The Boston Fern is a lush, tropical perennial valued for its gracefully arching, feathery fronds. You can plant this fern directly into the ground, but only if your local climate allows for its year-round survival. For most gardeners outside of warm, subtropical regions, the plant must be treated as a seasonal annual or brought indoors before cold weather arrives. Planting in the ground depends entirely on protecting the fern from freezing temperatures.
Determining If Your Climate Allows In-Ground Planting
The ability of a Boston Fern to survive outdoors year-round is dictated by its temperature tolerance. This fern is reliably perennial only in United States Department of Agriculture (USDA) Hardiness Zones 9 through 11. These zones ensure the fern’s root crown will not experience damaging freezing temperatures during the winter months.
If you live outside of these warmer zones, the fern will not survive winter planted directly in the soil. Even a light frost can cause irreversible damage to the fronds, and a hard freeze will destroy the entire root system. The ideal minimum temperature for the Boston Fern is above 55°F. Before planting, check your specific zone to determine if your climate can support this plant permanently.
Ideal Soil and Light Conditions
Once your climate is suitable for in-ground planting, selecting the proper location is crucial. Boston Ferns thrive in a site that receives bright, indirect light or dappled shade throughout the day. Direct afternoon sun, especially in hot summer climates, will scorch the foliage and cause the fronds to turn brown. The best placement is typically under the canopy of larger trees or on the shaded north side of a structure.
The soil must be rich in organic matter, loose, and well-draining, yet capable of retaining consistent moisture. These plants prefer a slightly acidic to neutral soil pH, ideally ranging between 5.5 and 6.5. If your garden soil is heavy clay, amend the planting area by incorporating compost, leaf mold, or aged manure to improve aeration and drainage. Poorly draining soil quickly leads to root rot, which is a common killer of in-ground ferns.
Seasonal Care and Maintenance
Consistent moisture is essential for Boston Ferns planted in the ground during the growing season. The soil should be kept uniformly moist but never waterlogged, which can be a challenge in summer heat. In-ground plants may require more frequent watering than container-grown specimens, particularly during dry spells.
Boston Ferns are not heavy feeders, but they benefit from regular nutrient replenishment. You can apply a balanced, water-soluble fertilizer, often at half strength, every four to six weeks to support lush foliage growth. Alternatively, amending the soil surface with a fresh layer of compost or organic mulch annually provides slow, steady nutrient release. Routine maintenance includes removing old, brown, or yellowing fronds by cutting them off near the soil line to encourage growth from the central crown.
Preparing Ferns for Winter
For gardeners in marginal USDA Zones, such as 9a, where light frosts are possible, a protective layer is necessary. In late autumn, trim back any damaged fronds and apply a thick, insulating layer of organic mulch, such as pine straw or shredded leaves, over the fern’s crown. This material helps stabilize the soil temperature and protect the dormant root structure from freezing.
If you are in a colder climate, the entire fern must be lifted from the ground and overwintered indoors. Before the first expected frost, carefully dig up the fern, place it into a pot, and cut the foliage back to about four inches above the soil line. The potted fern should be moved to a cool location, such as a garage or basement, where temperatures remain above 55°F. During this dormant indoor period, reduce watering to roughly once a month, allowing the soil to dry slightly between applications, and withhold all fertilizer until spring.