North America Native Plant

Ridged Pteralyxia

Botanical name: Pteralyxia macrocarpa

USDA symbol: PTMA

Life cycle: perennial

Habit: tree

Native status: Native to Hawaii  

Synonyms: Pteralyxia caumiana O. Deg. (PTCA2)   

Ridged Pteralyxia: A Rare Hawaiian Native Worth Protecting Meet the ridged pteralyxia (Pteralyxia macrocarpa), one of Hawaii’s most endangered native trees that deserves our attention and protection. This remarkable species tells a story of island evolution and conservation challenges that every native plant enthusiast should know about. What Makes Ridged ...

Rare plant alert!

Region: United States

Status: S1: Status is uncertain but is somewhere between the following rankings: Critically Imperiled: Extremely rare due to factor(s) making it especially vulnerable to extinction. Typically 5 or fewer occurrences or very few remaining individuals (<1,000) ⚘ Endangered: In danger of extinction throughout all or a significant portion of its range. ⚘

Region: United States

Ridged Pteralyxia: A Rare Hawaiian Native Worth Protecting

Meet the ridged pteralyxia (Pteralyxia macrocarpa), one of Hawaii’s most endangered native trees that deserves our attention and protection. This remarkable species tells a story of island evolution and conservation challenges that every native plant enthusiast should know about.

What Makes Ridged Pteralyxia Special

The ridged pteralyxia is a perennial tree that typically grows as a single-stemmed woody plant, reaching heights of 13-16 feet or more under ideal conditions. In some environments, it may develop a shorter, multi-stemmed growth form. This native Hawaiian species showcases the unique botanical heritage of the islands with its glossy, leathery leaves and delicate white flowers that add subtle beauty to the landscape.

Where to Find This Rare Beauty

Ridged pteralyxia is endemic to Hawaii, meaning it exists nowhere else on Earth. Historically, this species could be found on the islands of Oahu and Molokai, where it grew in specialized habitats that supported its unique needs.

A Critical Conservation Story

Important Conservation Alert: Before considering this plant for your garden, you need to know that ridged pteralyxia has a Global Conservation Status of S1, meaning it’s critically imperiled. In the United States, it’s officially listed as Endangered, with typically five or fewer occurrences and very few remaining individuals (fewer than 1,000) in the wild.

This rarity status means that if you’re interested in growing this species, you should only obtain plants through responsible sources such as:

  • Authorized botanical gardens with conservation programs
  • Native plant societies with proper permits
  • Conservation nurseries working on species recovery
  • Educational institutions involved in Hawaiian plant preservation

Garden Role and Landscape Use

Due to its endangered status, ridged pteralyxia is best suited for:

  • Conservation gardens focused on Hawaiian native species
  • Botanical collections supporting species preservation
  • Educational landscapes that showcase rare Hawaiian plants
  • Specialized native Hawaiian plant gardens

This isn’t a plant for casual landscaping – it’s a living piece of Hawaiian natural heritage that requires dedicated care and conservation-minded gardening.

Growing Conditions and Care

Ridged pteralyxia thrives in tropical conditions and is suitable for USDA hardiness zones 10-11. If you’re fortunate enough to obtain this species through proper conservation channels, here’s what it needs:

  • Climate: Warm, humid tropical conditions year-round
  • Sunlight: Partial shade to full sun
  • Soil: Well-draining soil that doesn’t stay waterlogged
  • Water: Consistent moisture without overwatering
  • Temperature: Consistently warm temperatures (tropical zones only)

Supporting Pollinators and Wildlife

The small white flowers of ridged pteralyxia likely provide nectar and pollen for native Hawaiian insects, contributing to the complex web of island ecology. By supporting this species, you’re helping maintain important relationships between native plants and native pollinators.

The Bottom Line for Gardeners

Ridged pteralyxia represents both an incredible opportunity and a serious responsibility. This endangered Hawaiian endemic isn’t suitable for most home gardens, but it plays a crucial role in conservation efforts. If you’re passionate about Hawaiian native plants and have the proper growing conditions (tropical zones 10-11), consider supporting conservation organizations that work to protect and propagate this species.

For most gardeners outside Hawaii or without access to conservation programs, the best way to support ridged pteralyxia is by learning about Hawaiian plant conservation and supporting organizations working to protect endangered island species. Every rare plant saved contributes to preserving the unique natural heritage of Hawaii for future generations.

Remember: with great rarity comes great responsibility. This isn’t just gardening – it’s conservation in action.

Ridged Pteralyxia

Classification

Group

Dicot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Magnoliopsida - Dicotyledons

Subclass

Asteridae

Order

Gentianales

Family

Apocynaceae Juss. - Dogbane family

Genus

Pteralyxia K. Schum. - pteralyxia

Species

Pteralyxia macrocarpa (Hillebr.) K. Schum. - ridged pteralyxia

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