Ferns for every level

A selection of indoor ferns for every level of gardening expertise. With about 10, 560 known species, beginners and experts alike have plenty to choose from. 

About ferns

Vincent Pau https://commons.wikimedia.org/wiki/File:Fern_House_Ooty_Botanical_Garden_(125298853).jpeg

Ferns come in a huge array of shapes and sizes. They are very primitive plants. The earliest fern fossils date from about 360 million years ago, before the time of the dinosaurs. They were among the earliest land-based life forms and are so old that they do not flower or produce seeds: these reproductive innovations came much later. Ferns reproduce instead by dispersing spores. 

In evolutionary terms, the fern group has been very successful. Judging from the fossil record, many species have remained relatively unchanged for millions of years. A prime example is the Osmunda claytoniana  (the interrupted fern), a popular garden plant with fossil records dating back 200 million years. 

Different ferns have a diverse range of care needs. But most appreciate humidity and low light levels. These conditions mimic their primordial natural habitat - the damp, cool crevices of forest undergrowth. 

Humidity: a must for ferns

The most common pitfall of fern care is a lack of humidity. Most indoor spaces will not have enough moisture in the air to keep ferns happy.  

However, different fern species tolerate different humidity levels. Some easier plants will be forgiving about some dryness in the air.

The fussier species need to to live inside a closed or open glass terrarium. A terrarium is the best way to trap lots of air moisture around your plant while still letting in light. But there are several other strategies for maintaining high local air humidity:

1. Place a group of ferns on a tray of pebbles with water half-way up the depth of the pebbles. Make sure the bottom of the pot doesn't touch the water as this will make the soil too soggy. The idea behind the pebble tray is that the pebbles give a larger surface area for water to evaporate off of. Grouping plants together also increases humidity in their immediate surroundings. 

2. Mist with a bottle spray several times a day. If you have a busy schedule and are likely to forget, opt for the pebble tray. 

3. Get a humidifier. This is one of the most effective ways of raising air humidity, especially if you have a large number of humid-loving plants indoors.

Easy ferns

Bird's Nest Fern (Asplenium nidus)

Forest and Kim Starr https://commons.wikimedia.org/wiki/File:Starr-061108-9605-Asplenium_nidus-in_pot-Hoolawa_Farms-Maui_(24500802809).jpg

This is among the easiest indoor ferns to grow. They are rainforest plants, making them ideal indoor companions with their preference for warmth. Temperatures lower than 50 degrees Fahrenheit may kill the plant. 

Their relatively thick, belt-like leaves retain moisture more readily than some of the delicately lacy ferns. This mean that the Asplenium antiquuum are much more forgiving when it comes to lower air humidity than other species. Although they still appreciate high humidity, they will not wilt at the first hint of dryness in the air. 

There are several varieties of Bird's Nest ferns distinguished by leaf shape. The Asplenium nidus 'Crispy wave' has very pronounced ruffles while Asplenium nidus 'Antiquum' has slightly rippled leaves.

When it comes to light needs, they are similar to most other ferns - filtered light with moderate shade is best. The easiest way to kill a fern is by exposing it to direct sunlight. 

Water when the top inch of soil is dry. Add half-strength fertilizer from April to September (add half the amount of fertilizer than the packaging instructions recommend) once a month. 

Japanese Holly Fern

David J. Stang https://commons.wikimedia.org/wiki/File:Cyrtomium_fortunei_5zz.jpg

Like the Asplenium nidus (above), the leaves of the Japanese Holly Fern are tougher and more moisture-retaining than the delicate varieties which need high humidity. Its spiky looks will add a dramatic touch to your space. It can tolerate low to moderate air humidity, making it an ideal fern for indoors.

The soil will need to be slightly moist at all times. Moistened pebbles can be kept on the surface of the potting mix to trap some water inside the soil. At the same time, waterlogged soil is a no-no for any fern. Never let the fern stand in water. When you water, hold the pot under a tap for about 30 seconds and let all the excess water drain fully through the pot holes.

The soil should be well-drained with lots of organic matter like loam and leaf mold. Place in partial or full shade. 

Medium difficulty ferns

Fishtail fern (Microsorum punctatum)

Krzysztof Ziarnek, Kenraiz https://commons.wikimedia.org/wiki/File:Microsorum_punctatum_%27Serratum%27_kz02.jpg

The fronds of the fishtail fern come in a mesmerizing shape. It brings to mind not just fish tails but also mermaids fins or seaweed fronds. Like most ferns, it grows in partial shade or dim light. It prefers acidic soil of between 4.0 and 7.0 pH.

What makes the fishtail fern more difficult to care for is that it will not tolerate low humidity. It is best grown in a bathroom or in a terrarium. On the other hand, it is quite tolerant of drought for a fern so forgetting to water very occasionally will not kill it.

The fishtail tern needs soil that it rich in organic matter but still quite loose and well-draining. A suitable potting medium would be three parts coarse (not ground) peat moss, three parts leaf cold, two parts perlite. 

These ferns are epiphytes. This means that in the wild they can grow by clinging to other plants, especially trees. If you want to get creative, you can mount this fern on wood. Wrap the rhizomes completely in sphagnum moss and secure the moss ball to a piece of bark or cork using garden string. Hanging the bark makes an interesting display. To water your mounted plant, you should place it in a full sink for about a minute and then leave it out on a dry surface so that excess moisture drips out. 

The Australian tree fern (Sphaeropteris cooperi)

C T Johansson https://commons.wikimedia.org/wiki/File:Sphaeropteris_cooperi-IMG_6511.JPG

This fern would look at home in a primeval forest. Their trunks are thick and scaly, topped by large leafy fronds. Like other ferns, it appreciates partial shade. 

The Australian Tree Fern can be grown either outdoors or indoors but it requires high humidity so will be happiest in a greenhouse. Its size will also be a challenge for indoor growing -  it can grow up to 25 feet or more. Under the right conditions, this tree is a fast grower. In Hawaii, it has escaped cultivation to become an invasive plant. 

It needs soil with lots of leaf-mold that must be kept moist at all times. This can be made by composting grass clippings from lawn movers or can be bought. 

Expert difficulty ferns

Hart's-tongue Fern (Asplenium scolopendrium)

Daderot https://commons.wikimedia.org/wiki/File:Asplenium_scolopendrium_-_Botanischer_Garten_der_Universität_Würzburg.JPG

This fern is difficult to grow indoors because it requires very particular conditions. It needs well-draining but damp alkaline soils with lime and prefers cooler summer temperatures. Damp tufa is an ideal potting medium. 

There is a European and an American variety of this fern. In Europe, you can sometimes see it growing happily outdoors in cracks in the wall at precarious heights. The American variety is much rarer in the wild is fiendishly difficult to cultivate. 

Maidenhair spleenwort (Asplenium trichomanes)

 Björn S https://commons.wikimedia.org/wiki/File:Asplenium_trichomanes_(35088454291).jpg

This compact and perfectly formed fern has many delicate ovate leaves on their fronds.

Because of its high humidity needs, this plant is best grown in a closed terrarium. Place a 2 inch or so layer of charcoal at the bottom of the terrarium - this will soak up excess moisture which will prevent mold. Above the charcoal layer, place a potting mix of one part loam, one part leaf mold, and sharp horticultural sand.