Alphitonia ponderosa
Rhamnaceae or Buckthorn family
Synonyms: Alphitonia ponderosa var. auwahiensis, Alphitonia ponderosa var. costata, Alphitonia ponderosa var. grandifolia, Alphitonia ponderosa var. kauila, Alphitonia ponderosa var. lanaiensis
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Kauila
Kauwila, Oʻa (Maui)
Natural Range & Environment
Alphitonia ponderosa is endemic to all the main Hawaiian Islands except for Ni‘ihau and Kaho‘olawe. It occurs in dry to mesic forests from 240 to 1,250 m (787 to 4,101 ft) and is rare throughout its range except on Kauaʻi [Wagner et al. 1990].
Similar to maua (Xylosma hawaiense), based on my (Koebele) field observations, there may be two Alphitonia ponderosa ecotypes, one best adapted to mesic (wetter) conditions (prevalent on Kaua‘i) and the second better adapted to dry areas. However, based on my limited cultivation experiences and field observations, both ecotypes seem to grow better under cool upland conditions than in the hotter lowlands.
The mature fruits of Alphitonia ponderosa look a lot like black acorns (to all of us Mainland transplants) (Photograph courtesy of Kenneth R. Wood [NTBG] CC BY-NC 4.0.). While the fruits and seeds of both kauila species are about the same size, A. ponderosa seeds have a thin dry reddish aril (a covering around the seed) while Colubrina oppositifolia seeds do not; shown here is a ripe A. ponderosa fruit, three seeds with aril and three seeds with aril removed. The growing tips of A. ponderosa often have a reddish tint (Photograph courtesy of Forest & Kim Starr CC BY 3.0.). Cultivated kauila begin flowering and fruiting when still quite young and small (Photograph courtesy of Forest & Kim Starr CC BY 2.0.). Two old wild A. ponderosa, a towering giant on Kaua‘i and a considerably shorter tree on Maui (Photograph of Kaua‘i tree courtesy of Kenneth R. Wood [NTBG] CC BY-NC 4.0; photograph of Maui tree courtesy of Forest & Kim Starr CC BY 3.0.).
Description
Alphitonia ponderosa is an increasingly rare (except on Kaua‘i) long-lived (greater than five years) medium-sized to large (up to 82 ft [25 m]) tree; trees are typically medium-sized in dry locations and large in mesic habitat. It has white to gray corrugated bark (particularly in dry habitats) and a very dense light red sapwood and dark red heartwood which fades when cut and aged.
The leaves of Alphitonia ponderosa are ovate to lance-like, typically about 3 to 5 inches (8 to 13 cm) long, and often slightly crinkled, with a dark green somewhat glossy hairless upper surface and a dull whitish to rusty lower surface. The leaf's major veins are normally prominent on both the upper and lower surface. When emerging and young, leaves are frequently covered in a dense rusty to white fuzz that may or may not persist with age on the lower surface.
Clusters of small, perfect (bisexual), star-shaped, light green to white flowers develop near the stem tips (see header photograph). The species doesn't seem to have a defined flowering season, and flowers can be seen on wild trees throughout the year.
Pollinated flowers develop into ovoid green fruits, turning to black when ripe and resembling the acorns of mainland oak trees. The ripe fruits are dry with a mealy mesocarp (middle-flesh). Within each fruit are one to three oblong shiny dark brown to black seeds, each covered with a reddish parchment (i.e., a dry thin aril) (see photograph above).
Growth Requirements
General
Note: The discussion below is in regard to plants grown from seed collected from Alphitonia ponderosa growing in dry forests on Maui and Hawai‘i Island. We have not grown the mesic forest ecotype prevalent on Kaua‘i.
Alphitonia ponderosa has proved to be a real challenge (for me, Koebele) to keep longterm in a landscape. Over the years, I have grown this species numerous times and have yet to brag about a tree that was taller than myself. While propagating (by seed) and growing seedlings to a plantable size (1 to 2 feet [30 to 61 cm]) has never been very difficult (see Native Hawaiian Garden), once in the ground, each and every one of my kauila has died due to sometimes recognizable and sometimes unknown reasons.
