Ferns are my go-to anytime I want to add forest vibes to an indoor space. A Boston or maidenhair fern is such a gorgeous way to capture the woodland feel.
And with an enormous variety of different species available, there’s a fern for pretty much any growing environment – indoors or out.
These plants grow on every continent but Antarctica and in all USDA Hardiness Zones from 1 to 13, from the dry desert to the icy mountaintops.
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Since they grow in such a diverse range of habitats, there isn’t a “one-size-fits-all” approach to growing ferns.
But whether you are cultivating them indoors or out in the landscape, all ferns need nutrients, and that means more than likely you’ll need to fertilize them at some point.
An underfed specimen isn’t going to grow well or look its best. It might even die.
I remember my very first maidenhair houseplant. I had heard how temperamental these plants are and I babied the heck out of that thing. I swear if I’d had to massage the fronds to keep it healthy, I would have!
That’s when I realized what a difference fertilizing really makes. With careful feeding, I had one happy plant.
In this guide, we’re going to discuss everything you need to know about how to fertilize your ferns to keep them happy and thriving.
Here’s what I’ll cover:
Keep in mind that there are dozens of ferns that we grow as houseplants and they differ in their nutritional and environmental needs.
What an epiphytic staghorn (Platycerium spp.) requires is much different from what a cool-weather-loving holly fern (Cyrtomium falcatum) wants.
So there’s no one method of caring for such a diverse range of plants. Most of the types that we grow indoors come from tropical or sub-tropical regions and have fairly similar needs.
The advice in this guide applies to the most common species, like American maidenhair (Adiantum pedatum), bird’s nest (Asplenium spp.), Japanese painted (Athyrium niponicum), crocodile (Microsorum musifolium), Boston (Nephrolepis exaltata), button (Pellaea rotundifolia), and rabbit’s foot (Davallia fejeensis).
Most of these prefer moderate temperatures and moisture.
If you have a rare type or one that comes from a desert or extremely cold climate, double check the specific needs of the species before feeding.
Why You Should Fertilize
Container plants rely on us gardeners for all of their food and water requirements. They can’t access what they need in the environment as they could if they were growing outdoors.
Underfed specimens will be stunted, might turn yellow, and could even die.
When fed appropriately, the plants will grow lush foliage, and will be robust enough to fight off potential pest or disease problems.
Many potting mediums will contain some slow-release nutrients, so you might not need to feed right away after repotting. But over time, these nutrients leach out and you need to supplement with fertilizer.
In addition to supplying adequate fertilizer, it’s recommended that you repot your indoor ferns regularly, to refresh the potting soil even if you don’t need to increase the size of the container.
When to Feed
Ferns are relatively light feeders. In general, species that thrive in sunny conditions will need more frequent feeding than those that grow in dark conditions.
That’s because those growing in the shade photosynthesize far more slowly and need less energy than those in the sun.
Feed your potted plants once a month during the spring and summer using a mild, balanced fertilizer or a product that has a slightly higher ratio of nitrogen compared to potassium and phosphorus. We talk more about this in the next section.
It’s best to avoid feeding in the winter because that’s when most are growing very slowly or even partially dormant.
We don’t want to be encouraging new growth when they’re storing up energy for next season’s growth spurt.
However, if you fear that your plant is seriously depleted, go ahead and feed whenever you need to.
I’ve inherited ferns that I strongly suspected hadn’t been fed in years, if ever. I decided it was better to feed in the winter than wait until spring.
What Type of Fertilizer to Use
As mentioned, a mild, balanced food or one with a slightly higher ratio of nitrogen is ideal.
I prefer feeding using a liquid soil fertilizer, but pellets are fine, too. Avoid using foliar food because many ferns are sensitive to this type of fertilizer and it can burn the fronds.
You can tell if a fertilizer is balanced or high in nitrogen by looking at the NPK ratio, which will be printed on the label.
NPK stands for nitrogen (N), phosphorus (P), and potassium (K) – the major macronutrients – and the numbers tell you the ratio of each nutrient in that particular product.
You want something like 1-1-1, 2-2-2, 3-3-3, 3-2-1, or similar. A product with an NPK ratio above 10-10-10 is too strong and should be diluted by half.
I generally avoid fertilizers made from stinky materials like fish meal or blood meal when feeding indoor plants, just because it will smell pretty ripe for a while until it breaks down.
My go-to fertilizer for ferns and many other houseplants is Dr. Earth’s Pump and Grow.
This is a general-purpose fertilizer made out of waste food scraps from grocery stores and the pump bottle is super handy.
It has a NPK ratio of 1-1-1 which is perfect for feeding your indoor specimens.
Dr. Earth Pump and Grow
Snag yours at Arbico Organics in a 16-ounce bottle.
Down to Earth’s Bio-Live has a NPK ratio of 5-4-2, which is perfect for ferns with its slightly higher nitrogen content.
Plus, this product contains beneficial bacteria and mycorrhizae to create a healthy growing environment.
Down to Earth Bio-Live
Pick some up at Arbico Organics in five-, 25-, or 50-pound boxes.
Feed for Fabulous Foliage
Although they are not particularly demanding, providing your ferns with supplemental nutrition in the form of fertilizer helps to ensure they have everything they need to thrive.
What types are you growing? Let us know if you’re a painted fern lover or a Boston fan through and through in the comments.
Don’t stop now! Learn more about the fabulous world of ferns in the following guides:
