Boston fern care: the classic fern houseplant

A Boston fern is the classic fern houseplant: it needs medium-bright indirect light, potting mix kept evenly moist, and more humidity than a heated US home usually offers. Get the humidity and watering steady and it grows into a full, arching plant; let it dry out once and it sheds leaflets all over the floor.

This card explains what makes Boston fern one of the more forgiving ferns, how to keep it through winter, and how to tell normal spore dots and runners from pests.

Boston fern and other common fern houseplants

Boston fern is a selection of the sword fern, Nephrolepis exaltata, native to tropical America. University of Wisconsin Extension notes that it is hardy outdoors only in USDA zones 9-11 and that it is the most drought tolerant of the commonly grown ferns. It does not flower; it spreads by runners and makes brown spore dots on the undersides of older fronds.

Clemson Extension's indoor ferns guide describes the main forms: 'Bostoniensis' with fronds cascading up to 3 ft, 'Compacta' at 15-18 inches, and 'Fluffy Ruffles' with compact, upright, frilly fronds. Wisconsin adds 'Dallas', 'Florida Ruffle', 'Golden Boston', 'Massii' and others.

Light

Wisconsin Extension recommends medium bright light, "such as in an east facing window or behind a sheer curtain in south and west windows." Clemson specifies bright indirect or filtered sun.

• East window: ideal.
• North window: works if the window is large and unobstructed; growth is slower.
• South or west window: use a sheer curtain or keep it a few feet back.
• Hanging baskets: often sit higher than the window frame and in shadow; check that the fern can actually see the sky.

Signs of too little light are sparse, stretched fronds; too much sun bleaches them pale. See houseplant light.

Watering a Boston fern

Keep the mix evenly moist but not saturated. In practice:

• Check by touch every 2-3 days. When the surface just starts to feel dry, water until it drains.
• Do not let the pot dry out completely; even one bone-dry episode can cause heavy leaflet drop.
• Never leave the pot standing in water; Clemson warns that standing water damages roots.
• Hanging baskets dry fastest; in summer they may need water daily.

If the pot is very hard to rewet, set it in a sink with 2-3 inches of water for 20 minutes, then drain. More detail: watering.

Humidity: the real challenge

Wisconsin Extension notes that ferns do best in humid environments, and that tips and edges of the leaflets brown in dry interiors, especially in winter. US homes with forced-air heat often sit at 20-30% humidity in January. What helps, roughly in order of effect:

1. A room humidifier set to 45-55%.
2. Moving it away from heat registers, radiators and drafty doors.
3. Grouping plants together.
4. Double-potting: Wisconsin and Clemson both describe setting the fern's pot inside a larger container lined with moist sphagnum moss.
5. A bathroom or kitchen with a bright window.

Misting feels useful but raises humidity only briefly. For a full explanation, see humidity for houseplants.

Temperature

Wisconsin gives a preferred night temperature of about 65°F and daytime highs below 95°F; Clemson suggests 68-72°F days and 50-55°F nights. In other words, normal room temperatures with a slight drop at night are fine. Move porch ferns indoors when nights reach the low 40s°F.

Soil and fertilizer

Use a mix that holds moisture but drains, such as a peat- or coir-based potting mix with some perlite. Wisconsin mentions peat and vermiculite mixes.

Fertilize lightly. Wisconsin recommends half-strength liquid or slow-release houseplant fertilizer every 4-6 weeks during active growth; Clemson suggests feeding monthly April to September at half rate and warns that heavy feeding scorches fronds. Feed little or not at all in winter. See fertilizer.

Repotting and dividing

Boston ferns fill pots quickly. Wisconsin suggests repotting or dividing every few years in spring by cutting the root ball vertically. Steps:

1. Water the day before.
2. Remove the fern and cut the root ball into 2-4 wedges with a serrated knife.
3. Pot each section at the same depth in fresh mix.
4. Trim damaged fronds and keep the divisions in bright shade and slightly more humid air for 2-3 weeks.

Runners that touch soil also root and can be cut off as new plants. Propagating from spores is slow and cultivars do not come true, so division is the practical method. See repotting.

Brown fronds and shedding: causes

Shedding of small leaflets is the most common complaint. Go through the list:

• Soil dried out in the last week or two: most likely cause.
• Dry air near a vent: brown tips and edges first, then shedding.
• Light change, for example after bringing a porch fern indoors.
• Fertilizer burn: crisp tips soon after feeding.
• Old fronds: the oldest fronds naturally yellow and die. Wisconsin notes that cutting old fronds at soil level encourages new ones.

See brown tips and dropping leaves for broader checklists.

Pests, and what is not a pest

Wisconsin lists scales and mealybugs as the main indoor pests; Clemson adds spider mites and warns that many pesticide sprays injure ferns, so test any product on one frond first. Rinsing the fern in a shower is often the gentlest first step.

Do not mistake spore dots for scale. Spore cases sit in neat rows on the underside of mature leaflets and are part of the plant. Scale insects are irregularly placed, sit on stems and both leaf surfaces, and can be flicked off. Details in scale insects and mealybugs.

Is Boston fern safe for pets?

Yes. The ASPCA lists Boston fern as non-toxic to cats and dogs. That makes it a popular hanging choice in homes with cats, though cats sometimes shred the fronds. If a pet eats a large amount and seems unwell, call your vet. See our pet-safe plants collection.

Seasonal care calendar

Bringing a porch fern indoors

Many US households buy Boston ferns as porch baskets and try to keep them through winter. It works best if you:

1. Move it in before the heat comes on, so it adjusts to indoor light while the air is still humid.
2. Hose it off outdoors and inspect for scale, mealybugs and slugs.
3. Cut it back by up to a third if it is huge; less foliage means less water loss in dry air.
4. Put it in the coolest bright spot you have, such as an east-facing bedroom or a bright unheated sunroom above 45°F.
5. Accept some shedding in the first weeks. New fronds formed indoors are adapted to indoor conditions.

Some growers simply treat porch ferns as annuals, which is reasonable if you have no bright, cool, humid spot indoors.

Buying a Boston fern

• Look for many new fiddleheads unrolling at the center.
• Avoid pots with brown, shedding centers, which suggests drying out in the store.
• Check the weight: a very light pot has been allowed to dry.
• Compact cultivars such as 'Compacta' or 'Fluffy Ruffles' fit tabletops better than full 'Bostoniensis' baskets.

Common mistakes

1. Misting instead of raising humidity. It feels like care but changes little.
2. Hanging it near the ceiling where heated air collects and the light is weaker.
3. Letting it dry out "a bit." Ferns are not succulents; one dry spell causes heavy shedding.
4. Overfeeding a struggling fern. Fertilizer burns roots already stressed by dry air.
5. Spraying it with an untested product. Many sprays injure fern fronds; test on one frond first.

Boston fern and indoor air

Boston fern often appears on lists of "air-purifying" houseplants, based largely on chamber studies. In real homes, the number of plants needed to measurably change air quality is far higher than anyone keeps; ventilation does much more. Grow it because it is beautiful and adds humidity around itself, not as an air filter. See air-purifying plants for the full picture.

What a fern does offer indoors is local humidity: a group of well-watered ferns and other leafy plants slightly raises moisture in the air right around them.

Is it worth it?

Boston fern is a good choice if you have an east window, run a humidifier in winter, or have a bright bathroom. If your home is very dry and you travel often, choose a Kimberly queen fern, a parlor palm or a spider plant for a similar soft, green look with less fuss.