Watering Ferns the Right Way: Some Best Practices

large fern on a patio

By Erin Marissa Russell

Wondering about exactly how much water to give your ferns and how often they need it? We’ve got you covered with this guide that will tell you everything you need to know to grow lush, thriving ferns. Keep reading to learn exactly how to hydrate your fern plants—and you’ll also get some tips that can help make the watering routine easier.

How to Water Fern Plants

Ferns really flourish when they have access to a consistent and plentiful supply of water. After all, many of these plants come from the tropics, where rainfall is both ample and frequent, and humidity makes even the air a little damp. When they aren’t in the tropics, this supply of moisture must be provided from the gardener (although of course you’ll take rainfall into account when it hydrates ferns that are kept outdoors).

Keep your ferns happy by making sure that the soil where they’re growing stays damp. Although you should be shooting for soil that stays evenly moist, you don’t want it to be waterlogged or overly saturated. Whenever the surface of the soil is dry, you should water your fern plants again. Don’t let their soil dry out completely.

There are a few exceptions, ferns that don’t need consistently moist soil in order to thrive. These varieties include brake ferns (Pteris), holly ferns (Cyrtomium falcatum), and rabbit’s foot ferns (Phlebodium aureum). For these fern types, you should allow the soil to become slightly dry before watering the plants again. 

ferns on a porch

Tips for Watering Your Ferns

  • Avoid watering from above, which can cause the moisture to splash onto the leaves of your ferns. Instead, aim the water you give your ferns at the soil above their roots. It will trickle down into the root zone, where your ferns can absorb it and put it to use. These plants are only capable of absorbing water from the soil using their root network, so any that misses the soil and ends up on their foliage is wasted. 

    Water droplets that land on foliage will eventually evaporate, but until they do, they pose a risk to the health of your ferns. The sun can heat the water up until it burns the leaves of your ferns, causing sunscald damage. The extra moisture also contributes to overly wet conditions, which increase the likelihood that your plants will contract certain diseases, like root rot and other fungal illnesses. 
  • The exception to the above rule is when you’re misting a fern to add extra humidity to its environment. Misting the foliage of your fern imitates the conditions of the tropics where fern plants originate from. Placing a humidifier in the room where indoor ferns are growing is another good solution. Ferns may show they’re craving more humidity with brown discoloration at the ends of their leaves, or areas may die completely. The Boston fern, maidenhair fern, and staghorn are especially susceptible to damage when humidity in their environment is low. Holly ferns don’t need as much humidity as other plants in the fern category.

    A fern’s native habitat offers 70 percent humidity (or even more), while the modern home where a fern may be kept as a houseplant is normally closer to five or 10 percent humidity. Using a room humidifier increases the humidity in that room to between 30 and 50 percent. This is the lowest humidity level for ferns to stay healthy and keep growing. Although the plants can sometimes survive at lower humidity, they need 30 to 50 percent in order to really flourish.
  • Spots on the leaves of ferns you’re misting can occur if you use cold water. Water you give to plants (where you are providing hydration near the plant’s roots or misting its foliage with a spray bottle to increase humidity) should always be room temperature.
  • If temperatures in your area climb above 75 degrees Fahrenheit (24 degrees Celsius) or, if your ferns are kept indoors, whenever the room they’re in gets warmer than this, the plants will need you to water them more often. Not only is the extra needed to help keep your plants cool—you’ll also lose more of the water in the soil to evaporation due to the increased temperature.
  • If your ferns will be facing temperatures under 60 degrees Fahrenheit (15.5 degrees Celsius), they won’t need nearly as much water until things start heating up again. Only give them moisture in these conditions when the surface of the soil where they are growing is dry. (Don’t just make a visual determination—actually touch the soil to be sure.)
  • Know the signs of overwatering and underwatering so that if your plants start showing the symptoms, you can take action to adjust your hydration routine accordingly. Ferns that are getting too much water may cause yellowed foliage, wilting, or eventually, root problems or fungal diseases. Underwatering will cause your ferns to wilt. Boston ferns are especially likely to drop leaves when they don’t get enough water. Because both overwatering and underwatering can cause wilting, differentiate between the two by checking the moisture level of the soil. If wilting is happening while there’s moisture available to the plant in the soil, it must be due to overwatering.
  • If you’re having trouble keeping your ferns well hydrated, consider using a second pot to make more moisture available. Find a container to place underneath the one the plant is potted in (so the bottom container must be the same size as or larger than your plant’s container). 

    Add moist sphagnum moss to the bottom container, lining it completely. You’ll need to keep this moss evenly moist at all times, as it’s where your plant will draw its water from. 

    Plastic pots are your best option for the bottom container. You can use a clay pot as the one holding the fern, though— as long as the one it sits inside of is plastic. The porous nature of the clay will be a benefit, as the moisture from the moss in the plastic pot will be able to soak through the clay pot’s surface to reach the soil where the fern is growing. 
  • The rabbit’s foot fern, sometimes called the ball fern, (Phlebodium aureum) is vulnerable to salinity in their soil or water supply. It’s important to water rabbit’s foot ferns with soft water for this reason.

What About Watering Ferns with Epsom Salt?

If your ferns are planted in rich and healthy soil, it is not necessary to water them with epsom salt. However, if your ferns are not thriving and the leaves are turning yellow, then it’s possible that the soil of your ferns could be deficient in magnesium or sulfur. Epsom salt is approximately 13 percent sulfur and 10 percent magnesium, so it provides both of these nutrients and works as a fertilizer.

If your ferns are already healthy, it is not helpful and can harm them to over-fertilize by adding epsom salt. Ferns are relatively delicate and can be easily burned by too much fertilizer. How much do you add and how do you add it? The Epsom Salt Council recommends using two tablespoons per gallon of water as the correct mixture.

As you can see, it’s not quite as simple to make sure that ferns are getting just the right amount of water as it seems at first glance. However, as long as you provide a consistent level of moisture and take into account any specifics you’ve learned here that have to do with your particular variety of fern, you’ve got hydration mastered. Especially for the ferns that are sensitive to low humidity, an occasional misting goes a long way toward boosting their health as well.

As long as you handle the watering and misting, ferns are otherwise a generally low maintenance type of plant that doesn’t ask for much time and attention—though you’ll love how much a lush, healthy fern plant can beautify its environment in return for the care you provide.

Learn More About Watering Ferns Correctly

https://www.bbg.org/gardening/article/caring_for_ferns_as_houseplants

https://extension.uga.edu/publications/detail.html?number=B737&title=Growing%20Ferns

https://extension.umn.edu/houseplants/tropical-ferns

https://fairviewgardencenter.com/blog/front-porch-fern-tips/

https://homeguides.sfgate.com/water-fern-plant-63562.html

http://www.ladybug.uconn.edu/FactSheets/ferns.php

https://www.rhs.org.uk/advice/profile?pid=936

https://www.uaex.edu/yard-garden/resource-library/plant-week/boston-fern-11-18-05.aspx

http://www.uvm.edu/pss/ppp/articles/fernsin.html

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