Boston fern (Nephrolepis exaltata), also known as sword fern, is a popular fern species that grows in many tropical areas around the world. In North America, it is considered a classic houseplant and is easy to care for, as it doesn’t require a lot of sunlight. Outdoors, this plant thrives in swampy, humid, and forested areas, and makes a good choice for partial-shade gardens in places like Southern California or Florida. Its sword-shaped, blue-green foliage contains tiny leaflets and grows erect, arching only when fronds grow larger. Like several other fern species, Boston fern is a slow grower and is best planted outdoors in the fall or spring or indoors year-round.
|Common Names||Boston fern, sword fern, ladder fern, boss fern|
|Botanical Name||Nephrolepis exaltata|
|Plant Type||Herbaceous, perennial|
|Mature Size||2 to 3 feet tall and wide|
|Sun Exposure||Partial sun|
|Soil Type||Moist, well-drained|
|Soil pH||Acidic (6.0 to 6.5)|
|Hardiness Zone||10 to 12 (USDA)|
|Native Area||Americas, Africa, Polynesia|
Boston Fern Care
Boston fern appreciates a little TLC. It likes warm and humid conditions and doesn’t enjoy outdoor temperature extremes or indoor drafts from air conditioners or heating vents. It’s important to maintain stable growing conditions for Boston fern, as any fluctuation in care may quickly damage the plant.
Water Boston fern frequently to prevent the soil from drying out and fertilize the plant regularly during its active growing stage. Misting your fern helps to raise the ambient humidity and is a must-do practice if you live in a dry climate. Pruning your fern isn't a major chore. Simply remove dead fronds as needed to keep the plant looking attractive. Generally speaking, this plant only falls victim to pests or diseases when it's grown outside and neglected.
Watch Now: How to Grow and Care for a Boston Fern
Boston fern does best when grown in a location with bright, indirect light. Too much shade can result in sparse fronds that appear lackluster, and too much sun can burn the fronds. For this reason, Boston fern is a good choice for a porch plant that receives filtered sun in the morning and afternoon shade.
Ferns like organically rich, loamy soil with good drainage. Adding compost and peat to your outdoor garden before planting is typically recommended. For a potted Boston fern, use a peat-based potting mix with added perlite for increased drainage capacity. Poorly drained soil can cause root rot, which will ultimately kill this plant.
The key to successfully growing a Boston fern is to keep the soil lightly moist—but not soggy—during the spring and summer when it is actively growing. This usually requires weekly waterings for indoor plants and more frequent waterings for those grown outside in warm environments. Regularly test the soil with your hand to dial in the right schedule. If the soil dries out, the fern’s foliage may quickly drop. During the fall and winter months, reduce watering to every other week, but make sure the fronds don't dry out during this period of dormancy.
Temperature and Humidity
Boston fern prefers temperatures between 65 and 75 F. They can’t tolerate extreme heat or extreme cold. Temperatures above 95 F can harm the plant, as can near-freezing temperatures below 35 F. This fern also thrives in humidity levels above 80 percent. You can mimic these conditions by setting your fern on a tray filled with water and pebbles and by providing a regular misting. In conditions of low humidity, the tips of your plan's fronds may turn brown. If this happens, use the recommendations above to up the moisture.
Boston fern is a low feeder, however, that doesn't mean it will thrive in poor soil conditions. For outdoor ferns, make sure you amend the soil with 1 inch of compost and mulch annually to maintain good growing conditions. Indoor ferns should be fed once a month during the spring and summer using a 20-10-20 liquid houseplant fertilizer at half strength. No fertilization is necessary during the late fall and winter months.
Types of Boston Fern
Boston fern comes in several varieties that each vary in appearance. Whether you opt for a dwarf variety, like the lemon button fern, or one with yellow fronds, the care still remains the same.
Here are some popular choices:
- Nephrolepis exaltata 'Compacta' is a short, compact, and upright version of the main Boston fern species. This type is sturdier than other varieties and will withstand a little heat and dryness.
- A medium-sized cultivar, Nephrolepis exaltata 'Florida Ruffle' has feathery, ruffled fronds which grow in a dense clump. This plant can be grown both indoors and out but thrives in an ultra-humid environment.
- Nephrolepis exaltata 'Golden Boston' yields golden leaves and can be grown outside in a pot, and then overwintered indoors to be relocated outside again the next season. This variety is considered low-maintenance and makes a wonderful air purifier for the home.
- Similar to 'Golden Boston,' Nephrolepis exaltata 'Rita's Gold' also grows yellow, almost chartreuse, fronds. It shimmers in the sunlight and compliments impatiens and begonias in a container setting.
- Nephrolepis exaltata 'Fluffy Duffy' is a small, dense, and finely textured fern. This variety's feathery fronds look great in hanging baskets, and it benefits from a daily misting year-round.
Boston fern responds well to drastic pruning, as this practice encourages bushy growth and can correct issues of legginess. The best time to prune an indoor plant is when you're ready to repot it. Simply remove all browning leaves and clip back leafless runners. Next, give your fern a good haircut by trimming off the side fronds at the base with sharp shears. Don't crop the top the plant, but rather trim around the edges to your desired shape.
Outdoor plants can be cropped to four inches above the ground to overwinter. They may gradually put out new growth in the winter but will flourish come spring.
