Invasive Ferns Species You Should Avoid Planting Outdoors

Sometimes even potting these troublemakers can be problematic. 

Lygodium microphyllum at Jonathan Dickinson State Park
“Two decades ago, climbing ferns were exploding in South Florida. Thankfully, scenes like this are now rare, but it illustrates what can happen if Old World Climbing Fern (Lygodium microphyllum) is allowed to grow unchecked.” – Jennifer Possley. Photo: Photo by Sam Wright, Fairchild Tropical Botanic Garden

If you've never given much thought to your seasonal ferns aside from purchasing and watering, consider this the summer that all that changes. From the best indoor ferns to our top tips for keeping your fern green and thriving, it turns out, there's a whole lot to know about these Southern-porch favorites. But don't be fooled into thinking it's all good news. There are quite a few non-native fern varieties that experts like Jennifer Possley, conservation program manager at Fairchild Tropical Botanic Garden in Coral Gables, Florida, consider invasive—and you know that's one term a gardener never wants to hear. On a more positive note, there are things that you can do to help keep these invasive species in check, starting with being able to identify non-native species in your state.

According to Possley, invasive species are second only to development in the list of culprits contributing to biodiversity loss. "Non-native invasive species usually grow and spread very quickly, often much more quickly than our native species, which are growing in the geographic area where they evolved, complete with natural checks and balances," she says. It's a problem to be sure, but one that can be remedied or at least slowed with proper care. That means familiarizing yourself with the invasive fern species in your state and also planning your landscape carefully. "The best things you can do to support our fantastic plant heritage here in the South is to ensure that your landscape is dominated by native plants, keep a watch for anything that seems to be spreading aggressively, and nip weeds in the bud."

To get you started on the journey, Possley shares her list of most loathed invasive ferns.

Invasive Fern Species

01 of 08

Autumn Fern

Autumn fern
Steve Bender

(Dryopteris erythrosora)

You'll know this fern when you spot its copper fronds in the fall—a reason why it's so appealing to home gardeners. But don't let that glorious foliage fool you. "Recently, dense stands have been found to be naturalizing in north Georgia, and it is spreading in other states," says Possley.

02 of 08

Japanese Holly Fern

Japanese Holly fern
Artur Bogacki / Getty

(Cyrtomium falcatum)

As its name implies, the Japanese holly fern features dark green, holly-like leaves. It does well indoors, which is where Possley recommends it should stay in order to keep the spores from floating off and making themselves comfy elsewhere in your yard and beyond.

03 of 08

Mariana Maiden Fern

Maidenhair Fern
Naphatson Jansena / EyeEm / Getty

(Macrothelypteris torresiana)

Maidenhair ferns are beloved, but finicky. Keep these lacy fronds inside so you can enjoy their delicate appearance without fear of spread.

04 of 08

Climbing Fern

Lygodium microphyllum at Jonathan Dickinson State Park
“Two decades ago, climbing ferns were exploding in South Florida. Thankfully, scenes like this are now rare, but it illustrates what can happen if Old World Climbing Fern (Lygodium microphyllum) is allowed to grow unchecked.” – Jennifer Possley. Photo by Sam Wright, Fairchild Tropical Botanic Garden

Possley says climbing ferns are likely the most invasive fern species in the South. There are two varieties you'll find regionally: Japanese climbing fern (Lygodium japonicum) and Old World climbing fern (Lygodium microphyllum). The former is already widespread throughout the South and appears to be making its way northward. "Old World climbing fern (Lygodium microphyllum), is primarily restricted to peninsular Florida and it can literally engulf an entire stand of trees, eventually killing them," she says.

05 of 08

Non-native Sword Ferns

Close-up image of lush Ladder Fern (Nephrolepis exaltata) fronds, sword fern, Boston fern or fishbone fern

"The species Nephrolepis cordifolia and Nephrolepis brownii grow in dense stands and can cause major ecological damage," says Possley. Native sword ferns like giant sword fern (Nephrolepis biserrata), the popular Boston fern (Nephrolepis exaltata), and their cultivars (i.e., 'Macho fern' and 'Fluffy ruffles') are all fine to purchase, especially if you're buying from a garden center with extensive fern knowledge. "Be aware that many sword ferns are extremely challenging to tell apart from one another, so buy from a retailer that has staff proficient in plant identification (or better yet, a trained botanist!)," she says.

06 of 08

Wart Fern

Evergreen leaves of Wart fern of Hawaii

"My nemesis is the widely-used 'wart fern,' which may also go by the names 'serpent fern,' 'monarch fern,' or 'maile-scented fern,'" says Possley. "Wart fern is a terrible problem in Hawaii and is becoming one in peninsular Florida, where we increasingly find it in undisturbed habitat, far from landscaping." She advises avoiding Microsorum grossum, Phymatosorus scolopendria, and any combination of these names.

07 of 08

Staghorn Fern

Staghorn Fern
Andreas Hoernisch/Getty Images

(Platycerium bifurcatum)

While Possley says adding the staghorn fern to a list of invasive species likely won't make her any friends, the precaution is justified. She warns that they're becoming problematic in peninsular Florida, popping up in the tops of trees in natural areas where they are challenging to remove.

08 of 08

Water Spangles

Water Spangles

(Salvinia minima, Salvinia molesta)

"Water spangles is a tiny fern with big impact; colonies can completely cover the surface of still water, lowering dissolved oxygen and resulting in fish kills," says Possley. You can still appreciate its beauty by cultivating it in a pool that doesn't flow to natural waterways.

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