Hibiscadelphus hualalaiensis

Main Plant Information

Genus

Hibiscadelphus

Species

hualalaiensis

Hawaiian Names with Diacritics

• Hau kuahiwi

Hawaiian Names

• Hau kuahiwi

Common Names

• Hualālai hau kuahiwi

Did You Know…?

Hibiscadelphus means “brother of Hibiscus,” suggesting their close affiliation to the genus Hibiscus . The curved flowers are perfectly designed to match their pollinators the Hawaiian honeycreepers which have curved beaks.

Plant Characteristics

Distribution Status

Endemic

Endangered Species Status

Federally Listed

Plant Form / Growth Habit

• Shrub
• Tree

Mature Size, Height (in feet)

• Shrub, Tall, Greater than 10
• Tree, Dwarf, Less than 15
• Tree, Small, 15 to 30

Life Span

Long lived (Greater than 5 years)

Landscape Uses

• Accent
• Specimen Plant

Additional Landscape Use Information

Very rare in cultivation.

While Hibiscadelphus distans does well and flowers at lower elevations, H. hualalaiensis appears to be rather challenging and slowly declines over time.* It seems to grow well in garden settings at slightly higher and cooler temperatures around 1000 feet on Hawaiʻi Island.

• These observations are based on a few cultivated specimens from sea level up to around 300 ft. More conclusive data is needed. [David Eickhoff, Native Plants Hawaiʻi]

Plant Produces Flowers

Yes

Flower Characteristics

Flower Type

Not Showy

Flower Colors

• Green
• Purple
• Yellow

Additional Flower Color Information

The curved flowers, which never fully open, have greenish yellow petals (corolla) externally to yellowish green fading to purple within, but often hidden by the large (4-6") leaves.

Additional Blooming Period and Fruiting Information

After flowering, woody capsules containing fuzzy seeds.

Leaf Characteristics

Plant texture

• Medium
• Coarse

Leaf Colors

• Light Green
• Medium Green

Pests and Diseases

Additional Pest & Disease Information

Whiteflies can congregate under the leaves and aphids in the new growth or bud areas.* These pests can be washed off or a horticultural oil or systemic insecticide can be applied.

Red spider mites will occasionally attack plants from underside of the leaves and be controlled by washing off with water, but a miticide is often more effective.

Chinese rose beetles will chew unslightly holes in leaves giving them a lacey appearance. In severe cases this can eventually weaken or stress the plant.

Black twig borers are a serious problem that should be treated immediately . Look for twigs will look dead. If noticed early, cut off twig below the infected area, secure in a plastic bag and dispose of in rubbish container. Do not use in compose pile. If damge is extensive treat with a systemic insecticide. [David Eickhoff, Native Plants Hawaiʻi]

• Hibiscadelphus distans has similar type leaves to the featured species and therefore the pest & disease information above may perhaps be useful for H. hualalaiensis as well.

Growth Requirements

Water Requirements

• Dry

Soil must be well drained

Yes

Light Conditions

• Full sun
• Partial sun

Additional Lighting Information

Full sun is best.

Tolerances

• Drought

Soils

• Cinder

Limitations

Special Growing Needs

This species does not appear to difficult to cultivate, but as noted earlier, plants seem to prefer the cooler higher elevations than the hot urban lowland areas.

Environmental Information

Natural Range

• Hawaiʻi

Natural Zones (Elevation in feet, Rainfall in inches)

No data available.

Additional Habitat Information

Very rare in dry to mesic forest, lava flows. Formerly from Hualālai and Waihou, North Kona, Hawaiʻi Island.

Special Features and Information

General Information

Hibiscadelphus is an endemic genus of seven endangered or extinct species in the Mallow family or Malvaceae, with four species still existing. Additionally, an eighth species " Hibiscadelphus sp. nov. Maui" has been recently discovered.