Likely, the primary reason for the eventual death of all my Alphitonia plantings is they grew too slowly to outgrow the environmental and pest threats they faced. This is something John Culliney and I recognized a long time ago [Culliney & Koebele 1999]; we saw that potted Alphitonia exposed to high media temperatures during the summer stopped growing. Therefore, I recommend planting your Alphitonia in a cooler upland location (i.e., above 1,000 ft), or, if that's not an option, do your best to keep the soil surrounding your plant as cool as possible with both/either midday misting and strategic shading (e.g., planting on the eastern side of a building so your tree is shielded from the afternoon sun).
All my Alphitonia plantings were in sites that received full sunlight for all or most of the day. I did this based on where I had seen mature wild trees growing. However, in hindsight, these placements were probably a mistake, and it would have been better to plant my young kauila in a more shaded spot, perhaps beneath a large shrub that it would eventually grow above, or as mentioned above, the eastern side of a building.
While Alphitonia ponderosa can survive drought, young plants in the ground visibly suffer (e.g., wilted leaves, leaf loss) when they don't receive enough water and will enter a period of stasis until the soil once again becomes moist. (Unfortunately, several of my restoration plantings were killed by drought.) Therefore, keep the soil (or media) surrounding your kauila moist, but not wet, at all times so your young tree remains unstressed and constantly growing.
In keeping with the goal of getting your Alphitonia to grow as quickly as possible, you should regularly fertilize your young tree. Do this by applying a controlled-release fertilizer every six months, or by using a foliar organic or inorganic fertilizer at ⅓ to ½ the recommended strength every couple of months.
While cultivated Alphitonia grow slowly, they, like the other kauila (Colubrina oppositifolia), begin flowering and fruiting at a surprisingly young age (i.e., 2 to 3 years) and small size (i.e., sometimes less than two feet [61 cm] tall). My oldest Alphitonia was nearly five feet (1.5 m) tall before it perished (for an unknown reason). It was about ten years old. The only cultivated Alphitonia I've ever seen that was taller was a six to seven foot tree at Lyon Arboretum on O‘ahu. It died many years ago; I don't know why. If you have had better success growing Alphitonia ponderosa, please contact us and share your mana‘o so that we might update this webpage and share your discoveries with other native Hawaiian plant enthusiasts wishing to grow this species. You can contact us as: EickhoffandKoebele@gmail.com.
Pests and Diseases
Black twig borers are the most serious recognizable threat to Alphitonia, and require vigilance to keep them controlled. Small kauila (i.e., less than 3 feet [1 m] tall) are particularly vulnerable since a lone borer can kill the main stem. And, unlike the other kauila (Colubrina oppositifolia), which will often put out new shoots from the remaining live stem below the borer hole and recover, small Alphitonia rarely do this and ultimately die. For larger Alphitonia, borers can slow their growth by killing their thinner side branches.
Several factors regulate the amount of damage caused by the black twig borer to kauila. First, there is the plant’s location. Expect the most damage in windless sites. Second is the health of the tree. Keep your young kauila watered enough to keep the surrounding soil moist, thereby avoiding drought stress, which can make your young tree more vulnerable to borer attacks. However, do not overwater your plant to the point that the soil is constantly wet, or you’re likely to face new problems from unfriendly soil microbes. Third is the prompt removal of infested branches. Black twig borer larvae within the dead branch take time to mature and then spread to new healthy branches. If you prune away and dispose of the infested branches quickly, you can break the cycle of infestation. Disposing of the branches means taking them far off-site — don’t just toss them on your compost pile.
Occasionally, whiteflies will infest the underside of a kauila's leaves and, if left untreated, can quickly overwhelm small trees. Scale insects, typically imported, farmed, and protected by ants, can also sometimes become a problem. Refer to the Pests & Diseases page for more information on the black twig borer, whiteflies, scale insects, and ants, and how to deal with each.
In addition to the above recognized pests, a few of my Alphitonia died for no apparent reason. Currently, my best guess is that the young trees were killed by a pathogenic microbe in the soil; this type of death obviously requires professional research. (I'm talking to you graduate students!) If this happens to your Alphitonia, I recommend trying again in another location as far away as possible from your dead kauila.
