North America Native Plant

Rusty Swordfern

Botanical name: Polystichum echinatum

USDA symbol: POEC

Life cycle: perennial

Habit: forb

Native status: Native to Puerto Rico  

Synonyms: Polystichum triangulum auct. non (L.) Fée (POTR9)   

Meet the Rusty Swordfern: A Rare Caribbean Native Worth Knowing If you’re fascinated by unique ferns and have a soft spot for rare native plants, let me introduce you to the rusty swordfern (Polystichum echinatum). This intriguing fern species calls the tropical paradise of Puerto Rico home, making it a ...

Meet the Rusty Swordfern: A Rare Caribbean Native Worth Knowing

If you’re fascinated by unique ferns and have a soft spot for rare native plants, let me introduce you to the rusty swordfern (Polystichum echinatum). This intriguing fern species calls the tropical paradise of Puerto Rico home, making it a true Caribbean native that’s as mysterious as it is beautiful.

What Exactly Is the Rusty Swordfern?

The rusty swordfern belongs to the Polystichum genus, a group known for their distinctive sword-like fronds and robust nature. Despite some confusion in plant databases that might classify it incorrectly, this is indeed a true fern – a perennial plant that reproduces via spores rather than seeds and lacks the woody tissue found in shrubs and trees.

As a member of the swordfern family, Polystichum echinatum likely shares the characteristic tough, leathery fronds that make its relatives so distinctive. The rusty part of its common name hints at the warm, earthy tones you might expect to see in its coloring or spore structures.

Where Does It Call Home?

This fern is native exclusively to Puerto Rico, making it a true island endemic. Its natural range appears to be quite limited, restricted to this single Caribbean island territory.

Is This Fern Right for Your Garden?

Here’s where things get a bit tricky. The rusty swordfern is something of a botanical mystery – there’s limited information available about its specific growing requirements, appearance details, or cultivation needs. This lack of readily available information suggests it’s either quite rare in cultivation or perhaps challenging to grow outside its native habitat.

Given its Puerto Rican origins, this fern would likely prefer:

  • Warm, tropical to subtropical conditions
  • High humidity levels
  • Protection from direct, harsh sunlight
  • Consistent moisture without waterlogging

The Conservation Angle

When a native plant has limited distribution and scarce cultivation information, it often indicates rarity or conservation concerns. If you’re lucky enough to encounter this fern, it’s worth appreciating from a conservation perspective. Any rare native plant plays an important role in its ecosystem, potentially supporting specialized wildlife or filling unique ecological niches.

Alternatives for Fern Enthusiasts

If you’re drawn to the idea of growing swordferns but can’t locate the rusty swordfern, consider these more readily available alternatives:

  • Christmas fern (Polystichum acrostichoides) – hardy and widely available
  • Western swordfern (Polystichum munitum) – dramatic and architectural
  • Soft shield fern (Polystichum setiferum) – elegant with finely divided fronds

The Bottom Line

The rusty swordfern represents one of those fascinating botanical puzzles – a native species that reminds us how much we still don’t know about the plant world. While it might not be the easiest fern to add to your garden, knowing about its existence adds to our appreciation for the incredible diversity of native plants, especially those found in unique island ecosystems like Puerto Rico.

If conservation and rare plants intrigue you, keep an eye out for botanical gardens or specialized nurseries that work with Caribbean native plants. They might just have insights into this elusive fern that could satisfy your curiosity – or better yet, help with conservation efforts for this interesting species.

Rusty Swordfern

Classification

Group

Fern

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision
Division

Pteridophyta - Ferns

Subdivision
Class

Filicopsida

Subclass
Order

Polypodiales

Family

Dryopteridaceae Herter - Wood Fern family

Genus

Polystichum Roth - hollyfern

Species

Polystichum echinatum (J.F. Gmel.) C. Chr. - rusty swordfern

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