Also, an unnatural hybrid known as Hibiscadelphus x puakuahiwi ( Hibiscadelphus giffardianus x H. hualalaiensis ) were once common in Kīpukakī, Hawaiʻi Island. But since these two species did not naturally exist together and threatened the genetic integrity of Hibiscadelphus giffardianus , the hybrids and the planted out H. hualalaiensis have been destroyed since their discovery in 1973. Apparently at least one of these hybrids, as of 2011, one plant still exists. However, presumumably hybrids exist elsewhere in cultivation.

This is a complex genus and is considered to be one of the rarest groups of trees in the world. [3]

Etymology

The generic name Hibiscadelphus is from the Greek hibiscum , marsh mallow, and delphi , brother, meaning “brother of Hibiscus,” suggesting their close affiliation to the genus Hibiscus .

The specific epithet hualalaiensis is named for Hualālai on Hawaiʻi, a location where it was once found.

Hawaiian Name:

Hau kuahiwi literally means " hau of the mountains," referring to it’s resemblance to hau and mountain habitat. Hau ( Hibiscus tiliaceus ) is a Polynesian introduced plant from in the lowlands.

Background Information

The flowers are abundant in nectar for pollinating birds such as honeyeaters (Meliphagidae) and honeycreepers (Drepipandidae). It is possible that the decline and extinction of certain native birds, especially honeyeaters such as ʻōʻō ( Moho spp.) and kioea ( Chaetoptila ), may be closely linked to the decline of Hibiscadelphus . [1,2]

As of 1977, 2 or 3 plants still existed in its natural habitat. The last Hualālai hau kuahiwi ( Hibiscadelphus hualalaiensis ) in the wild, however, died in 1992. Fortunately this species survives in cultivation and has been planted within exclosures in forest reserves on Hawaiʻi Island.

Saving a RareHibiscadelphusFrom Extinction:

A very rare relative the Kīlauea hau kuahiwi ( Hibiscadelphus giffardianus ) was featured in a 2002 article entitled A Tree’s Tribulation by Jenell Talley. It relates how a plant teetering on survival can be saved from total extinction by the efforts of a few conscientious people:

“Hibiscadelphus giffardianus, also called hau kuahiwi, is endemic to Hawaii Volcanoes National Park. The species was first described in 1911 by Austrian botanist Joseph Rock. Before the original tree died in 1930, cuttings were collected and at least one tree was propagated on land adjacent to what is now Hawaii Volcanoes. This tree died in 1940, but one cutting remained, keeping the species alive. The plant survived in cultivation and was replanted in the park in the 1950s. The species has been reduced to a single tree at least three times. Each tree is derived from the 1911 original.”

She continues: “Steps are being taken to increase the tree population, although currently Belfield, Linda Pratt, a botanist working for the U.S. Geological Survey Pacific Islands Ecosystems Research Center, and Tim Tunison, chief of resources management at Hawaii Volcanoes, are the only scientists dedicated to the recovery effort. The tree has no specific recovery program, but Belfield is working on the park’s Rare Plants Stabilization Project, which began last year. The project focuses on examining the status of rare and endangered plant species, including the H. giffardianus, in four ecological zones in the park. Seeds, fruit, and cuttings are collected and raised in the park’s greenhouse, then planted in the park. More than 200 trees have been planted in the last few years as part of an experiment conducted by U.S. Geological Survey researchers to study damage caused by rats. Despite these efforts, more work remains before the trees can make it off the endangered list. “It is unrealistic to imagine that this species will ever be delisted unless it goes extinct,” Pratt says, adding, that reintroducing the species to its natural habitat and having it be self-sustaining is the park’s goal.” [4]

Early Hawaiian Use

No use for hau kuahiwi is yet known.

Modern Use

Not known to be in general use for landscapes.

Additional References

[1] “Recovery Plan for Hibiscadelphus distans,” by USFWS, page 5.

[2] “The Hawaiian Honeycreeper: Drapandidae” by H. Douglas Pratt, page 143.

[3] “The Plant Genus Hibiscadelphus in Hawaiʻi” by James K. Baker, pages 20, 21.

[4] National Parks Conservation Association July-August 2002 issue http://www.npca.org/home.html [Accessed on 1/13/13]