Uses
Ancient Hawaiian
Likely, because of the incredibly dense wood of both Alphitonia ponderosa and Colubrina oppositifolia, Hawaiians referred to both species by the same name, kauila (or kauwila). Therefore, it is currently impossible to determine if the two species were used differently in ancient times. The summary below is for uses of kauila and kauwila, and is not species-specific. A more detailed accounting can be found in Abbott [1992], Krauss [1993], and Mederios et al. [1998].
Pre-contact Hawaiians did not have regular access to metal. Therefore, the hard dense wood of kauila was particularly valuable in the construction of items that other indigenous people often made of metal, such as their finest tools and weapons, kāhili (tall feathered banners), the runners on sleds (papa hōlua), game pieces, musical instruments (ka lāʻau and ‘ukeke), images (ki‘i), and fishing lures (melomelo). Sometimes, hale beams were made of kauila, and kauila pegs were favored for repairing wooden bowls. Even kauila splinters were not discarded, but fashioned into hairpins. Lastly, a bluish dye was made from the bark and leaves.
Ka‘aiakamanu (1922 & 2003) states that kauila wood shavings, mixed with water, were used to treat several illnesses. However, this use is not mentioned by any other sources.
Modern
Post-contact (after 1778), kauila wood had some limited uses. For example: the lintels above the windows of the Hawaiian Missionary Printing House, built in 1821, were made of kauila wood and were still quite sound when removed for restoration in 1972 [Elbert & Skolmen 1989]. Today, the species is too rare for respectful woodworkers to collect and fashion, except, possibly, in the case of dead trees found on private lands.
Special Features and Information
General
Rhamnaceae is a large family of mostly trees and shrubs (and some vines) with about 950 species within 55 genera. They have a worldwide distribution and are most common in tropical and subtropical regions [WikipediA;Rhamnaceae]. In addition to Alphitonia ponderosa, other native members of the Buckthorn family include: the indigenous climbing shrub ānapanapa (Colubrina asiatica); the other endemic and endangered kauila or kauwila (Colubrina oppositifolia); and three endangered endemic species of Gouania [Flora of the Hawaiian Islands].
Alphitonia ponderosa is one of the hardest of all native woods and was used by early Hawaiians as a metal substitute since there were no readily available sources of iron, etc., in the Hawaiian Islands. When the wood is freshly cut, Colubrina oppositifolia, the other kauila, has a yellowish sapwood and a light reddish brown heartwood. In contrast, Alphitonia ponderosa is red throughout with light red sapwood and dark red heartwood. Unfortunately, when dried and aged, the color differences fade over the years, making them visually indistinguishable. Microscopic analysis offers a way to tell the two woods apart, but scientists and museum curators are reluctant to shave off the needed samples from rare artifacts. Therefore, for the time being, there will remain uncertainty in many cases as to which species was used for any particular artifact [Abbott 1992].
In the past, the wood of three species of trees on Mauna Loa, Molokaʻi, were rumored to be poisonous, but only from that location, and were used in black magic. The three trees were called kālai pāhoa; the others were ʻohe (Polyscias sp.) and nīoi (Eugenia sp.) [Pukui & Elbert 1986].
Hawaiian Name
The names kauila and kauwila are different spellings of the same name for this species and its close relative, Colubrina oppositifolia. Pukui & Elbert [1986] state that o‘a is a "Maui name for kauila (Colubrina oppositifolia), a tree. (Neal 541.)" However, there is no mention of o‘a on page 541 of Neal [1965]. Therefore, it is more likely that Rock [1974] is correct, stating that o‘a is a Maui name for Alphitonia ponderosa.
Etymology
Alphitonia is from the Greek word, alphiton, meaning "barley meal," in reference to the dry, mealy quality of the mesocarp (the middle portion of the fruit) of plants in this genus [Wagner et al. 1990]. The species name, ponderosa, is Latin for "heavy, large, ponderous," [Gledhill 2008] perhaps referring either to the density of kauila wood or the size of the tree.
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