North America Native Plant

Maemon Valley Maiden Fern

Botanical name: Thelypteris maemonensis

USDA symbol: THMA13

Life cycle: perennial

Habit: forb

Native status: Native to Pacific Basin excluding Hawaii  

Synonyms: Cyclosorus maemonensis W.H. Wagner & Grether (CYMA28)  âš˜  Sphaerostephanos maemonensis (W.H. Wagner & Grether) Holttum (SPMA14)   

Discovering the Maemon Valley Maiden Fern: A Pacific Island Native If you’ve ever wondered about the unique fern species that call the Pacific islands home, let me introduce you to the Maemon Valley maiden fern (Thelypteris maemonensis). This perennial fern is a fascinating example of the specialized plant life that ...

Discovering the Maemon Valley Maiden Fern: A Pacific Island Native

If you’ve ever wondered about the unique fern species that call the Pacific islands home, let me introduce you to the Maemon Valley maiden fern (Thelypteris maemonensis). This perennial fern is a fascinating example of the specialized plant life that has evolved in some of the world’s most remote island locations.

What is the Maemon Valley Maiden Fern?

The Maemon Valley maiden fern belongs to the Thelypteris genus, a group of ferns known for their delicate fronds and adaptability to various growing conditions. As a forb-type plant, this fern lacks significant woody tissue and maintains its growing points at or below ground level, allowing it to persist year after year in its native habitat.

You might also encounter this species referenced by its scientific synonyms, including Cyclosorus maemonensis or Sphaerostephanos maemonensis, depending on the botanical classification system being used.

Where Does It Naturally Grow?

This maiden fern is native to the Pacific Basin, specifically found in Guam and Palau. These island locations represent some of the most biodiverse and ecologically unique environments in the Pacific, where many plant species have evolved in isolation to develop distinct characteristics.

Is It Beneficial to Have in a Garden?

For gardeners in Guam and Palau, the Maemon Valley maiden fern represents an important piece of their natural heritage. Native ferns like this one typically offer several benefits:

  • They’re naturally adapted to local climate conditions
  • They support local ecosystem balance
  • They require less water and maintenance than non-native alternatives
  • They help preserve regional botanical diversity

However, detailed information about this specific fern’s horticultural requirements and garden performance is limited, which suggests it may be quite specialized in its natural habitat requirements.

How to Identify the Maemon Valley Maiden Fern

As a member of the Thelypteris family, this fern likely shares some common characteristics with its relatives, though specific identification features for this species aren’t well-documented in general horticultural literature. If you’re in Guam or Palau and suspect you’ve found this native fern, consulting with local botanical experts or native plant societies would be your best bet for positive identification.

Conservation Considerations

Given its limited geographic range on just two Pacific island locations, the Maemon Valley maiden fern represents the type of specialized native species that can be vulnerable to habitat changes. If you’re fortunate enough to encounter this fern in its natural habitat, it’s worth appreciating it as part of the unique botanical heritage of the Pacific islands.

For gardeners interested in native ferns, working with local native plant societies or botanical gardens in Guam and Palau would be the best way to learn more about this species and other native alternatives that might be more readily available for cultivation.

Maemon Valley Maiden Fern

Classification

Group

Fern

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision
Division

Pteridophyta - Ferns

Subdivision
Class

Filicopsida

Subclass
Order

Polypodiales

Family

Thelypteridaceae Ching ex Pic. Serm. - Marsh Fern family

Genus

Thelypteris Schmidel - maiden fern

Species

Thelypteris maemonensis (W.H. Wagner & Grether) B.C. Stone - Maemon Valley maiden fern

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