When grown indoors, bird’s nest ferns (Asplenium nidus) grow relatively slowly, in my experience, gaining only a few inches per year under average growing conditions in my home. Fronds typically max out at around 2 to 3 feet long. The fronds radiate out from a central rosette, and plant diameter may reach up to 3 feet over time. When grown outdoors, fronds may reach 5 feet long and 8 feet wide. In this guide, I’ll cover how big and fast a bird’s nest fern grows to help you plan your collection accordingly.
Bird’s Nest Fern Growth Indoors vs. Outdoors
When grown indoors under optimal conditions, bird’s nest ferns grow slowly, from two to six inches per year. Fronds eventually reach a maximum size of about 3 feet long, with plant diameter maxing out at about 3 feet wide.
When grown outdoors, bird’s nest ferns grow faster. Fronds may reach lengths up to 5 feet long, with a maximum diameter of around 4 feet.
The ferns grow faster in their natural habitat as they’re able to access the right soil, water, light, and nutrient conditions. Growing in a container indoors also constrains growth rate and size.
Bird’s Nest Fern Natural Growth Cycle
Bird’s nest ferns have active growth during the spring and summer and produce new growth during these months.
Growth slows in the fall and remains very slow during the winter months.
On average, bird’s nest ferns may reach their full size within a few years. However, plant growth rate depends on environmental conditions such as temperature, humidity, light levels, soil, and more.
Factors Contributing to Growth Rates
Care and Maintenance of Bird’s Nest Ferns
While bird’s nest ferns aren’t considered high-maintenance houseplants, they still need proper care for optimal growth rates. This includes:
- Indirect light exposure
- Consistently moist (but never wet) soil
- Soil with an acidic pH
- 20-10-20 fertilizer, diluted to half strength, applied monthly during the growing season
- Adequate humidity
- Occasional pruning to encourage healthy, new growth.
When grown indoors, place bird’s nest ferns in a spot that receives medium indirect light or low light. Consider a spot in a north-facing window, near an east-facing window, or a window covered by a sheer curtain.
Common Reasons Growth is Slow or Stunted
As with many houseplants, bird’s nest ferns suffer when overwatered. These tropical plants prefer soil that’s consistently moist but never wet. Sitting in wet soil can slow growth or even lead to root rot and plant death.
Water your bird’s nest fern only when the top inch of soil feels dry. Add water around the plant’s perimeter, never directly into the rosette.
Lack of Light
If your bird’s nest fern doesn’t get enough light, it can’t perform photosynthesis. This is the process by which plants transform sunlight into the energy and nutrients they need to survive.
Place your bird’s nest fern in a spot that receives medium indirect light or filtered light for optimal growth rates. Try to mimic the dappled light conditions found in the fern’s native habitat.
Pests and Diseases
Certain bird’s nest fern pests and diseases can slow or stunt your fern’s growth. Common issues include:
- Scale: These small insects often cause brown spotting on foliage, which can be mistaken for spores
- Foliar nematodes: Look for small, translucent spots on foliage that turn brown or black
- Fungus gnats: Larvae may munch on roots and stems
- Spider mites: Strip out chlorophyll from fronds and make webs
Poor Soil Base
Bird’s nest ferns need a suitable soil base to get the nutrients, water, and air they need to survive. Choose a moist, well-draining soil with an acidic pH around 5 to 6.5.
Overfertilizing creates more problems than under-fertilizing. Bird’s nest ferns only need feeding during their growing season.
Apply a 20-10-20 fertilizer, diluted to half strength, once a month during spring and summer only. Overfertilized plants may develop abnormally shaped fronds with areas of yellow and brown along the margins.
Bird’s nest ferns grow best in a warm, humid climate. Temperatures around 70 degrees F are ideal. If temperatures drop below 50 degrees, plant growth may creep to a halt.
How to Make Your Bird’s Nest Fern Grow Faster
The Best Soil Types
The soil you choose affects your bird’s nest fern’s growth rate. For optimal growth, choose an acidic (pH 5 to 6.5) soil mix that’s well-draining while retaining moisture.
Choose a soil mix containing coco coir, peat, perlite, and pine bark. This mix works well if you’re considering propagating your bird’s nest fern as well.
The Best Light Conditions
Ideal light conditions for a bird’s nest fern are medium indirect light, filtered light, or reflected light. In a north-facing window, near an east-facing window, in a window with a sheer curtain, or in an area with reflected light are all good choices.
Ideal Temperature & Humidity
As tropical plants, bird’s nest ferns prefer warm, humid temperatures. Aim for a spot with consistent temperatures around 70 degrees F for optimal growth. You may increase humidity by setting your plant’s container on a small tray filled with rocks and water.
When and How to Fertilize
Apply fertilizer only during the spring and summer months. Use a water-soluble 20-10-20 fertilizer that’s been diluted to half strength and apply once a month to the soil.
When and How to Repot
If your fern is root-bound, growth will slow or stop. Repot bird’s nest ferns every couple of years into a larger container. Using rich, well-draining will ensure the container has adequate drainage holes.
Bird’s nest ferns add tropical drama to any room with their shiny, crinkled fronds and attractive rosette form. When grown indoors, they grow slowly, reaching widths of 3 feet with 2 to 3-foot-long fronds. Providing your fern with the right growing conditions may increase its growth rate.
Linsay is an American copywriter based in the Pacific Northwest with a background in academic writing and research. Linsay holds Master's degree in both Anthropology and Library and Information Sciences and has written for numerous national and international publications including USA Today, SFGATE, Hunker, and The Bump across an array of topics in the gardening, green living, and travel sectors. When she's not writing, you'll usually find Linsay reading, kayaking, sailing, snowboarding, or working in her garden.