The Indoor Sword Fern (Nephrolepis exaltata) is a popular houseplant known for its lush, tropical appearance. Its graceful, arching fronds make it suitable for hanging baskets or pedestals, allowing its foliage to cascade freely. The sword fern also helps purify indoor air by removing pollutants like formaldehyde and xylene, contributing to a healthier environment.
Essential Conditions for Thriving
Successful care requires replicating the warm, humid conditions of its native tropical habitat. High humidity, ideally above 50%, is necessary for a healthy fern. To increase humidity, group the fern with other plants or place the pot on a shallow tray filled with pebbles and water, ensuring the pot does not sit in the water. While regular misting offers a temporary boost, a small room humidifier provides the most consistent solution, especially during dry winter months.
The fern requires bright, indirect light for dense, vibrant growth. An east-facing window provides gentle morning sun, or the plant can be placed a few feet away from a south- or west-facing window. Direct, intense sunlight burns the foliage, causing bleached or brown patches, while insufficient light leads to sparse growth and yellowing. The ideal temperature range is 60 to 75°F (15–24°C). Keep the fern away from cold drafts or heat vents that cause rapid temperature fluctuations.
Consistent watering is necessary to keep the soil evenly moist, avoiding saturation or waterlogging that causes root rot. Water thoroughly until liquid drains from the holes. Check the top inch of soil; if it feels dry, water again. Use a well-draining, peat-based potting mix, which retains moisture while allowing excess water to escape. During the active growing season (spring and summer), feed the fern once a month using a balanced, liquid houseplant fertilizer diluted to half-strength.
Troubleshooting Common Problems
Browning of frond tips and edges is often attributed to low humidity, which causes the foliage to dry out and shrivel. Browning can also signal mineral buildup from tap water, as the fern is sensitive to salts and chlorine. Switching to distilled water or filtered rainwater for irrigation can resolve this mineral toxicity.
Severe and widespread browning may result from excess fertilizer, which causes a salt buildup that burns the roots. To correct this, flush the soil by slowly pouring a large volume of water through the pot to wash away the excess salts. Yellowing fronds usually indicate a watering imbalance, either overwatering or severe underwatering. Overwatering is common, preventing roots from accessing oxygen and leading to root decline and yellowing foliage.
Sword ferns are generally pest-resistant but can be targeted by mealybugs or scale insects. Mealybugs appear as small, white, cottony masses, usually where the fronds meet the stem. Scale insects manifest as tiny, hard, brown bumps on the stems and undersides of the fronds. For minor infestations, manually remove pests using a cotton swab dipped in rubbing alcohol. Persistent issues require a targeted application of neem oil or insecticidal soap applied thoroughly to all parts of the plant.
Expanding Your Collection
Propagation by division is the most effective technique, ideally performed when repotting in the spring. As the fern matures, it forms a dense root ball composed of separate clumps. To divide the plant, gently remove it from its container and use a clean, sharp knife to cut the root mass into smaller sections.
Division and Rejuvenation
Each division must include a portion of the root system and several healthy fronds for a successful transition. These sections should be potted individually in fresh, well-draining soil. Division serves the dual purpose of propagation and rejuvenation, preventing the original plant from becoming root-bound and encouraging renewed growth.
Runners and Spores
The fern also produces runners (stolons), which are slender stems that trail over the soil and occasionally form small plantlets at their tips. These plantlets can be separated and potted once they have developed a few roots. While propagation via spores is possible, it is a complex and time-consuming process reserved for commercial growers.