Diseases of the Nephrolepis The *Nephrolepis*, commonly known as the Boston fern, is a popular ornamental plant prized for its lush, feathery fronds. However, like all plants, it can fall victim to various **parasitic** pests and diseases. Here’s a guide to identifying and managing these issues to keep your fern healthy and thriving. #### Common **Parasitic** Pests: 1. **Spider Mites** (*Tetranychus urticae*): These tiny arachnids suck sap from the leaves, causing yellow speckling and webbing. **Solution**: Increase humidity and use insecticidal soap or neem oil. 2. **Mealybugs** (*Pseudococcidae*): White, cottony masses on the fronds indicate their presence. They weaken the plant by feeding on its juices. **Solution**: Remove manually with a cotton swab dipped in alcohol or apply horticultural oil. 3. **Scale Insects** (*Coccoidea*): These appear as small, brown bumps on the fronds or stems. They excrete honeydew, leading to sooty mould. **Solution**: Scrape off gently or treat with insecticidal soap. #### Common Diseases: 1. **Root Rot** (*Pythium* or *Phytophthora* spp.): Overwatering leads to soggy roots, which turn brown and mushy. **Solution**: Improve drainage and reduce watering. Remove affected roots and repot in fresh soil. 2. **Leaf Spot** (*Cercospora* or *Alternaria* spp.): Brown or black spots with yellow halos appear on the fronds. **Solution**: Remove infected leaves and avoid overhead watering. Apply a fungicide if necessary. 3. **Powdery Mildew** (*Erysiphe* spp.): A white, powdery coating on the leaves indicates this fungal infection. **Solution**: Improve air circulation and treat with a fungicide. #### Preventive Measures: - Ensure proper humidity and avoid overwatering. - Inspect new plants before introducing them to your collection. - Keep the foliage clean by occasionally wiping the fronds with a damp cloth. By staying vigilant and addressing issues promptly, you can enjoy a vibrant and healthy *Nephrolepis* in your home or garden.

The Nephrolepis is a relatively hardy plant, but unsuitable growing conditions can encourage the appearance of parasitic pests and diseases. Excess moisture, overly dry air, or poor ventilation can weaken the plant and make it more vulnerable.

Common Parasitic Pests

•  Mealybugs: These small, white, cottony insects attach themselves to the stems and undersides of the fronds, causing the plant to weaken. You can remove them with a cotton pad soaked in 70% alcohol or by spraying a mixture of water and black soap.
• Aphids : They sometimes attack young shoots, deforming and weakening them. A spray of soapy water or an infusion of black soap and garlic can help get rid of them.
• Thrips: These small black or translucent insects pierce the fronds, causing discoloured spots to appear. A treatment based on black soap or neem oil can be effective.
• Spider mites:  They appear mainly when the air is too dry, causing the fronds to yellow and small webs to form under the leaves. Increasing ambient humidity by misting the plant regularly can limit their spread.

Frequent Diseases

• Root rot: This occurs due to overwatering or poor drainage. The roots turn black, and the fronds yellow and droop. You should then repot the plant in a more draining substrate and space out watering.
• Fungal spots: Excess moisture or poor ventilation can encourage the appearance of brown or black spots on the fronds. A spray of horsetail decoction or diluted baking soda can limit the spread.
• Yellowing or drying foliage: This is not a disease but often a sign of stress due to lack of humidity, insufficient watering, or cold drafts. The Boston fern is very sensitive to dry air. Checking the growing conditions and adjusting care usually helps the plant recover.

Prevention and Good Practices

• Avoid overwatering and ensure the pot has good drainage.
• Regularly inspect the foliage to detect early signs of pest infestation.
• Occasionally clean the fronds with a damp cloth to remove dust and limit pest proliferation.

Propagation of the Nephrolepis

Separating stolons is the simplest and most effective method to propagate Nephrolepis, unlike sowing spores, which requires specific conditions and a lot of patience.

1. Propagation by Stolons

Nephrolepis produces stolons, long creeping stems that give rise to new young plants. This method is ideal for propagating the plant without disturbing the main root ball. It allows you to obtain already developed young plants, ready to be grown in pots.

Steps:

1. Identify a stolon with a small rosette of leaves at its tip.
2. Using clean pruning shears, cut the stolon, leaving a small margin on either side of the seedling.
3. Immediately transplant it into a pot filled with a light and well-draining substrate. Place the roots on the surface and cover lightly without compacting too much.
4. Water lightly to moisten the substrate, without soaking it.
5. Place the pot in a bright location, but out of direct sunlight, with a humid atmosphere.
6. Keep the soil slightly moist and mist the fronds if the air is dry. After a few weeks (approximately 3 to 4 weeks), the new plant will begin to produce new fronds, a sign of successful establishment.

2. Propagation by Fern Spores

Sowing fern spores remains a longer and more unpredictable process. Alexandra details the technique for successfully sowing spores. 

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