Metrosideros polymorpha
Myrtaceae or Myrtle family
Synonyms: Metrosideros collina, Nania glabrifolia, Nania macropus, Nania polymorpha, Nania pumila
Note: Since there is a great number of synonyms with subspecific names, we chose to use only synonymous names with genus and species.
ʻŌhiʻa
ʻŌhiʻa lehua, Lehua
Natural Range & Environment
A common endemic tree found on Kauaʻi, Oʻahu, Lānaʻi, Molokaʻi, Maui, and Hawaiʻi Island from near sea level to 2,200 m (7,218 ft) on most of the main islands and often a major component of native Hawaiian forests [Wagner et al. 1990].
The specific epithet polymorpha is from the Greek poly, many, and morphos, forms, in reference to the numerous forms or shapes of this species. These are a few of the many flower colors and leaf forms from cultivated trees.
Description
Small erect to prostrate shrubs to tall trees with usually rough bark, sometimes smooth.
Leaf buds, or liko, can be glabrous (smooth) or covered in fuzz or woolly; leaves are usually glabrous or mostly so. Leaves range between 1.5-7.6 cm (.5-3 in) long. Leaves exhibit a wide range of characteristics, including size, color, shape, texture, and the presence or absence of fuzz. Specific names have been assigned to different leaf forms. For example, ʻōhiʻa with very small leaves are commonly referred to as lehua lau liʻi or ʻōhiʻa lau liʻi. Similarly, ʻōhiʻa with sessile (no petiole) and cordate (heart-shaped) leaves are known as lehuakūmakua or ʻōhiʻa kū ma kua.
Flower petals, found at the very base, and the carpel, which includes the stigma and styes, the pronounced filaments that give the flowers their pom-pom-like appearance, are usually the same color. Floral colors can be typically red of various shades, light to dark yellow, orange, and salmon pink.
Seed capsules form after flowering and are brown and woody when ripe. The seeds are tiny and light and dispersed by the wind.
ʻŌhiʻa produces a variety of flower colors, each with its own unique name and significance. The red-flowered ʻōhiʻa is known as ʻōhiʻa ʻulaʻula, while those with dark red flowers are referred to as ʻōhiʻa ʻāpane and lehua ʻāpane, named after the ʻapapane, a red and black feathered honeycreeper. Additionally, ʻōhiʻa with yellow blossoms are called lehua mamo, in honor of the Hawaiʻi mamo (Drepanis pacifica), an extinct honeycreeper known for its prized yellow feathers [Pratt 2005].
Historical accounts from residents mention dark-colored ʻōhiʻa flowers near Keahikawelo, Lānaʻi, that were described as either black or brown but may have actually been a very dark shade of yellow [Munro 2007].
Furthermore, there are bi-colored ʻōhiʻa flowers, such as the yellow/orange variety, possibly referred to as lehua mamo ʻōʻā ʻalani. (Peter VanDyke, Amy Greenwell Ethnobotanical Garden, personal communication)
These unique flower forms add to the diversity and beauty of ʻōhiʻa. Overall, ʻōhiʻa flowers showcase a stunning array of colors, each with its own story and significance in Hawaiian culture.
Some believe in the existence of a pure, snow-white form of the ʻōhiʻa flower [Neal 1965]. While there are at least five species native to New Zealand that boast pure white flowers, it is possible that some have mistaken these for ʻōhiʻa flowers that have been planted in Hawaiʻi. There are other plants that could be mistaken too that look similar to an untrained eye (e.g., Calliandra spp.) The February 1998 issue of Hawaii Horticulture notes that "There are stories of native white ohia but one has never been seen in recent times and they are extremely rare, if they exist at all." However, Hawaiian names such as ʻōhiʻa hākea or lehua haʻakea (cream), ʻōhiʻa kea or lehua kea (clear white), and ʻōhiʻa lehua puakea or lehua pua kea (pale) suggest a wide range of whitish-flower forms. Additionally, pale or light yellow (hālena) flower forms are also known to exist.
Growth Requirements
General
ʻŌhiʻa is a vital component of native landscapes and can thrive in urban environments with proper care. These trees require good sunlight, rich organic soil, and excellent drainage to flourish. Due to their near-constant blooming, they attract bees and other insects, so consider this when choosing planting locations near windows or entrances.
For container-grown ʻōhiʻa, ensure there is adequate drainage by using black cinder and provide full sun exposure. Fertilize at half strength as directed and avoid letting the plant become root-bound in pots. It is best to transplant them into the ground before this occurs.
Monthly foliar feeding with a water-soluble or organic fertilizer has proven beneficial for container plants. When planting ʻōhiʻa, dig a larger hole than the root ball, add drainage material, and avoid planting too deeply. Water thoroughly and consider using a B-vitamin solution to reduce stress and promote root growth.
