What Are the Causes of Yellowing Fronds on Indoor Ferns?

Moisture

• In its natural habitat under dense tropical forest canopy, ferns enjoy lots of moisture and humidity. But too much water can cause of yellowing fronds. Yellow fronds eventually wilt and the plant could succumb to rot and fungal diseases. Poor drainage and standing water can create this problem. Too little moisture can also cause the leaves to turn yellow and fall off the plant. There are many factors that affect the moisture levels in an indoor growing environment, so the best rule for watering is to test soil moisture with a finger. The Boston fern and holly fern should be watered after the soil has dried out a bit.. The button and maidenhair fern, on the other hand, need constant moisture to thrive.

Humidity

• When the interior leaves of a fern turn yellow and drop, it may be a sign that humidity is too low. Low humidity can also cause the plant tips and fronds to turn brown and dry. The best humidity level is 40 to 50 percent, although ferns can tolerate levels as low as 30 percent. Homes average around 10 to 15 percent. For this reason, ferns grow nicely in bathrooms, where humidity tends to be higher. Using a humidifier or adding a pan of water to the room can help raise humidity.

Light

• As a general rule, if plants are not getting enough light, their leaves may turn yellow and die. In the case of a fern plant, this is unlikely because it needs very little light to thrive. The fern should be placed some distance away from direct sunlight. Too much light can scald the leaves. A north- or east-facing window works well. If sunlight is too harsh on the plant, a sheer curtain can help darken things a bit.

Diseases

• Root rot is a common condition in ferns that are over watered or allowed to sit in water. Symptoms include wilting, yellowing leaves and a stunted plant. Fronds may also turn gray. To avoid this condition, which causes the roots to rot away, limit watering and ensure both soil and container are clear of the fungus. Fungicides may also prove helpful if the fungus has take control of the a fern. Ensure drainage is adequate and avoid planting in containers that hold standing water at the base.