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8 Typical Mistakes That Cause Fern Leaves to Curl Up (How To Fix It)

Ferns are truly captivating, aren’t they? Take the staghorn fern, for example—it’s a perfect showcase of nature’s vast diversity. However, as with all plants, they come with their own set of challenges.

The main culprits behind fern leaves curling include overwatering, insufficient humidity, underwatering, and pests. To remedy curled leaves, make sure to water your ferns only when the top inch of the soil feels dry and aim to maintain a humidity level of 60-70%. Keep an eye on your plant’s health, too, and act quickly if you spot any signs of pests or diseases.

1. Overwatering

fern leaves curling

The leaves of the fern have curled due to overwatering.

Ferns thrive in a moist atmosphere, but when you bring them indoors, there’s a real risk of giving them too much water, which can lead to root rot.

If the roots fail to deliver water to the upper parts, you’ll notice the leaves beginning to curl and turn yellow. In conditions where the temperature is high and humidity low, the leaf tips might brown and get crispy.

Here’s what you can do:

  1. Gently take the fern out of its pot to check the roots.
  2. If you find any rot, rinse the roots, and trim away the damaged sections.
  3. Clean the cuts with hydrogen peroxide to disinfect.
  4. Repot the fern in fresh, well-draining, sterile soil.
  5. Water the fern only when the soil’s top inch has dried out.
  6. Always opt for pots with drainage holes to avoid waterlogging.

2. Too Dry Air

fern leaves curling

The leaves of the fern are curled because of the dry air.

The moisture in the air is crucial for ferns, which naturally flourish in the damp shadows of forests, surrounded by high humidity levels.

When ferns are placed in a room with dry air, their fronds start to curl up at the tips. The smaller leaf sections might also curl, and turn yellow or brown. This is the fern’s way of reducing moisture loss.

Here’s what you can do:

  1. Gently prune away the dry fronds.
  2. Aim to maintain humidity levels around 60-70% near your fern.
  3. Group your houseplants together, which helps keep moisture in the air around them for longer.
  4. Consider using a humidifier if necessary.

3. Underwatering

fern leaves curling

The leaves of the fern have curled up due to dehydration.

As previously noted, ferns are lovers of water and humidity, hardly bearing drought and insufficient watering well. During hot and dry spells, soil, particularly in pots outdoors, can dry up rapidly.

While some fern varieties may withstand dry periods better than others, they all generally need consistent moisture. If the pot’s soil dries out almost entirely, the fern will start experiencing water shortage, leading to its leaves curling and wilting from the tips. Leaflets may drop off swiftly, though the fronds might hang on a little longer.

Here’s what you can do:

  1. Water the fern generously, ensuring any excess can freely drain away.
  2. Water the plant when the top 1 to 2 inches of potting soil feels dry.
  3. For convenience, consider using a soil moisture meter.
  4. Pay extra attention to the soil’s moisture level, especially during summer months.
  5. Cut back on watering during the colder winter months.

4. Direct Sun

fern leaves curling

The leaves of the fern are curled because of the direct sun.

Large trees not only provide ferns with the high humidity they thrive in but also the shade they prefer. This is why ferns are known for their love of shady environments, and to grow them successfully indoors, we need to mimic these natural conditions as closely as possible.

Direct sunlight can be harmful to ferns, causing their leaves to burn and curl. The burn marks may appear brown or black, varying with the sun’s intensity.

Here’s what you can do:

  1. Relocate the fern to an area with more shade.
  2. Trim away any severely damaged leaflets, as they won’t recover.
  3. Adjust the plant’s location experimentally to gauge the exact amount of light it needs, shifting it between brighter and dimmer spots until you find the ideal location.
  4. When introducing a new plant, gradually acclimate it to brighter conditions to avoid shock.

5. Soil Issues

Poorly drained soil

The leaves of the fern are curled because of poorly drained soil.

The health of a plant is closely tied to the quality of its soil. Soil that stays wet for too long can lead to root rot, causing the leaves to curl.

Another critical aspect is the nutrient levels in the soil. Soil with a high pH can lock away essential nutrients like nitrogen and iron, making them inaccessible to the plant. This nutrient deficiency can lead to chlorosis, characterized by the yellowing and curling of leaves.

Here’s what you can do:

  1. If the soil doesn’t drain well, replant the fern in better-draining soil.
  2. Test the soil’s pH level.
  3. Should the pH exceed 7.0, work to lower it and make the soil more acidic.
  4. Follow up by applying a slow-release fertilizer that includes nitrogen, phosphorus, and potassium to nourish your fern.

6. Overfertilization

Just as a lack of nutrients can be harmful, an excess can also negatively affect a fern’s health. Applying fertilizer too frequently can lead to the accumulation of salts in the soil, which are harmful and can damage the roots.

Damage from excess fertilizer mirrors the effects of root rot, with leaves beginning to curl and turn yellow.

Here’s what you can do:

  1. Repot the fern in fresh, salt-free soil to give it a fresh start.
  2. Limit fertilizing to no more than once a month to prevent nutrient overload.
  3. Hold off on fertilizing during the winter and late fall when the plant’s growth slows down.

7. Insects

Pests

The leaves of the fern are curled because of the insects.

Insects pose a significant threat to plants. A small number of pests might not cause severe damage, but a large infestation will lead to leaves curling and turning yellow.

For ferns, scale insects are particularly harmful. They attach themselves to stems and leaves, feeding on the plant’s sap, and appear as white bumps.

Here’s what you can do:

  1. Manually remove any visible insects from the plant.
  2. Treat the fern with horticultural oil to deter pests.
  3. If the problem persists, apply insecticidal soap as a stronger measure against the infestation.

8. Fungus

Disease

The leaves of the fern have curled up due to disease.

Plants in the wild typically have a more robust immune system than those grown indoors. The indoor environment, often lacking in ventilation, creates conditions that are more conducive to the development of diseases. Ferns, like other houseplants, are susceptible to fungal or bacterial infections, with curling and browning of leaves being common symptoms.

Here’s what you can do:

  1. Start by removing the leaves that are most affected.
  2. Ensure the space where the fern is kept is well-aerated.
  3. Treat the plant with a fungicide that contains copper.
  4. Be careful not to overwater the ferns, as excess moisture can encourage disease.