How to Grow and Care for Japanese Bird's Nest Fern (Asplenium Antiquum)

Why not consider a Japanese bird's nest fern (Asplenium antiquum) if you're looking for a unique houseplant to add to your collection? Similar to, and often confused with, the bird's nest fern (Asplenium nidus), this striking plant has fronds that don't actually look like fronds. Instead, mature fronds are flat, long, and shiny with a decorative wavy edge. The tongue-like greenery grows in an upright rosette form that some say resembles a bird's nest. Mature plants also develop a strong, distinctive brown midrib in the center of the nest.

As with most fern types, the Japanese bird's nest fern has quite particular care requirements. Japanese bird's nest ferns make great bathroom plants—they need high humidity levels, even moisture, and medium to lower light conditions to thrive. They can also be grown outdoors in warm, humid states that mimic their native tropical habitats.

Asplenium Antiquum Care

Here are the main care requirements for the slow-growing Japanese bird's nest fern:

• Position your plant in a north or east-facing window with moderate, indirect light.
• Plant in a rich, loose, well-draining potting mix. A peat-based fern mix is ideal.
• Water from the base once the top couple of inches of soil is dry and avoid soggy conditions.
• Offer warm temperatures and high humidity.
• Feed with a weak fertilizer monthly during the growing season.
  

Light

Outdoors, these plants are very sensitive to leaf scorch in moderate light and often do better in deeper shade. When grown as a houseplant, mature plants can handle more light, but avoid direct sun or full shade positions. Locate in or near a north or east-facing window which offers medium, indirect light. In areas with lower light, humidity must be higher to promote healthy growth.

Soil

Grow your Asplenium antiquum outdoors in well-draining, organically rich, slightly acidic soil. Indoors you can purchase a fern potting medium or make up your own peat-based mix. A mix of one part peat moss (or coco coir for a sustainable alternative), one part perlite or vermiculite, and one tablespoon of activated charcoal per liter of mix could provide the drainage required.

Water

While many ferns are particular about having even moisture, epiphytic Asplenium antiquum often grow on tree branches in their native habitat. This means they are more sensitive to overwatering, and soggy soil leads to root rot.

Wait until the top couple of inches of the potting medium are dry, but no more, before watering thoroughly. These plants don't appreciate top watering, and water lurking in the base of the rosette leads to crown rot. Carefully water from the base around the edges of the rosette. Depending on your indoor heat and humidity, you might water around once a week and less in the winter.

Temperature and Humidity

This tropical plant needs higher-than-average humidity levels and warm temperatures to thrive. Ideal humidity levels are around 70%, making this the trickiest part of their care. Asplenium antiquum will struggle when humidity levels drop below 50%. If your home is dry, invest in a humidifier, group humidity-loving plants together, and place the container on a water-filled tray of pebbles.

When grown outside, Asplenium antiquum tolerates temperatures down to 50 degrees Fahrenheit. However, temperatures between 60 and 80 degrees Fahrenheit promote the healthiest and fastest growth, especially indoors.

These plants aren't fans of drafts, so keep them away from air conditioning or poorly-sealed windows.

Fertilizer

Asplenium antiquum aren't heavy feeders, but offering a monthly application of a weak dose of balanced liquid fertilizer to the soil during their growing season can help speed up their notoriously slow development. Don't let the fertilizer touch the fronds, as it can burn them, and avoid high-nitrogen formulas and overfeeding, as this can result in deformed, discolored, and unhealthy fronds.

Pruning

Japanese bird's nest ferns don't need any major pruning. In fact, new fronds are very tender and require careful handling. However, cutting off any dead or dying outer leaves helps direct energy to healthy new growth.

Propagating Asplenium Antiquum

Propagating Japanese bird's nest ferns is a challenging undertaking. These plants are slow-growers with delicate fronds, so division is tough and can send the mother plant into shock. Growing from spores (the fern equivalent to seeds) is even more challenging and not often successful in a home environment. However, if you have patience and want to give propagating Asplenium antiquum from spores a whirl, here's how:

1. Wait for the spores to ripen. You'll know they are ready to harvest when they darken, become fuzzy and start to fall off the frond's undersides.
2. Cut off a healthy, mature outer frond, being careful not to disturb the sensitive fronds around it.
3. Leave the cutting on top of some kitchen towel or in a paper bag in a dry spot that isn't drafty.
4. Wait for the spores to drop off the fronds by themselves. Trying to pull them off can cause damage.
5. Gently shake the spores onto the top of a sterile fern potting mix or damp sphagnum moss, and push them down to ensure good contact.
6. Use a water spray on a fine mist setting to moisten the spores and potting medium.
7. Hold in the moisture and humidity by covering the container with plastic.
8. Put the container in a tray with two inches of water in the base.
9. Choose a warm position where the soil is exposed to bright but indirect light.
10. Don't let the water in the tray dry out. Top up regularly and check to make sure the soil surface remains evenly moist but not soggy.
11. Wait for prothalli—little heart-shaped shoots—to appear. When they do, gently transplant them into individual pots.
12. Leave the containers uncovered in the same bright spot and keep the potting mix evenly moist but not waterlogged.
13. It can take six to 12 months for proper fronds to appear.
    

Potting and Repotting

These slow-growing plants won't need repotting regularly, and because their fronds are delicate, only do it when necessary and very carefully. You'll know when it is time because the heavy midrib will be causing the plant to be unstable in its current pot.

Select a new pot around 2 inches in diameter larger than the old one, and with good drainage holes. Replace the old potting medium with a fresh, rich, loose mix.

Common Pests & Plant Diseases

Asplenium antiquum aren't bothered by too many pests and diseases. However, fungal problems can occur due to poor air circulation or improper top watering.

Occasionally you might have to control aphid infestations or other common houseplant pests such as mealybugs, scale, or fungus gnats. But, if you don't let things get out of hand, they are usually easily treated with natural insecticidal soaps. As always with Japanese bird's nest ferns, take care not to damage the delicate fronds while treating.

Common Problems With Asplenium Antiquum

If you don't get things right with the Asplenium antiquum care, these plants often offer early warning signs that something must change. Watch out for the following:

Frond Deformities

If your Japanese bird's nest fern is in an overly sunny, dry spot or overfertilized, the fronds can lose their distinctive wavy, upright form, and growth will slow down significantly. Move your plant to a lower light position, up the humidity, and ease up on feeding to try to resurrect those wavy edges.

Pale or Yellowing Fronds

Too much sun, overfertilizing, or overwatering can result in the fronds of your Asplenium antiquum turning from glossy green to a pale green or yellow shade. Move your plant or introduce a sheer curtain over the bright window, and ensure you only water once the top two inches of the potting medium are dry.

Brown Fronds

Old fronds turning brown and dropping is to be expected on mature plants. However, Asplenium antiquum is also prone to leaf scorch, which can brown tips when it receives too much light. Dry air also contributes to brown, curling tips. Insufficient humidity and drafty conditions are major killers of Japanese bird's nest ferns, so always focus on maintaining the moisture.