ʻŌhiʻa trees are sensitive to root disturbance, so take care when planting and use extra caution not to spread out the roots. Water small plants daily until established, and larger plants every two to three days. Look for new growth as a sign of a successful planting, such as new leaves (liko). Trees grow quickly but may take years to develop a significant canopy.
When necessary, it is recommended to perform light and careful pruning on trees and shrubs, as this will not harm them. It is important to avoid excessive pruning at any one time. Take your time and prune over several weeks or months.
Koa, koaiʻa ʻiliahi, kōpiko, naupaka kuahiwi, and hāpuʻu, as well as dozens of other larger native shrubs and trees, are natural companion plants. Native ferns such as palapalai (Microlepia strigosa), kupukupu (Nephrolepis cordifolia), or niʻaniʻau (Nephrolepis exaltata) may be planted around or near the base of ʻōhiʻa that may have a somewhat shadier understory. For brighter or sunnier locations, use plants such as maile and ʻukiʻuki (Dianella).
Pests and Diseases
Caterpillars and Chinese rose beetles can wreak havoc on new growth. The black twig borer is a particularly troublesome pest. When dealing with infected material, it is crucial to cut well below the dead area, wrap it securely in a plastic bag, and dispose of it immediately. Whiteflies can also infest the trees.
ʻŌhiʻa is vulnerable to attacks by the bright yellow ʻōhiʻa rust, also known as guava rust (Puccinia psidii), especially in wet environments or during the rainy season. This aggressive rust can become a serious issue if not addressed promptly. At the first sign of ʻōhiʻa rust, it is important to carefully trim off the infected material, securely bag it, and dispose of it. One recommended method is to place the cut pieces in a bottle with a small amount of alcohol before disposal. Additionally, the affected plant and any nearby relatives (Eugenia spp., Syzygium spp.) should be treated with a fungicide immediately. Be sure to clean your tools with alcohol after trimming infected tree parts so as not to spread it to other plants. And, it is crucial to never add trimmings damaged by ʻōhiʻa rust or black twig borer to a compost pile.
Rapid ʻŌhiʻa Death (ROD) is a severe and deadly fungal disease that rapidly kills ʻōhiʻa trees. This devastating disease is caused by two aggressive fungi, Ceratocystis lukuohia and C. huliohia. Interestingly, the specific epithet lukuohia means to "massacre, destroy, slaughter, lay waste, devastate, exterminate, ravage" ʻōhiʻa; huliohia means to "turn, change, affect, overturn, convert, reform" ʻōhiʻa [Hawaiian Dictionaries]. DO NOT move ʻōhiʻa, or any parts of it, including lei, between islands. Refer to the Pests & Diseases page for treatments.
Uses
Ancient Hawaiian
Early Hawaiians utilized ʻōhiʻa in a variety of ways, showcasing the versatility of this exceptional wood. It was skillfully crafted into kapa beaters, prepping boards for kapa (lāʻau kahi wauke), poi boards (papa kuʻi poi), musical instruments, kālāʻau (dancing sticks), idols, spears, pāhoa (daggers), lāʻau (clubs), mallets, standards of kāhili, house construction, gunwales, and interior framework for canoes [Handy & Handy 1972, Krauss 1993, Medeiros et al. 1998, Neal 1965].
Lei making has been a cherished tradition in Hawaii, with flowers, seed capsules, and liko (new leaves) of ʻōhiʻa being used from ancient times to the present day. Lei ʻōhiʻa, whether made solely from this material or combined with others, were given names such as lei lehua ʻula (red flowers), lei lehua ʻalani (orange flowers), lei lehua melemele (yellow flowers), and lei liko lehua, which incorporated new leaves [McDonald & Weissich. 2003].
In traditional Hawaiian medicine, a concoction of ʻōhiʻa flowers, the inner bark of the indigenous hau (Hibiscus tiliaceus), and a small amount of water was administered to women during labor when the pains of childbirth became unbearable. Each time the woman experienced intense contractions, she would be given a mouthful of this mixture to drink [Krauss 1981]. Additionally, liko ʻōhiʻa were combined with lama leaves, leaf buds, and flowers to create a remedy for thrush in children. According to D.M. Kaʻaiakamanu, this mixture would be enhanced with poi lehua from kalo lehua, heated with hot stones, cooled, and strained before being given to the child [Ka‘aiakamanu 1998]. Liko was also used to improve the appetite and digestion of weak children [Handy & Handy 1972]. Kaʻaiakamanu, in his third volume, specifically mentions the use of "Metrosideros collina plym Glaberrima" in this treatment, noting that the "mother chews the liko" as well as pounds it before administering it to the infant [Ka‘aiakamanu 2003]. The aerial roots (aʻa lewa) of ʻōhiʻa were also utilized medicinally to stimulate appetite. [Gon 2013]
In addition to its medicinal properties, the wood of ʻōhiʻa was highly valued as a superior firewood [Medeiros et al. 1998].