Propagating Boston Fern
Boston fern is very easy to propagate by division. In fact, this is a great method to use for a fern that has outgrown its pot or is taking over a garden space.
Here's how to propagate Boston fern by division:
- Gather a sharp pair of garden shears, a garden trowel (for indoor plants), a spade shovel (for outdoor plants), a pot, and potting soil (for indoor plants only).
- In the spring, carefully separate a section of your fern with healthy roots attached. You can use a garden trowel to separate indoor plants, and a spade shovel to carefully pull apart outdoor plants. (Note: Even small sections can become established new plants with proper care.)
- Fill a pot halfway full with potting soil (for indoor plants) or dig a new hole in the garden (for outdoor plants).
- Plant your division into either the mix or the ground, taking care to fully cover the roots when you backfill the hole with soil.
- Water the new division, and keep the soil lightly moist at all times. Keep indoor plants in a warm spot away from drafts and temperature fluctuations, and out of direct sunlight.
- After a few weeks, gently pull on the base of the fronds. If you feel resistance, you know your fern has taken root.
How to Grow Boston Fern From Seed
Like all ferns, Boston fern does not generate seeds. Instead, ferns are grown from spores collected from adult plants. You can also purchase fern spores from a garden store.
Here's how to grow Boston fern from spores:
- Gather a sheet of paper, a jar, potting soil, and pots (for indoor plants), or compost and peat (for outdoor plants).
- Hold your paper under the fronds of an adult fern. Shake the fronds gently to help spores fall from the underside of the leaves.
- Collect the spores in a jar and select a warm area for planting.
- Prepare your pot with potting soil or prep an outdoor area with a mixture of compost and peat.
- Wet the soil and broadcast the spores over the surface of the pot or the garden plot. Mist or gently water the soil to keep it moist at all times.
- In about a week, check the pot or garden for a thin green haze (prothallia) that contains the sperm and the egg. Continue misting to hasten fertilization.
- Mist frequently until you see the prothallia sprout, and then water the seedlings on a regular schedule to maintain moist soil conditions.
Potting and Repotting Boston Fern
Boston fern prefers containers that take longer to dry out. like plastic or glazed terracotta pots with ample drainage holes. Repotting is best done in the spring, once you see roots poking out of the soil. Select a pot size that is slightly larger than the plant's root ball, or size up your pot by 2 inches. Gently remove the fern from its old pot, and replant it at the same depth using a fresh potting mix. Take care to bury all the roots, and then give your fern a good drink of water. Place your pot in a warm area in your home, out of direct sunlight.
Foxtail fern goes through a period of dormancy in the winter, so some gardeners prefer to bring their potted fern indoors. However, trying to continue its growing cycle indoors often results in a smattering of brown fronds on the carpet. Instead, cut your potted plant back to 4 inches above the soil and store it in a cool, dry area, like a basement or garage. Water your fern once a month until spring, and then relocate it outside for a few hours each day, once outdoor temperatures warm up.
For garden ferns, perform a late fall cutback and withhold fertilization. Spread a thin layer of compost and mulch at the base of the plant and water it throughout the winter, as needed, to keep the soil barely moist.
Common Pests & Plant Diseases
A Boston fern grown outside can become a target for whiteflies, mealybugs, and chewing insects, like snails, slugs, and caterpillars. Whiteflies can be found on the undersides of leaves where they suck the plant's juices and leave behind a sticky mold. Similar symptoms present for a mealybug infestation. Chewing insects will leave behind a slimy trail and cause holes in the leaves.
Whiteflies are best controlled by reducing the population with several blasts from the garden hose. This may take a couple of treatments. Mealybugs can be spot treated with a diluted solution of isopropyl alcohol. Run a test spot to make sure your solution isn't strong enough to burn the plant's leaves. Slugs, snails, and caterpillars can be controlled by handpicking or by providing a rough surface around the plant to deter mollusks. This can be accomplished by sprinkling gravel, crushed eggshells, or coffee grounds at the base of the plant.
Indoor and outdoor ferns can also suffer from blight, a fungal infection that will leave the plant covered in a brow web-like mycelium. This condition can be treated naturally by simply repotting the plant in a sterile container and discarding the diseased soil in the process. Only treat your plant with a fungicide when all other methods have failed.
Common Problems With Boston Fern
Overwatering your Boston fern can result in root rot, which causes your fern's fronds to turn grey and its roots to brown. Repotting and discarding the diseased soil is the best treatment for this problem. Root rot can also be prevented by providing ample drainage and airflow to the fern's roots.
How does Boston fern help your home environment?
Boston fern is said to be one of the best air-purifying houseplants. It helps to rid the indoor air of toxins, like formaldehyde, plastic off-gassing, and cigarette smoke. This plant also restores moisture to dry air, potentially helping with conditions like dry skin, and dry noses and throats.
How did Boston fern get it's name?
This variety of fern was first discovered in a lot of fern plants shipped from Philadelphia to Cambridge, Massachusetts in 1894. Subsequently, the Massachusetts-based distributor started propagating this cultivar for sale, making it a popular houseplant.
Where should I hang my Boston fern?
Since Boston ferns naturally grow in sub-tropical areas, a humid bathroom with indirect sunlight provides the perfect habitat for this plant. Ferns also do well in a bright bedroom, where they detoxify the air as you sleep.