Origin
Dryopteris spinulosa (O.F. Muell.) Watt var. intermedia (Muhl. ex Willd.) Underwood, commonly known as the intermediate wood fern, is a species of fern that is native to North America, Europe, and Asia. It is commonly found in rocky crevices, shady wooded slopes, and along streams and rivers.
Common Names
The plant is commonly known as the intermediate wood fern, spinulose wood fern, or narrow buckler fern.
Uses
The intermediate wood fern is primarily used for ornamental purposes in landscaping. It is commonly grown in shaded rock gardens, woodland gardens, and native plant gardens. The fern is also used in herbal remedies for various ailments such as bronchitis, rheumatism, and wounds.
General Appearance
The intermediate wood fern grows in a clump, and can reach a height of up to 24 inches, with a spread of up to 36 inches. The fronds are dark green in color and triangular in shape, with pointed tips. The fern has a delicate and graceful appearance, with thin, wiry stems that hold the fronds. The fronds are bipinnate, meaning that the branches are divided into smaller branches. The intermediate wood fern produces spores on the undersides of the fronds in the summer and fall.
Light Requirements
Dryopteris spinulosa var. intermedia prefers partial to full shade. Direct sunlight can scorch the leaves, resulting in stunted growth and reduced vigor. Therefore, it is best to grow this plant under the filtered light of taller trees or within the shelter of structures or other plants.
Temperature Requirements
The ideal temperature range for the growth and development of Dryopteris spinulosa var. intermedia is between 10°C to 21°C (50°F to 70°F). However, it can tolerate temperature fluctuations and survive mild frost. During winters, this plant goes dormant and resumes growth in the spring when temperature conditions become favorable.
Soil Requirements
Dryopteris spinulosa var. intermedia requires humus-rich, well-draining soil. It prefers soil that is slightly acidic with a pH ranging between 5.0 to 6.5. The soil needs to be kept moist, but not waterlogged, as waterlogging can lead to root rot and other diseases. You can amend the soil with organic matter such as compost or well-rotted manure to ensure proper soil conditions.
Cultivation Methods
Dryopteris spinulosa var. intermedia prefers to grow in moist, well-drained soil with partial to full shade. It can also tolerate dry soil conditions, but its growth may become stunted. The plant can be propagated through spores, division, or tissue culture. When planting, the spores or divisions should be placed at a depth of about one inch and spaced around 12 inches apart. It's important to ensure that the roots are covered completely by soil and to keep the soil moist but not overly wet.
Watering Needs
This fern requires regular watering during the growing season to maintain soil moisture. However, overwatering can lead to root rot and other diseases. The frequency of watering should be determined by the type of soil and weather conditions. It's essential to allow the soil to dry partially between watering to avoid waterlogging. Watering should also be adjusted during winter, reducing it to avoid freezing temperatures.
Fertilization
Dryopteris spinulosa var. intermedia does not require frequent fertilization but can benefit from occasional applications during the growing season. A slow-release or balanced fertilizer can be applied after new growth appears, and then again a few weeks later. It should be applied at the base of the fern at a rate of about a teaspoon per plant. Over-fertilization can damage the roots and cause leaf burn, so it's important to follow the recommended dosage carefully.
Pruning
Pruning is not necessary for Dryopteris spinulosa var. intermedia, as it doesn't produce flowers or fruit that require removing. However, it may be necessary to remove dead fronds to prevent the buildup of pests and diseases. Dead fronds can be removed manually or cut back to the base using garden shears. New growth should emerge in late spring or early summer, and the process should be repeated as necessary.
Propagation of Dryopteris spinulosa var. intermedia
Dryopteris spinulosa var. intermedia, commonly known as the intermediate wood fern, can be propagated through various methods.
Spores
One of the most common methods of propagating Dryopteris spinulosa var. intermedia is through spores. Spores are reproductive cells produced by the fern that can be collected for propagation. Spores are best collected when the fronds are mature and the sporangia (spore-producing structures) have turned brown. Collect the sporangia and place them in a paper bag. Allow the sporangia to dry, and then shake the bag to release the spores. Sow the spores on a clean, moist growing medium, and keep them in a warm and humid environment until they germinate and develop into young ferns.
Division
Another method of propagating Dryopteris spinulosa var. intermedia is through division. The plant can be divided when it outgrows its pot or when the clumps become too congested. Gently lift the entire clump of ferns from the soil, and use a clean and sharp knife or scissors to divide the clumps. Each division should have a few fronds and a portion of the rhizome. Replant the divisions in clean, moist soil, and keep them in a warm and humid environment until they establish roots.
Cuttings
Cuttings can also be used to propagate Dryopteris spinulosa var. intermedia. Take a cutting from a healthy and mature frond, making sure that the cutting is at least six inches long. Dip the cut end of the cutting in rooting hormone, and plant it in a moist growing medium. Keep the cutting in a warm, bright, and humid environment until it roots and develops into a young fern.
Propagation of Dryopteris spinulosa var. intermedia allows gardeners and plant enthusiasts to increase their collection of this unique fern. Whether it is through spores, division, or cuttings, propagating Dryopteris spinulosa var. intermedia is a fun and rewarding process.
Disease Management
Dryopteris spinulosa var. intermedia is susceptible to a variety of diseases, including fungal infections, bacterial infections, and viral infections. One common fungal infection is rust, which appears as yellowish-orange spots on the leaves. To manage rust, remove infected leaves and apply a fungicide. Another common fungal infection is powdery mildew, which appears as a white powdery coating on the leaves. To manage powdery mildew, remove infected leaves, and prune the plant to improve air circulation.
Bacterial infections are less common in Dryopteris spinulosa var. intermedia, but they can cause serious damage to the plant. Symptoms of bacterial infections include wilting, root rot, and yellowing of the leaves. To manage bacterial infections, remove infected plants and disinfect soil and pots. Prevent infections by watering at the base of the plant and avoiding overcrowding.
Viral infections are also rare in Dryopteris spinulosa var. intermedia, but they can be fatal. Symptoms of viral infections include stunted growth, mosaic patterns on leaves, and yellowing of the leaves. Unfortunately, there is no cure for viral infections, so the infected plants must be removed and destroyed.
Pest Management
Dryopteris spinulosa var. intermedia is also susceptible to a variety of pests, including aphids, spider mites, and mealybugs. Aphids are small insects that feed on the sap of the plant, causing wilting and yellowing of the leaves. To manage aphids, spray the plant with a solution of water and dish soap or neem oil.
Spider mites are tiny pests that feed on the undersides of the leaves, causing yellowing and webbing. To manage spider mites, spray the plant with a strong stream of water and apply insecticidal soap or neem oil.
Mealybugs are small, white, waxy insects that suck sap from the plant, causing stunted growth and yellowing of the leaves. To manage mealybugs, remove them with a cotton swab dipped in alcohol or insecticidal soap. For severe infestations, use a systemic insecticide.
Prevent pest infestations by keeping the plant healthy and well-watered, pruning away damaged or dead leaves, and keeping the area clean and free of debris.
