Boston fern: growing & caring for Nephrolepis exaltata

The Boston fern is not only easy to care for, but also an interesting primeval plant and an eye-catcher in the home and office.

Here you will learn what an appropriate location for the Boston fern (Nephrodlepis exaltata) looks like, and get tips and tricks on care and propagation of the tropical plant. We also present the most popular houseplant varieties.

Boston fern: origin and characteristics

The Boston fern is also known as the sword fern, wild Boston fern, Boston Blue Bell Fern, tuber ladder fern, or fishbone fern. The fern with its green fronds brings a little piece of the jungle into your home. It is a genus of plants within the swordfern family (Nephrolepida). There is still disagreement about the number of species, which is estimated at about 30. Boston ferns grow in tropical and subtropical forests either on the ground or epiphytically, that is, perched on other plants. These evergreen perennials have pinnate leaf fronds that grow rosette-like from the centre of the plant. They usually hang over the edge of the pot, which is why the fern looks especially good in a hanging basket.
The plant is also said to have an air-purifying effect, which makes the fern all the more popular as a houseplant.

Did you know? Ferns are among the oldest plants on our planet. They populated the land more than 300 million years ago. They do not form flowers, but use spores located on the underside of the leaf for reproduction.

The most beautiful varieties

The Boston ferns include several varieties specially bred for indoor cultivation. Here we give a brief overview of the most popular examples.

• Nephrolepis exaltata ‘Fluffy Ruffles’: This is a miniature cultivar with bifid leaves. This means that the individual leaflets of the fronds are divided again. This results in the “fluffy” appearance.
• Nephrolepis exaltata ‘Green Lady’: This variety impresses with a bushy, dense growth and a medium green leaf colour.
• Nephrolepis exaltata ‘Variegata’: Unlike the other varieties, the leaves of this variety of heavy fern are not completely green, but green/light green/white variegated.

Growing Boston ferns: location, soil and procedure

The ideal location is humid, warm and semi-shade to light, but not sunny, especially at midday. Since in nature the fern grows under the protection of other plants, it should never be exposed to full sun, even in the room. Nevertheless, it needs some light for healthy growth. The temperature should be around 20 °C all year round and should not drop below 18 °C. Since the Boston fern loves moist air, it should preferably not be placed near a drafty window or above a heater. Good conditions for the fern include the bathroom, if there is enough light to penetrate. If you want to keep the sword fern in the bedroom or another place in the home, you need to keep the humidity high by spraying the plant occasionally. It is also possible to keep them in hydroculture, in which case the humidity in the immediate vicinity of the fern is automatically increased somewhat.

The substrate for the Boston fern, first of all, must have a high water storage capacity. A loose structure is also advantageous. For example, a sustainable choice is our Plantura Organic All Purpose Compost. It consists of natural raw materials and does not contain peat. To prevent waterlogging, a drainage layer of broken clay or similar coarse material should be laid on the bottom of the pot.

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In the summer months, the sword fern can also be placed outside. Again, you should choose a location protected from the sun and slowly accustom it to the new position. So put it outside first for a few hours on the first few days, then gradually longer and longer. From September, the fern should be brought back into the house. To increase the humidity, you can fill the trivet with expanded clay balls and pour water on it. If you now place the pot on the balls, the Boston fern with the roots, while not in the water, still benefits from the evaporative moisture.

Boston fern care

In addition to a suitable location, the fern requires care so that it can develop to its full magnificent extent. This includes, first of all, regular watering and fertilising.

Watering, pruning and fertilising

The moisture-loving sword fern should be watered regularly – but not excessively. It likes a constantly moist root environment, but not waterlogged. Therefore, remove the excess water that collects in the saucer. Ideally, use lukewarm rainwater or other water free of lime. Stale tap water can also be used. Also, the water for spraying the fronds should not contain lime, if possible.

You do not have to prune the Boston fern, but you can remove dried up, yellow or overlong leaves. Cut them off at the base with a sharp knife. Boston sword ferns tolerates pruning and will resprout.

If you fertilise the houseplant, it will grow green and lush with an appropriate dosage. In the growing season from spring to autumn, you can give the plant a green plant fertiliser every two weeks through the watering water. For this purpose, for example, our Plantura Liquid Houseplant Food, which provides nitrogen and potassium in the appropriate ratio for lush foliage in ornamental plants. For the Boston fern, a fertiliser application at half the dosage is sufficient. After repotting, you do not need to fertilise for the first three months. Even in winter you can omit the fertiliser.

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Is the Boston fern hardy?

The sword fern is not hardy outdoors here, because it requires relatively high temperatures even in the cold season. A room temperature above 12 °C is necessary for the Boston fern to continue to do well. Nevertheless, the fern grows more slowly in the winter, meaning it needs less fertiliser at this time.

In the spring you can repot the fern. Young specimens ideally every year, older ones only every three years, or when the root ball completely fills the pot. Use a larger pot and do not fertilise for the first few months after repotting.

Fern losing leaves: what you can do

Are the leaves of your Boston fern withering or turning brown, or is it even losing its fronds? This can have a variety of causes. Once you have identified the reason, it is possible to save the plant.

• Dry air: It is often difficult to keep the humidity of the air reasonably high. The fronds can then dry up and turn brown. Place a bowl of water next to the plant and spray the fern with lime-free water every few days.
• Dry soil: Dry soil can also cause wilted fronds because water can no longer be transported from the roots to the leaves. Finger test to see if the soil is still moist enough, and water more frequently if necessary.
• Direct sun: Since ferns are naturally accustomed to shady or semi-shady places, too much light can sometimes lead to brown, discoloured leaves. Simply place the sword fern in a less bright location.
• Fertiliser: Too much or too little fertiliser can also cause leaf discolouration. Therefore, be careful not to use too much fertiliser, and fertilise a little less at first on a trial basis.

Propagating Boston ferns

There are several methods by which the fern can be propagated. In addition to the division of the mother plant and the use of offshoots, you can also try your hand at propagation via spores.

The easiest way to propagate is by dividing the root ball. If you are repotting the Boston fern, you can simply split the root ball in two and plant the two plants in separate pots. However, this method works only for older plants, which already have several rosettes of leaves.

Propagation via offshoots is also possible with older specimens. These form small runners from the root ball, which in turn can be separated and planted in their own pots. Keep the seedlings nice and moist and provide adequate humidity.

Propagation via spores is not quite as simple, but it can succeed. When the spore capsules on the underside of the leaf are brown and mature, you can cut off one of the fern fronds and place it on a piece of newspaper. The capsules should open after some time and the spores should fall onto the newspaper. Now you need to carefully distribute them on growing substrate. Our Plantura Organic Herb & Seedling Compost is ideal for this purpose, with its properties is precisely tailored to the needs of young plants. Spray the spores with water and cover everything with cling film. This can be aired every few days. The jar is best placed in a warm place. Over time, a mossy coating should form. This must be carefully placed on new substrate with the help of a spoon and put in a bright place. With luck, small sword ferns will form here in a few weeks. Always make sure to use clean tools and sterile, boiled water.

Is the sword fern poisonous?

Boston ferns are mildly toxic, meaning they contain toxic substances in such small amounts that even eating the fronds is considered safe. Accordingly, the fern is not poisonous to cats, dogs or other pets, and you do not have to worry about your children.

Another interesting fern for indoor keeping is the bird’s nest fern. Our article will explain what makes it so special and how to care for it.