Ferns are members of a particular group of vascular plants that don’t produce seeds and flowers to reproduce. Instead, ferns reproduce through the production of spores.
They are what are known as ‘vascular’ plants and contain uniquely formed tissues that conduct water and nutrients.
Fern leaves are known as fronds and are composed of a stalk consisting of a blade and petiole.
The main axis of the blade is called the midrib and the tip of the frond is known as the apex.
The exact shape, size, and texture of fronds are different for different species of fern. There are more than 20,000 different types of fern species known.
They are a great choice of plant for shaded areas that can be tough to fill.
Ferns are perennial, grow quickly, and are easy to propagate. Due to the wide variety of different ferns available, you can add lots of different shapes and textures to your garden to add interest.
When placed indoors, ferns can provide lush greenery and can be a stunning addition to hanging baskets or pots.
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Why are the leaves of my fern curling up?
Curling fronds can be caused by a variety of different factors. In order to treat the problem properly, you must first determine the cause of it. Too much water or low levels of humidity can cause the fronds on your fern to curl up, as can a number of different pests and diseases that can strike your plant. Ferns like shaded areas, so direct sunlight and too much heat can also cause them to suffer. While they enjoy damp conditions and nutrient-rich acidic soil, ferns are also susceptible to damage from excessive amounts of fertilizer or from soil that is not free-draining. A number of pests can also attach themselves to ferns – particularly if the plants are not in the best of health.
Dehydration
Your fern leaves curling up could be a sign that it is dehydrated and needs water.
Different types of fern require a different level of water so you will need to check the care guide for your particular plant.
But, in general, ferns like a moist environment that somehow reflects their natural habitat.
Check the soil and make sure your fern is not in direct sunlight.
Too much water
Too much water can also cause the leaves of your fern to curl up. Although they like plenty of moisture, ferns also require free-draining soil.
Failure to provide adequate drainage can quickly lead to root rot which can seriously harm your fern, or even kill it.
When root rot sets in your plant will quickly start to look unwell as it will not be receiving the correct amount of nutrients.
Low humidity
Ferns are jungle-dwellers and require moisture and humidity to thrive. If the air around them is too dry, the leaves of your plants will curl up and the tips will turn brown.
This can be as a result of living in a low humidity area but other factors can play their part too.
Central heating and HVAC systems can dry out the air in a home or office and cause your plant to suffer.
Too much sunlight
In their natural environment, ferns grow under tree canopies and receive indirect sunlight and plenty of shade.
If your fern is placed in direct sunlight, it is likely to become stressed by the heat and this can cause its leaves to curl.
Too much sun can also dry out the soil quicker than expected which will starve your fern of much-needed water. Most ferns do not cope well in dry soil.
Too much fertilizer
You can have too much of a good thing. Leaves of plants that are exposed to excessive amounts of fertilizer will curl up and turn brown due to a build-up of salts in the soil.
Too much fertilizer can also scorch the roots of plants and as the roots of ferns are particularly fragile, they are susceptible to this.
This is a common problem in potted ferns which don’t receive adequate drainage. It can also occur as a result of being overzealous with fertilizer.
When fertilizing potted ferns, you should use a standard houseplant fertilizer diluted to around half.
Wrong Soil Type
Due to their natural habitat, ferns demand soil that is rich in nutrients.
Fertilizing according to the instructions for your plant is recommended as too little fertilizer will stunt the growth of your plant.
Ferns tend to prefer acidic soil so a pH between 4.0 and 6.0 is usually best. When planted directly in the ground, ferns will thrive in organic matter-rich soil.
As always, there are exceptions to this rule so it’s important to check the ideal conditions for each plant before you buy it.
Pests & diseases
Ferns are generally quite hardy when it comes to pests and many common pests don’t tend to cause them too many problems. That said, scale can be attracted to ferns.
Scale is a sap-sucking insect that will leave a sticky substance on the underside of the leaves and cause them to curl. Other pests will affect ferns if they are not properly cared for.
The same is true of fungi and bacterial infections. Plants that are not kept in their ideal conditions will not be at optimum health and so will find it difficult to fight off these types of infections.
Phosphorous deficiency
Plants require phosphorous to grow and thrive. If they are not receiving it in sufficient quantities, the leaves will begin to curl up and go dry.
Phosphorous deficiency tends to manifest itself in the older, lower leaves first and then move up the plant.
If you see signs of leaf curl on the lower leaves, it is best to act soon to prevent the problem from getting worse.
Nitrogen deficiency
Getting the balance of nutrients right is important in caring for ferns.
Adding phosphorous-rich material can lead to a deficiency in nitrogen. If you have added phosphorous to the soil and the lower leaves are still curling, your plant may be suffering from a lack of nitrogen.
