Why Are My Heart Fern Leaves Turning Yellow?

It’s easy to find yourself bombarded with information on heart ferns (Hemionitis arifolia) when searching for tips on how to keep them healthy. Their popularity has endured seemingly forever among plant enthusiasts, and it’s easy to see why.

The shape of these delightful botanicals is remarkably similar to the object from which they get their name, and their sturdy, green leaves are in a class by themselves.

Ideal as a focal point for a sunroom, windowsill, garden, or terrarium, they bring life to any area in which they are placed.

Why Are My Heart Fern Leaves Turning Yellow?
Photo by Yercaud-elango, CC BY-SA 4.0

However, you may be wondering what to do if you notice signs of yellowing leaves on your otherwise lovely heart ferns.

The following information is designed to help you understand why this may occur and get ahead of the curve in the race to save them from certain doom.

Why Do Heart Ferns Turn Yellow?

Yellowing leaves are often the result of overwatering and the collection of excess moisture. However, too little water, overusing fertilizer, and pest infestations can also cause this problem.

Balancing water, using proper fertilizer, and obliterating pest issues are your best defenses against the dreaded yellow phenomenon.

Heart Ferns Won’t Tolerate Saturated Soil

The most common reason for the yellowing of heart fern leaves is too much moisture. You may find yourself scratching your head, though, thinking that just two days ago, your ferns looked fine.

They probably did. It’s just that heart ferns won’t tolerate saturated conditions and will quickly deteriorate if exposed to waterlogged soil.

Unfortunately, your knee-jerk reaction may be to rush to them with the watering pail when you first notice the yellowing.

If you’re doing this, stop. If you’re not, resist the temptation. Instead, determine if excessive moisture is the problem or you’ll worsen the situation.

Push your finger into the soil to about half an inch depth. If you pull it out and there is soil clinging to the end of your finger even though you haven’t watered your ferns in days, a moisture problem is underway.

It is actually root rot that’s turning leaves yellow in this case, and the only remedy for this problem is to dry out the soil and use proper watering practices in the future.

Rescuing Your Heart Ferns from Moisture-Induced Root Rot

Save your ferns by removing them from the soggy soil and gently rinsing the roots.

Trim any dead areas away, discard the soil, wash the pots, and fill them with fresh, loamy soil. Replant your ferns, and then do the following to save them from further peril:

  • Keep your heart ferns out of dark locations; this encourages moisture to cling to the leaves.
  • Water evenly at the top and bottom, but avoid soaking the leaves or soil.
  • Water generously every seven days, or alternatively, water lightly every few days.
  • Let the soil dry out completely between waterings.

Stay Alert: Underwatering is Just as Deadly

Interestingly, underwatering is a close second to overwatering regarding the yellowing of heart fern leaves. In this case, the source of the yellowing is dehydration, and heart ferns don’t tolerate it well. Fortunately, your ferns might make a full recovery.

Even distribution of moisture is essential. It is somewhat like a cycle that moves from dry to very moist but must stay stringently within these parameters.

Dry, in this case, means that you can’t feel any moisture. It does not mean parched. If the soil feels more like thick dust, it’s arid.

Similarly, moist doesn’t mean soggy; it means merely mildly wet.

If you’ve determined that your ferns are dehydrated, you can give them a thorough watering, provided you avoid overdoing it in the future.

In other words, don’t end up too far on the other side of the ditch and start overwatering your heart ferns. 

Prevent Dry Soil Problems in the Future

If your heart ferns survived a cycle of underwatering, consider yourself lucky.

However, don’t take for granted that they are out of the woods until you once again have thriving, green ferns.

Follow these simple tips to prevent the same catastrophe from reoccurring:

  • Water your ferns until water drips from the drainage holes in the pot.
  • Avoid placing your ferns in excessive direct sunlight.
  • Water evenly to avoid leaving dry pockets that could cause certain root sections to die.
  • Consider using a humidifier if the air in your home is particularly dry.
  • Touch the soil daily to ensure it’s adequately moist between waterings.

Additional Considerations

Although overwatering and overly dry soil are by far the most common causes of yellow heart fern leaves, using fertilizer to excess and pest infestations may also be culprits.

Excessive Use of Fertilizer

If you think you’re on track with proper watering techniques but are using a lot of fertilizer, this may be the source of the problem.

If you’ve been overzealous with fertilizer, dilute what you’re using to approximately half. Any standard house plant fertilizer is usually safe for heart ferns, but not when overused.

You may stop using fertilizer entirely for a season and see if you detect a notable difference. If your ferns seem just as healthy without it, consider erring on the side of caution, use high-quality soil, and forget the fertilizer.

Pest Infestations

Numerous insects, including spider mites, mealybugs, and scale insects, can wreak havoc on your heart ferns. In this case, the discoloration may be yellowish-green.

A speckled, yellow-toned discoloration is a clear indicator of spider mites. If you carefully lift the leaves, you may see tiny webs. If this is the case, look no further. Spider mites are your problem.  

Unfortunately, however, heart ferns are easily damaged by many pesticides. Therefore, it’s in your plants’ best interest to use a natural pesticide instead.

One of the best is simple neem oil, which is easily acquired. Soak a cotton ball or swab in the oil and apply a light coat to the leaves. It should begin working in about 24 hours to kill off various pests without harming your ferns.

Also read: Why Are My Heart Fern Leaves Curling?

Author: Stanislav Lem


Stanislav Lem is the founder of Big Time Living, where he provides tips for gardening, traveling and lifestyle. Stan is an entrepreneur, journalist and traveler.
His mission is to provide information to help people become better planters, travel more and live a happy life. His blog has been featured on Huffpost, Yahoo and MSN.