North America Native Plant

Honolulu Cyanea

Botanical name: Cyanea acuminata

USDA symbol: CYAC5

Life cycle: perennial

Habit: subshrub

Native status: Native to Hawaii  

Synonyms: Cyanea acuminata (Gaudich.) Hillebr. var. calycina Hosaka (CYACC)  âš˜  Cyanea occultans H. St. John (CYOC4)   

Honolulu Cyanea: A Rare Hawaiian Treasure Worth Protecting If you’ve ever dreamed of growing a piece of authentic Hawaiian paradise in your garden, the Honolulu cyanea might just capture your heart. But before you start planning where to plant this stunning native shrub, there’s something important you need to know ...

Rare plant alert!

Region: United States

Status: S2: Status is uncertain but is somewhere between the following rankings: Imperiled: Extremely rare due to factor(s) making it especially vulnerable to extinction. Typically 6 to 20 occurrences or few remaining individuals (1,000 to 3,000) ⚘ Endangered: In danger of extinction throughout all or a significant portion of its range. ⚘

Region: United States

Honolulu Cyanea: A Rare Hawaiian Treasure Worth Protecting

If you’ve ever dreamed of growing a piece of authentic Hawaiian paradise in your garden, the Honolulu cyanea might just capture your heart. But before you start planning where to plant this stunning native shrub, there’s something important you need to know about its conservation status.

What Makes Honolulu Cyanea Special?

Known botanically as Cyanea acuminata, the Honolulu cyanea is a perennial shrub that’s as beautiful as it is rare. This member of the bellflower family typically grows as a multi-stemmed woody plant, usually reaching heights of 13 to 16 feet, though it can sometimes grow taller or develop a single stem depending on environmental conditions.

What sets this plant apart is its distinctive tropical appearance, with large leaves and striking flowers that have evolved specifically for Hawaii’s unique ecosystem. It’s a true endemic species, meaning it exists nowhere else on Earth except in the Hawaiian islands.

Where Does It Naturally Grow?

Honolulu cyanea is exclusively native to Hawaii, where it grows in the state’s mesic to wet forest environments. This shrub has adapted to the islands’ unique climate and growing conditions over thousands of years.

A Critical Conservation Concern

Here’s what every gardener needs to know: Honolulu cyanea is critically rare. It holds a Global Conservation Status of S2, meaning it’s imperiled due to extreme rarity, with typically only 6 to 20 occurrences and fewer than 1,000 to 3,000 remaining individuals. In the United States, it’s officially listed as Endangered.

This means that while you absolutely can grow this remarkable plant, you should only do so with material that has been responsibly and legally sourced. Never collect from wild populations, and always purchase from reputable nurseries that specialize in Hawaiian native plants and conservation.

Growing Honolulu Cyanea: What You Need to Know

If you’re fortunate enough to obtain responsibly sourced Honolulu cyanea, here’s how to give it the best care:

Climate Requirements

  • USDA Hardiness Zones 10-11 only (tropical and subtropical climates)
  • Requires high humidity and consistent moisture
  • Prefers filtered light rather than full sun

Soil and Water Needs

  • Well-draining but moisture-retentive soil
  • Consistent watering – this isn’t a drought-tolerant plant
  • Benefits from organic mulch to maintain soil moisture

Garden Placement

Honolulu cyanea has a wetland status of Facultative Upland, meaning it usually grows in non-wetland areas but can tolerate some wetland conditions. This makes it quite versatile for different garden situations, as long as its moisture needs are met.

Why Grow Honolulu Cyanea?

Beyond its stunning tropical beauty, growing Honolulu cyanea serves a greater purpose. By cultivating this endangered species in appropriate gardens, you’re:

  • Supporting conservation efforts for Hawaiian native plants
  • Creating habitat that can support native Hawaiian wildlife
  • Preserving genetic diversity outside of wild populations
  • Adding an authentic piece of Hawaiian natural heritage to your landscape

Is This Plant Right for Your Garden?

Honolulu cyanea is perfect for you if you:

  • Live in USDA zones 10-11
  • Have space for a medium to large shrub
  • Can provide consistent moisture and humidity
  • Want to support native plant conservation
  • Appreciate rare and unique tropical plants

However, this plant isn’t suitable if you’re looking for something low-maintenance or drought-tolerant. It requires dedicated care and the right climate conditions to thrive.

The Bottom Line

Honolulu cyanea is more than just a beautiful garden plant—it’s a living piece of Hawaiian natural heritage that needs our protection. If you can provide the right growing conditions and source your plant responsibly, you’ll be rewarded with a truly unique addition to your garden while contributing to important conservation efforts.

Remember, with rare plants comes great responsibility. Always buy from reputable sources, never collect from the wild, and consider sharing seeds or cuttings with other conservation-minded gardeners to help ensure this species has a future both in cultivation and in its native Hawaiian forests.

Honolulu Cyanea

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

Campanulales

Family

Campanulaceae Juss. - Bellflower family

Genus

Cyanea Gaudich. - cyanea

Species

Cyanea acuminata (Gaudich.) Hillebr. - Honolulu cyanea

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