North America Native Plant

Mountain Phyllostegia

Botanical name: Phyllostegia ambigua

USDA symbol: PHAM9

Life cycle: perennial

Habit: vine

Native status: Native to Hawaii  

Synonyms: Phyllostegia alba H. St. John (PHAL19)  âš˜  Phyllostegia brevidens A. Gray var. ambigua (PHBRA)  âš˜  Phyllostegia brevidens A. Gray var. degeneri Sherff (PHBRD)  âš˜  Phyllostegia brevidens A. Gray var. expansa Sherff (PHBRE)  âš˜  Phyllostegia brevidens A. Gray var. heterodoxa Sherff (PHBRH)  âš˜  Phyllostegia brevidens A. Gray var. hirsutula (Hillebr.) Sherff (PHBRH2)  âš˜  Phyllostegia brevidens A. Gray var. pauciflora Sherff (PHBRP)  âš˜  Phyllostegia brevidens A. Gray var. pubescens Sherff (PHBRP2)  âš˜  Phyllostegia chartacea H. St. John (PHCH8)  âš˜  Phyllostegia degeneri Sherff (PHDE12)  âš˜  Phyllostegia elliptica H. St. John (PHEL7)  âš˜  Phyllostegia haiti H. St. John (PHHA14)  âš˜  Phyllostegia konaensis H. St. John (PHKO2)  âš˜  Phyllostegia longimontis H. St. John (PHLO6)   

Mountain Phyllostegia: A Rare Hawaiian Native Worth Protecting in Your Garden If you’re passionate about native Hawaiian plants and have the right growing conditions, mountain phyllostegia (Phyllostegia ambigua) might just be the perfect addition to your garden. This charming member of the mint family brings authentic island character to landscapes ...

Rare plant alert!

Region: Conservation status by state

Status: S3?: Status is uncertain but is somewhere between the following rankings: Inexact rank: ⚘ Vulnerable: Either very rare and local throughout its range, found only in a restricted range (even if abundant at some locations), or factors are making it vulnerable to extinction. Typically 21 to 100 occurrences or between 3,000 and 10,000 individuals ⚘

Mountain Phyllostegia: A Rare Hawaiian Native Worth Protecting in Your Garden

If you’re passionate about native Hawaiian plants and have the right growing conditions, mountain phyllostegia (Phyllostegia ambigua) might just be the perfect addition to your garden. This charming member of the mint family brings authentic island character to landscapes while supporting Hawaii’s unique ecosystem.

What Makes Mountain Phyllostegia Special

Mountain phyllostegia is a perennial shrub that’s completely native to Hawaii – you won’t find this beauty growing wild anywhere else in the world! As part of the mint family, it shares that characteristic square stem and aromatic foliage that makes these plants so distinctive. This multi-stemmed woody shrub typically grows less than 13-16 feet tall, though it’s usually much more modest in garden settings.

The plant produces small, tubular flowers that range from white to pale pink, creating a delicate display that perfectly complements Hawaii’s native plant palette. Its aromatic leaves add another sensory dimension to your garden, releasing pleasant scents when brushed against or crushed.

Where Mountain Phyllostegia Calls Home

This endemic Hawaiian species grows naturally throughout the Hawaiian Islands, where it has evolved specifically to thrive in the archipelago’s unique climate and conditions.

Important Conservation Note

Here’s something every responsible gardener should know: mountain phyllostegia has a conservation status that suggests it may be of concern. While the exact status is still being defined, this means you should only obtain plants from reputable, responsible sources. Never collect from the wild, and consider yourself a steward of this special species if you choose to grow it.

Growing Mountain Phyllostegia Successfully

If you live in USDA hardiness zones 10-12, you’re in luck – mountain phyllostegia could thrive in your garden! Here’s what this Hawaiian native needs to flourish:

Ideal Growing Conditions

  • Partial shade to filtered sunlight (mimicking its natural understory habitat)
  • Well-draining soil that doesn’t stay waterlogged
  • Consistent moderate moisture – not too wet, not too dry
  • Protection from strong winds

Planting and Care Tips

  • Choose a spot with morning sun and afternoon shade
  • Improve soil drainage by adding organic matter or planting on a slight slope
  • Apply organic mulch around the base to retain moisture and suppress weeds
  • Water regularly during dry periods, but allow soil to dry slightly between waterings
  • Prune lightly after flowering to maintain shape

Perfect for Native Hawaiian Landscapes

Mountain phyllostegia shines in native Hawaiian garden designs, where it works beautifully as an understory shrub. It’s perfect for creating that authentic island feel in woodland gardens or naturalized areas. Consider pairing it with other native Hawaiian plants like native ferns, ohia trees, or other indigenous shrubs for a landscape that truly celebrates Hawaii’s natural heritage.

Supporting Local Wildlife

By growing mountain phyllostegia, you’re not just adding beauty to your landscape – you’re providing valuable habitat and food sources for Hawaii’s native insects and other wildlife. Native plants like this one have co-evolved with local creatures, creating relationships that introduced plants simply can’t replicate.

The Bottom Line

Mountain phyllostegia is a wonderful choice for gardeners in tropical and subtropical climates who want to support native Hawaiian biodiversity. Just remember to source your plants responsibly and treat them as the conservation treasures they are. With the right growing conditions and a little care, you’ll have a piece of authentic Hawaii thriving in your own backyard!

Whether you’re creating a native Hawaiian garden or simply want to add something truly special to your landscape, mountain phyllostegia offers unique beauty with important ecological benefits. It’s these kinds of plants that remind us why choosing natives isn’t just good gardening – it’s environmental stewardship at its finest.

Mountain Phyllostegia

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

Lamiales

Family

Lamiaceae Martinov - Mint family

Genus

Phyllostegia Benth. - phyllostegia

Species

Phyllostegia ambigua (A. Gray) Hillebr. - mountain phyllostegia

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