North America Native Plant

Kahili Phyllostegia

Botanical name: Phyllostegia kahiliensis

USDA symbol: PHKA8

Life cycle: perennial

Habit: forb

Native status: Native to Hawaii  

Kahili Phyllostegia: A Rare Hawaiian Treasure Worth Protecting Meet one of Hawaii’s most precious botanical gems – the Kahili phyllostegia (Phyllostegia kahiliensis). This delicate native perennial might not be the showiest plant in your garden, but what it lacks in drama, it more than makes up for in conservation value ...

Rare plant alert!

Region: Conservation status by state

Status: S1?: Status is uncertain but is somewhere between the following rankings: Inexact rank: ⚘ 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) ⚘

Kahili Phyllostegia: A Rare Hawaiian Treasure Worth Protecting

Meet one of Hawaii’s most precious botanical gems – the Kahili phyllostegia (Phyllostegia kahiliensis). This delicate native perennial might not be the showiest plant in your garden, but what it lacks in drama, it more than makes up for in conservation value and quiet charm.

What Makes Kahili Phyllostegia Special?

This lovely little forb belongs to the mint family, and like its aromatic cousins, it produces fragrant foliage and delicate tubular flowers. The Kahili phyllostegia creates small spikes of white to pale lavender blooms that have a subtle beauty perfect for those who appreciate understated elegance in their gardens.

As a herbaceous perennial, this plant lacks woody stems but returns year after year, forming a low-growing presence in the garden. Its soft, textured leaves and compact growth habit make it an excellent choice for filling in gaps in native plantings or creating gentle ground cover in shaded areas.

Where Does It Come From?

The Kahili phyllostegia is endemic to Hawaii, meaning you won’t find it growing wild anywhere else on Earth. Specifically, this rare beauty calls the islands of Kauai and Oahu home, where it originally thrived in the understory of native forests.

Important Conservation Alert

Here’s where we need to have a serious conversation. The Kahili phyllostegia carries a Global Conservation Status of S1?, which translates to Critically Imperiled. This means there are typically five or fewer known populations in the wild, with very few remaining individuals – we’re talking fewer than 1,000 plants total.

If you’re considering adding this plant to your garden, that’s wonderful! But please, please make sure you’re sourcing it responsibly. Only purchase from reputable native plant nurseries that propagate from legally obtained, ethically sourced material. Never collect from the wild – every plant in nature is precious for the species’ survival.

Garden Role and Design Ideas

When grown in appropriate conditions, Kahili phyllostegia serves several valuable roles in the landscape:

  • Understory planting in native Hawaiian garden designs
  • Ground cover for shaded areas
  • Conservation garden centerpiece
  • Educational plant for demonstrating Hawaiian biodiversity

This plant is perfectly suited for native Hawaiian gardens, conservation-focused landscapes, and shade gardens where its subtle beauty can be appreciated up close.

Growing Conditions and Care

If you’re fortunate enough to obtain responsibly sourced Kahili phyllostegia, here’s how to help it thrive:

Light Requirements: This forest understory native prefers partial to full shade. Direct sunlight can stress the plant, so think filtered light or morning sun with afternoon shade.

Soil Needs: Well-draining soil that stays consistently moist (but not waterlogged) works best. The plant has a facultative wetland status, meaning it can handle both moist and moderately dry conditions, but consistent moisture is preferred.

Climate Considerations: Being a tropical Hawaiian native, this plant thrives in USDA hardiness zones 10-12. If you live outside these zones, you’ll need to grow it as a greenhouse or indoor plant.

Planting and Care Tips

  • Plant in spring when temperatures are consistently warm
  • Mulch around the base to retain moisture and suppress weeds
  • Water regularly but ensure good drainage to prevent root rot
  • Avoid heavy fertilization – native plants typically prefer lean conditions
  • Protect from strong winds which can damage the delicate foliage

Wildlife and Pollinator Benefits

While specific wildlife benefits aren’t well-documented, as a member of the mint family producing tubular flowers, Kahili phyllostegia likely attracts native Hawaiian insects and potentially small birds. Every native plant plays a role in supporting the complex web of Hawaiian ecosystems, even if we don’t fully understand all the connections yet.

The Bottom Line

Should you plant Kahili phyllostegia? If you can source it responsibly and provide the right growing conditions, absolutely! You’ll be participating in conservation efforts while enjoying a truly unique piece of Hawaiian natural heritage. Just remember – with great botanical beauty comes great responsibility. This rare gem deserves our utmost care and respect.

By choosing to grow critically imperiled native plants like Kahili phyllostegia, you’re not just gardening – you’re actively participating in conservation. And that’s pretty amazing, don’t you think?

Kahili 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 kahiliensis H. St. John - Kahili phyllostegia

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