Many ferns prefer conditions that limit where they can be grown. But containers allow for growing outdoor ferns in pots allowing you to enjoy an otherwise indoor fern outdoors.
Note that not all ferns are created equal, and some fare much better in containers than others.
By far, the most popular container fern is the Boston Fern (Nephrolepis exaltata), although Kimberly Queen ferns (Nephrolepis obliterata) are also quite popular.
Much of the information in this article will therefore be geared toward the Boston fern.
Still, you can apply it to any other container-friendly fern species by adjusting any necessary care requirements (such as the amount of water) to fit.
How To Care for Potted Ferns Outdoors?
Potted ferns need a little more attention than those planted in the ground because they have less access to the natural processes that ensure rich soil and proper drainage.
However, having a potted fern grown outdoors means you can have a healthier fern than one strictly indoors while being able to grow it as a perennial in areas where it will only survive as an annual.
The Benefit Of Potting Ferns
As mentioned, zone restrictions are perhaps the biggest reason to grow ferns in a container.
This allows you to bring them inside if the weather gets too warm or cold.
It also means you can shift the plants as needed if you live in an area where the direction of sunlight moves during the growing season.
Ferns are one of the most underrated homes and garden plants, yet they can grow in places most other plants can’t.
Choosing The Right Outdoor Spot
Ferns are known to be shade lovers, but this isn’t entirely true.
The ideal lighting for most ferns is dappled sunlight.
This means light that’s filtered through the leaves of other plants, allowing some bright patches that never stay focused on one part of the plant for too long.
However, you can also place the ferns in a spot that gets morning or evening sun with shade in the afternoon.
When picking a spot on your porch, patio, or deck, consider the lighting condition, as this is the single biggest factor in whether your fern will thrive, survive, or scorch.
The good news is that you can place Boston Ferns in hanging baskets, allowing you to give them some extra shelter under a porch or enclosed deck roof.
Fern Soil And Potting
Ferns love acidity, and many species will actually prefer a soil pH below 6.0.
This can kill most of your garden plants, but containers provide a lovely buffer zone to allow for plant combinations that wouldn’t otherwise work.
Additionally, your ferns need a lot of organic material that might prove too much for plants unless you separate them with containers.
Double Pots vs. Outdoor Humidity
Yet another advantage potted ferns have over ground-based ones is access to higher humidity levels.
Ferns love humidity and fare well in the kitchen or bathroom but aren’t always so happy in the garden where humidity is far less stable.
Potted ferns can bypass much of this problem, especially if you double-pot or use pebble trays.
Double potting is exactly as it sounds, with the potted plant sitting inside a second, slightly larger container.
Line the space between these containers with peat or sphagnum moss and add water to the moss when watering your fern.
The moss will absorb any excess draining from the inner pot and what you give it.
On top of that, the moss will dry out as the days go by, naturally increasing the humidity around your fern.
Watering An Outdoor Fern
Speaking of watering, the soak-and-dry method can save a lot of headaches when keeping an outdoor fern properly hydrated.
Most ferns are extremely sensitive to overwatering, and while it might seem rain overcomplicates the watering process, the soak and dry methods account for such variables.
Simply stick your finger into the soil to check the moisture levels.
Ferns will need to be watered when the soil is dry somewhere between ½” and 1 ½” inches down (depending on the species), with the Boston fern requiring water at an even 1” inch depth.
The space from the tip of your finger to the first knuckle is approximately 1” inch, making this process easy.
Likewise, you can mark a wooden chopstick or popsicle stick as a water sensor, although you’ll need to leave these in the soil for 20 minutes.
When you pull it out, the wood will be darker where water was present.
Always water slowly and evenly, careful not to get the fronds wet.
Work your way around the plant to help ensure one side doesn’t have more water than the other.
Stop when you see moisture seeping from the drainage holes, or the soil surface can no longer absorb as fast as you’re pouring.
Overwintering An Outdoor Potted Fern
Perhaps the greatest advantage of growing your potted fern outdoors is the ability to bring it inside when the temperature drops.
This means you can grow a fern outdoors in USDA zone 4 or 5 that normally wouldn’t survive as a perennial in anything colder than zone 9.
Make sure you’re keeping an eye on the temperature and bring it in if the forecast shows a big dip below your fern’s tolerance level for more than an hour or two.
Bring it inside if the forecast predicts a frost, damaging the plant permanently.
Before bringing the plant inside, give it a thorough spray-down to dislodge any pests.
Be sure to get the bottoms of the leaves where most pests tend to congregate.
Allow the plant to air dry a little and give it trim as needed.
Once you bring it inside, it’s best to quarantine the plant for a week or two to ensure it isn’t infested.
The overwintering process will be the same as if you’d grown the plant indoors all year.
It might have had an excellent growing season, so you may find it needs repotting the following spring if it becomes root-bound.
Bringing The Fern Back Outside
Once spring hits, it’s time to start preparing your fern to go back outside.
Keep an eye out for the final predicted frost so that you know when to move the plant.
At first, just bring it outside for an hour or two, then slowly increase its time outside each day until it’s ready to spend the rest of the spring and summer exclusively outside.
This process is called hardening and usually takes 1 to 2 weeks to complete, but it results in a much hardier plant for growing outdoor ferns in pots.