Ferns are ancient, non-flowering plants that bring a unique, lacy texture and a deep green hue to any outdoor space. Their delicate appearance belies a robust nature. These plants are most often associated with the cool, moist, and shaded conditions of a forest floor. Successfully cultivating ferns outdoors requires creating a habitat that closely mimics their native woodland setting. This guide provides practical steps for preparing the right environment and managing the ongoing care needed for these plants.
Selecting the Ideal Location
Choosing the right spot is the most important factor for the long-term health of an outdoor fern. Most ferns thrive in partial to full shade, preferring dappled sunlight or morning sun shielded from intense afternoon heat. Direct midday sun can easily scorch the delicate fronds, leading to brown, crispy edges.
Select a fern species suitable for your local climate by checking its USDA hardiness zone. Hardy ferns are adapted to survive cold winters and are the best choice for in-ground planting. Also, look for a location that offers protection from strong winds, as constant airflow can rapidly dry out the foliage and damage the fronds.
A sheltered location, such as under the canopy of mature trees or along the north side of a building, is often ideal. This placement naturally provides filtered light and reduces the drying effect of wind and sun.
Preparing the Soil and Planting
Ferns require a growing medium rich in organic matter to retain moisture while allowing for excellent drainage. Waterlogged soil is fatal, starving the roots of oxygen and causing rot. A deep, friable soil texture is preferred, allowing shallow root systems to spread easily.
The ideal soil pH for most fern varieties ranges from slightly acidic to neutral (6.0 to 7.0). If the soil is heavy clay, amend it significantly by incorporating organic material before planting. Excellent organic amendments include compost, aged manure, or well-rotted leaf mold, which mimics the natural forest floor.
When planting, dig the hole twice as wide as the root ball but only to the same depth as the nursery container. It is crucial that the crown—the central growing point—is not buried below the soil level, as this causes rot and prevents new growth.
For crown-forming ferns, the growing tips should just barely show through the soil surface after backfilling. If planting a bare-root fern, spread the roots gently in the hole before replacing the soil. Spacing varies by species, but larger ferns need enough distance to accommodate their mature spread and prevent overcrowding.
Essential Ongoing Hydration and Feeding
Consistent moisture is one of the most important requirements for outdoor ferns, as they do not tolerate drying out completely. Newly planted ferns need regular watering for at least their first year to establish robust root systems. After establishment, most ferns require supplemental watering, especially during dry spells when natural rainfall is insufficient.
Water deeply, ensuring the moisture penetrates the entire root zone rather than just wetting the surface. Focus watering on the base of the plant to keep the crown dry, minimizing the risk of fungal issues. Misting the fronds temporarily boosts humidity, which is beneficial in dry climates or during hot summer periods.
Ferns are naturally light feeders, requiring very little supplemental fertilizer. Over-fertilizing is a common mistake that can lead to frond burn, causing the tips or outer edges to turn brown. If the soil was properly amended with organic matter, additional feeding is often unnecessary.
If ferns appear pale or lack vigor, apply a light, slow-release balanced fertilizer (such as 10-10-10 or 15-15-15) once in the early spring as new growth begins. Alternatively, a top-dressing of aged compost or leaf mold each spring provides a slow, steady release of organic nutrients. Avoid fertilizing in the fall, as this encourages tender new growth just before dormancy.
Protecting Ferns from Seasonal Extremes and Pests
Managing seasonal changes ensures the longevity of hardy outdoor ferns. In preparation for winter, place a thick layer of organic mulch, such as pine needles or shredded leaves, around the fern’s crown after the first hard frost. This insulation protects the shallow root system and crown from extreme temperature fluctuations.
For deciduous ferns, leave the spent fronds in place over winter, as they provide natural protection for the crown. Cut these fronds back only in late winter or early spring before new fiddleheads emerge. Tropical ferns must be moved indoors before nighttime temperatures consistently drop below 50°F to prevent freezing damage.
During intense summer heat or drought, temporary extra watering is needed to prevent fronds from wilting or curling. Consistent shade mitigates heat stress. Ferns generally have few insect problems, but slugs and snails are common pests that feed on young fronds.
Simple, non-chemical treatments for slugs and snails include placing shallow dishes of beer near the plants or sprinkling diatomaceous earth around the base. Other occasional pests, like scale insects, mealybugs, and aphids, can be managed by gently washing the fronds with a stream of water or a mild insecticidal soap solution. Healthy ferns are naturally more resistant to most pest issues.