Modern
The very hard, strong wood is much prized today for flooring, furniture, decorative poles, carvings, and ʻukulele keys. [Little & Skolmen 1989, Shafto & McDaniel 2009] Sapwood is pale brown, grading gradually into reddish-brown heartwood [Little & Skolmen 1989]. Wood takes a fine polish, but is difficult to cure [Nagata 1992].
Beautiful lei made with the flowers, buds and liko are still a favorite as they were in times of old [McDonald & Weissich. 2003].
Leaves are used still as a pleasant tea in folk remedies [Little & Skolmen 1989]. Because of the abundance of nectar, the plants are classed as a honey plant. Lehua or ʻōhiʻa honey (meli) has a unique flavor to it [Little & Skolmen 1989].
Special Features and Information
General
ʻŌhiʻa, belonging to the Myrtle family or Myrtaceae, is a diverse group with over 5,950 species. In Hawaiʻi, several non-native relatives that have become naturalized, such as myrtle, tea tree, strawberry guava (waiawī ʻulaʻula), pineapple guava (kuawa), allspice, eucalyptus, melaleuca (paper bark), bottlebrush (Callistemon spp.), and Surinam cherry (Eugenia uniflora). Unfortunately, some of these non-native species have become invasive, displacing native forests and creating monocultures that stifle biodiversity. One particularly invasive species is the strawberry guava (Psidium cattleianum), which forms dense canopies that prevent other vegetation from growing beneath it.
Among the native Metrosideros species in Hawaiʻi, there are five endemic species: Lehua ʻāhihi or ʻāhihi (M. tremuloides), lehua papa (M. rugosa), and three species known as ʻōhiʻa (M. polymorpha, M. macropus, and M. waialealae). But certainly, M. polymorpha is the most common and widespread ʻōhiʻa in the islands.
Additionally, there are other native Myrtaceae members in Hawaii, including the indigenous Beach cherry or nīoi (Eugenia reinwardtiana), and two endemic species: the endangered Koʻolau eugenia or nīoi (Eugenia koolauensis), and the fairly common ʻōhiʻa hā (Syzygium sandwicensis).
Several native Hawaiian birds, such as the ʻiʻiwi (Drepanis coccinea), ʻapapane (Himatione sanguinea), and ʻakohekohe (Palmeria dolei), can be found feeding on the flowers and foliage of ʻōhiʻa. These birds primarily consume flowers and insects, while others like the ʻakiapolaʻau (Hemignathus munroi) and ʻakialoa spp. (Hemignathus spp.) forage among the foliage. Unfortunately, the Black mamo or hoa (Drepanis funerea) and the ʻakialoa spp. are now extinct [Pratt 2005]. The coloration of these birds may have served as camouflage, protecting them from predators like the Wood harrier (Circus dossenus) and the stilt-owls (Grallistrix spp.), all of which are extinct. The extant Hawaiian hawk or ʻio (Buteo solitarius) may still pose a threat to these birds [Ziegler 2002].
As a key component of native Hawaiian forests, ʻōhiʻa often stands as a dominant or co-dominant tree. The number of natural habitats where ʻōhiʻa grows is simply staggering! Trees and shrubs can be found in or near coastal sites, dry, mesic and wet forests, wind-swept slopes and ridges, arid shrublands, sub-alpine, and even saturated mountain bogs perpetually shrouded by mist, where mature flowering ʻōhiʻa may grow only a few inches tall. They can even be commonly seen growing as an epiphyte on hāpuʻu (tree fern). ʻŌhiʻa are often the first to establish themselves on new lava flows, creating a welcoming environment for a variety of plants and animals seeking refuge. Their adaptability and resilience make them a vital part of Hawaiʻi's unique ecosystem.
Hawaiian Name
ʻŌhiʻa is the collective name for all the Hawaiian Metrosideros species (macropus, polymorpha, rugosa, tremuloides, waialealae). Lehua is the flower of the ʻōhiʻa tree, but also the tree itself Hawaiian Dictionaries. The ancient Hawaiians recognized distinctive forms of ōhiʻa (M. polymorpha). As an example, for the variety pumila, they gave additional names such as lehua maka noe, lehua neʻeneʻe, and lehua neneʻe.
Etymology
The generic name Metrosideros is derived from the Greek metra, heartwood, and sideron, iron, referring to the very hard wood of these plants [Gledhill 2008]. The specific epithet polymorpha is from the Greek poly, many, and morphos, forms, in reference to the numerous forms or shapes of this species [Gledhill 2008].
DWE