The narrow sword fern (Nephrolepis cordifolia ‘Duffii’), also known as the Lemon Button Fern, is a popular choice for indoor and outdoor spaces. It offers a compact growth habit, distinctive foliage, and a subtle lemony scent when brushed. This fern is a favored option for those seeking a vibrant addition to their plant collection.
Identifying Narrow Sword Fern
The narrow sword fern features narrow, sword-shaped fronds that grow in a compact, bushy manner. A distinguishing feature is its small, rounded, “button-shaped” leaflets, arranged in a double row along each frond. These fronds are bright green, sometimes with a golden hue.
This dwarf variety generally reaches a height and spread of about 12 to 18 inches (30 to 45 cm). Its smaller stature makes it suitable for various settings, including small spaces or terrariums.
Ideal Growing Conditions
Narrow sword ferns prefer bright, indirect light, mimicking their natural understory habitat in tropical regions. Direct sunlight can scorch fronds, so place them near a window with filtered light or in a partially shaded area. They can tolerate lower light conditions, though growth might be less vigorous.
Well-draining, moisture-retentive soil is preferred. A potting mix rich in organic matter, such as peat moss, perlite, and pine bark, works well. This ensures adequate drainage while retaining consistent moisture. The soil should remain consistently moist but never waterlogged, as soggy conditions can lead to root issues. Water when the top inch or two of soil feels dry.
High humidity (60-90%) is beneficial; low humidity can cause frond tips to brown. Misting, using a pebble tray, or placing the plant in a humid room like a bathroom can help provide moisture. Temperatures should range from 60-75°F (16-24°C), and the plant needs protection from cold drafts and sudden temperature fluctuations.
Care and Maintenance
Fertilization is beneficial during the active growing season, typically spring and summer. Apply a balanced liquid houseplant fertilizer, diluted to half or quarter strength, every two to four weeks. Over-fertilizing can lead to salt buildup and damage to the fern’s roots.
Prune by removing any dead, yellowing, or damaged fronds to encourage new growth and maintain the plant’s shape. This helps the plant direct energy towards healthy development. For severe browning or decline, cutting fronds back to about 2 inches from the soil line can rejuvenate the plant.
Repot every two to three years, or when the fern outgrows its container. Spring is the preferred time. Choose a pot one size larger with good drainage holes. When repotting, keep the rhizomes at the same soil level to prevent rot.
Common Challenges
Browning frond tips or edges often indicate insufficient humidity, a common problem in dry indoor environments. Increasing ambient humidity through misting, pebble trays, or humidifiers can help.
Yellowing leaves often signal inconsistent watering, particularly overwatering, which can lead to root rot. Ensure well-draining soil and allow the top layer to dry slightly between waterings to prevent sogginess. Underwatering can also cause leaves to turn brown and crispy. Temperature stress from drafts or sudden changes can contribute to reduced growth and leaf drop.
Pest infestations, such as spider mites, aphids, or scale insects, can occur, especially in dry conditions. Regularly inspect the plant, particularly the undersides of leaves, for early detection. Treat promptly with insecticidal soap or neem oil.