North America Native Plant

White Rosemallow

Botanical name: Hibiscus arnottianus immaculatus

USDA symbol: HIARI

Life cycle: perennial

Habit: shrub

Native status: Native to Hawaii  

Synonyms: Hibiscus immaculatus Roe (HIIM)   

White Rosemallow: Hawaii’s Endangered Beauty Worth Protecting Meet the white rosemallow (Hibiscus arnottianus immaculatus), one of Hawaii’s most stunning yet critically endangered native flowering shrubs. Known locally as White Koki’o, this remarkable plant produces gorgeous white blooms that seem to glow against Hawaii’s lush green landscapes. But before you start ...

Rare plant alert!

Region: United States

Status: S3T1: Status is uncertain but is somewhere between the following rankings: Subspecies or variety is 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) ⚘ 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 ⚘ Endangered: In danger of extinction throughout all or a significant portion of its range. ⚘

Region: United States

White Rosemallow: Hawaii’s Endangered Beauty Worth Protecting

Meet the white rosemallow (Hibiscus arnottianus immaculatus), one of Hawaii’s most stunning yet critically endangered native flowering shrubs. Known locally as White Koki’o, this remarkable plant produces gorgeous white blooms that seem to glow against Hawaii’s lush green landscapes. But before you start planning where to plant one, there’s something crucial you need to know about this botanical treasure.

A Rare Hawaiian Gem

The white rosemallow isn’t just any pretty flower – it’s an endangered species that deserves our utmost respect and care. With a conservation status that puts it at serious risk, this native Hawaiian shrub has become increasingly rare in the wild. If you’re considering adding one to your garden, it’s absolutely essential that you source it responsibly from reputable native plant nurseries or conservation programs.

Where You’ll Find White Rosemallow

This perennial shrub calls Hawaii home and only Hawaii. You’ll find it naturally occurring across several Hawaiian islands, including Oahu, Molokai, Lanai, and Maui. As a true endemic species, it evolved specifically in these island conditions and exists nowhere else on Earth naturally.

What Makes It Special

Picture this: a multi-stemmed woody shrub that can reach up to 13-16 feet tall, adorned with spectacular white flowers that measure 4-6 inches across. Each bloom features a striking red center with prominent stamens that create a stunning contrast against the pure white petals. The plant blooms throughout the year in ideal conditions, making it a continuous source of beauty in the landscape.

Also known by its synonym Hibiscus immaculatus Roe, this shrub has the typical growth habit of its hibiscus family – multiple stems arising from near the ground, creating a full, bushy appearance.

Perfect for Special Gardens

If you’re lucky enough to obtain a white rosemallow through proper conservation channels, it shines best in:

  • Native Hawaiian heritage gardens
  • Tropical landscape designs with cultural significance
  • Conservation gardens focused on endangered species
  • Specimen plantings where its unique beauty can be showcased

Growing Conditions (USDA Zones 10-12 Only)

Let’s be honest – unless you live in tropical or subtropical conditions (USDA hardiness zones 10-12), this plant isn’t going to work for you. White rosemallow needs:

  • Warm, humid tropical climate year-round
  • Full sun to partial shade exposure
  • Well-draining soil that doesn’t stay soggy
  • Regular watering without waterlogging
  • Protection from strong winds

Care Tips for Success

If you’re in the right climate zone and have responsibly sourced your plant, here’s how to keep it thriving:

  • Water consistently but ensure excellent drainage
  • Provide some wind protection, especially for young plants
  • Prune lightly after flowering periods to maintain shape
  • Mulch around the base to retain moisture and suppress weeds
  • Be patient – this isn’t a fast-growing plant

Supporting Pollinators and Wildlife

White rosemallow plays an important role in Hawaii’s ecosystem. Its large, nectar-rich flowers attract various pollinators, including native Hawaiian species that have co-evolved with this plant. By growing it responsibly, you’re not just adding beauty to your garden – you’re participating in conservation efforts that support Hawaii’s unique biodiversity.

The Bottom Line

Should you plant white rosemallow? Only if you can do so responsibly. This means sourcing from legitimate conservation nurseries, living in an appropriate tropical climate, and understanding that you’re caring for an endangered species that deserves respect and proper stewardship.

If you’re not in Hawaii or similar tropical zones, consider supporting conservation efforts from afar and choose appropriate native plants for your own region instead. Sometimes the best way to appreciate a rare plant is to help protect it in its natural habitat while growing natives that belong in your own backyard.

For those fortunate enough to grow white rosemallow responsibly, you’ll be rewarded with spectacular blooms and the satisfaction of participating in important conservation work. Just remember – with great beauty comes great responsibility.

White Rosemallow

Classification

Group

Dicot

Kingdom

Plantae - Plants

Subkingdom

Tracheobionta - Vascular plants

Superdivision

Spermatophyta - Seed plants

Division

Magnoliophyta - Flowering plants

Subdivision
Class

Magnoliopsida - Dicotyledons

Subclass

Dilleniidae

Order

Malvales

Family

Malvaceae Juss. - Mallow family

Genus

Hibiscus L. - rosemallow

Species

Hibiscus arnottianus A. Gray - white rosemallow

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