Nephrolepis exaltata is the classic hanging-basket fern, with long arching fronds made up of hundreds of small leaflets.
It has a reputation for being difficult, which is not quite fair. It needs one thing most homes do not provide, and once you provide it the plant is straightforward.
Light
Nephrolepis exaltata grows best in medium indirect light. Under a forest canopy it never sees direct sun, and it does not tolerate it indoors either.
Too much light
Fronds bleach, then go crisp and brown.
Too little light
Growth slows and the plant thins out, but it copes better than most.
Watering
Keep the soil consistently moist. Unlike almost every other plant on this site, letting a Boston Fern dry out completely usually kills the fronds that were open at the time.
Water when the surface starts to feel dry, not when it is dry through.
On average:
- Spring & summer: two or three times a week
- Autumn & winter: once or twice a week
Signs of overwatering
- Fronds yellow and go limp
- Soil smells sour
- Crown goes soft and black
Signs of underwatering
- Leaflets go crisp and drop in numbers
- Fronds go pale and papery
Humidity is the whole job
Below about 50% humidity the leaflets brown and shed, and no amount of watering compensates. This is the single reason Boston Ferns fail indoors.
A bathroom with a window is the natural home for one. Otherwise run a humidifier nearby or group it closely with other plants. Misting does not work, because the effect lasts minutes.
Keep it between 16°C and 24°C (61-75°F). It dislikes heat as much as dry air, so keep it away from radiators.
Soil and repotting
Soil
A moisture-retentive mix, peat or coco coir with perlite, that holds water without turning to mud.
Repotting
Every year or two in spring. The roots fill a pot quickly.
This is also when to divide. A large fern pulls apart into several plants, each with a section of crown and roots.
Feeding
Half-strength balanced fertiliser once a month through spring and summer. Ferns are sensitive to fertiliser salts, so underfeed rather than overfeed.
Pruning and grooming
Cut brown or bare fronds right down at the base. Do not trim individual leaflets off a frond, because the frond will not fill back in.
A neglected fern can be cut back completely, to about 5cm (2 inches) above the soil. Keep it moist and humid and it regrows from the crown within a few weeks.
Common problems
Leaflets dropping everywhere
Dry air. The most common complaint and it has one fix.
Brown, crispy frond tips
Also dry air, or minerals from tap water.
Yellow limp fronds
Overwatering, or a pot that does not drain.
Whole plant looking thin and sparse
Not enough light, or it needs dividing and repotting.