Solutions to counter curly leaves on ferns
Appropriate watering
Ferns are thirsty plants that need to be watered regularly. But they require free-draining soil to prevent sitting water from damaging their roots and causing root rot.
Once the roots start to rot, not only will the disease spread, but your fern will not be able to take up the amount of water required to keep it healthy.
Root rot can be difficult to spot but an early sign will be curling leaves.
If the leaves are curling and the soil is wet, it is worth removing the plant from its pot and examining the leaves. Any rotten roots will need to be removed.
The plant will then need to be repotted in fresh soil.
You can help guard against root rot by placing a layer of gravel or stones in the base of the pot before adding the soil and making sure the pot has plenty of drainage holes.
If your fern is planted directly in the ground, adding sand or bulky organic matter to the soil will aid drainage.
Increase humidity
Ferns love humidity and in their natural environment, many of them thrive in humidity levels of around 70%.
They will cope with lower humidity but ideally like levels to be above 40%. This can be a problem when keeping ferns in the house as, for most homes, 40% would be considered at the top end of the humidity scale.
To address this problem, you can place a tray of pebbles or stones at the base of your plant to increase the humidity levels surrounding the fern.
That way, when you water it, the water that drains through will gather in the pebble tray, and as the temperature rises, the pebbles will heat up and the water will evaporate to increase humidity.
If you prefer, you can buy a humidifier to regulate the humidity of your plants.
Appropriate sunlight
All plants need sunlight. But, the right amount is determined by their natural habitat.
Ferns tend to grow naturally in a shaded area so the location of your plant should replicate this.
Your fern should not be placed in direct sunlight or by a window where the sunlight will be magnified.
If the leaves on your fern begin to curl and you think it may be a result of too much sun, you should move it immediately.
Flush out excess fertilizer
If your fern is suffering from leaf tip burn and curling edges, you will need to flush out the excessive salts which are causing the problem.
If you plant the fern outside directly in the ground, a good soaking will do the trick. Of course, if your soil does not drain easily, you may need to dig in some sand prior to watering.
For ferns planted in pots, there are two options when it comes to flushing out salts.
You can either place the plants outside if they are not already there and give them a thorough soaking with a hose.
You can fill a basin with water and place your potted plant in it, making sure the soil is fully submerged. Leave it there for 2 hours, remove the pot, and allow it to drain fully.
Do not apply fertilizer again for at least two weeks, and only after you have seen an improvement in the health of your plant.
Check the acidity of your soil
While some plants can cope with a variety of soil types, ferns can be quite discerning when it comes to their preferred level of acidity or alkaline.
Find out the correct pH level for your plant using a pH test available from any gardening center and then take the appropriate steps to increase or decrease the acidity level of your soil as required.
Treating pests in ferns
Scale is a sap-sucking insect that can cause significant damage to your fern if not dealt with. Small infestations of scale can be treated with rubbing alcohol.
Scale usually attaches itself to the underside of leaves and you will need to apply the alcohol directly to the scale to get rid of the infestation.
For larger infestations or if the rubbing alcohol does not solve the problem, try a standard insecticide available from the garden center or hardware store.
Ferns are not generally susceptible to many common pests but you should still examine the underside of the leaves as part of your routine maintenance schedule and deal with any issues.
Many pests can be easily removed using warm soapy water if you spot them soon enough.
Check the condition of your soil
Phosphorous deficiency can be caused by fluctuations in temperature which make it difficult for your plant to take in this vital nutrient.
To prevent this, try to keep the temperature consistent.
If your ferns are planted in the ground, you can try adding bonemeal which is rich in phosphorous and is easily taken up by plants. Another option is chopped-up banana skins.
If your fern is suffering from a lack of nitrogen, a fish tankage fertilizer will provide the boost it needs.
Frequently asked questions about Fern leaves curling
Should I mist my fern to stop the leaves curling?
Misting can help broad-leaf ferns maintain strong and can be applied daily if required. It’s not recommended for crinkle-leaf ferns as they will hold on to the water which can lead to rot or fungal infections.
Is the pot I’m using causing my fern leaves to curl?
It could be. A pot that is too big is likely to hold on to too much water which could be damaging the roots. You should use a shallow, plastic pot with good drainage. Clay pots can dry the soil too quickly, particularly when it’s hot.
Daniel has been a plant enthusiast for over 20 years. He owns hundreds of houseplants and prepares for the chili growing seasons yearly with great anticipation. His favorite plants are plant species in the Araceae family, such as Monstera, Philodendron, and Anthurium. He also loves gardening and is growing hot peppers, tomatoes, and many more vegetables.