North America Native Plant

Two-edged Bristle Fern

Botanical name: Trichomanes bimarginatum

USDA symbol: TRBI9

Life cycle: perennial

Habit: forb

Native status: Native to Pacific Basin excluding Hawaii  

Synonyms: Didymoglossum bimarginatum (Bosch) Ebihara & K. Iwats. (DIBI9)   

Two-Edged Bristle Fern: A Rare Pacific Treasure Meet the two-edged bristle fern (Trichomanes bimarginatum), one of nature’s most delicate and elusive creations. This tiny tropical fern might not be headed to your backyard garden anytime soon, but it’s worth knowing about this fascinating Pacific island native that showcases just how ...

Two-Edged Bristle Fern: A Rare Pacific Treasure

Meet the two-edged bristle fern (Trichomanes bimarginatum), one of nature’s most delicate and elusive creations. This tiny tropical fern might not be headed to your backyard garden anytime soon, but it’s worth knowing about this fascinating Pacific island native that showcases just how diverse and specialized the fern world can be.

What Exactly Is the Two-Edged Bristle Fern?

The two-edged bristle fern belongs to the filmy fern family, and filmy really says it all. These aren’t your typical robust garden ferns. Instead, think tissue-paper thin fronds that are almost translucent, creating an ethereal, almost ghostly appearance. As a perennial species, this little fern has adapted to thrive in very specific tropical conditions that most of us can only dream of replicating.

You might also see this fern listed under its scientific synonym Didymoglossum bimarginatum in some references, but Trichomanes bimarginatum is the currently accepted name.

Where Does This Fern Call Home?

This rare beauty is native to the Pacific Basin, specifically documented in Guam and Palau. It’s part of that incredible biodiversity found on tropical Pacific islands, where unique microclimates have allowed specialized plants like this to evolve in isolation.

Can You Grow It in Your Garden?

Here’s where things get interesting (and a bit challenging). The two-edged bristle fern is definitely not your average garden center find. This specialized tropical species requires very specific conditions that are nearly impossible to replicate outside of its native habitat or a carefully controlled greenhouse environment.

If you’re determined to try growing this fern, you’ll need:

  • Extremely high humidity (think rainforest levels)
  • Filtered, indirect light
  • Consistent moisture without waterlogging
  • Warm temperatures year-round
  • A terrarium or specialized greenhouse setup

Is It Worth the Effort?

Unless you’re a serious fern collector with a proper setup, this probably isn’t the plant for you. The two-edged bristle fern is more of a look but don’t touch species that’s best appreciated in its natural habitat or specialized botanical collections.

For most gardeners interested in ferns, there are plenty of easier-to-grow native alternatives depending on your location. If you’re in a temperate climate, consider native species like Christmas fern or royal fern. If you’re in a subtropical area, there are still more forgiving native ferns that will give you that tropical look without the headaches.

The Bottom Line

The two-edged bristle fern is one of those plants that reminds us just how incredible and specialized nature can be. While it might not be destined for your garden, knowing about species like this helps us appreciate the amazing diversity of plant life on our planet. Sometimes the most beautiful plants are the ones we admire from afar, knowing they’re perfectly adapted to their own special corner of the world.

If you ever find yourself in Guam or Palau, keep an eye out for this delicate beauty in its natural habitat – just remember to look with your eyes, not your hands!

Two-edged Bristle Fern

Classification

Group

Fern

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision
Division

Pteridophyta - Ferns

Subdivision
Class

Filicopsida

Subclass
Order

Polypodiales

Family

Hymenophyllaceae Mart. - Filmy Fern family

Genus

Trichomanes L. - bristle fern

Species

Trichomanes bimarginatum (Bosch) Bosch - two-edged bristle fern

Plant data source: USDA, NRCS 2025. The PLANTS Database. https://plants.usda.gov,. 2/25/2025. National Plant Data Team, Greensboro, NC USA