Native Plants of Hawai‘i - Xylosma hawaiense

Xylosma hawaiense

Salicaceae or Willow family

Synonyms: Drypetes forbesii, Drypetes sherffii, Xylosma hawaiense var. hillebrandii, Xylosma hillebrandii

Maua

Aʻe

Hawaiʻi brushholly

Natural Range & Environment

Xylosma hawaiense is endemic to all the main Hawaiian Islands except Ni‘ihau and Kaho‘olawe. (A second endangered species, X. crenatum, also called maua, is endemic to Kaua‘i.) From our observations, there seem to be at least two ecotypes of maua. On O‘ahu, maua is most common in mesic forests, while on Lāna‘i at Kānepu‘u and Hawai‘i Island in Kona, maua is commonly seen in dry open and closed forests. We are not familiar with its habitat on the other main Islands, but according to Wagner et al. [1990], maua occurs primarily in mesic forests, but also in dry woodlands and wet forests (250-)400 to 1,220 m ((820-)1,312 to 4,003 ft.) [Wagner et al. 1990].

In the past, maua, along with other native trees such as alaheʻe, hao, lama, ʻohe makai, and wiliwili, could be seen growing on or near dry Hawaiian coastlines [Culliney 2005]. Botanist Joseph Rock, in 1912, described the last pitiful maua in arid western Molokaʻi as "the remnant of what was once a beautiful forest" [Rock 1974].

The male maua flowers pictured here can be distinguished from female flowers by their many long stamens. A cluster of ripe fruits on a female tree. The new leaves of maua can be anywhere from dark red to bronze-green. Note the taller stature of this young cultivated maua from Hawai‘i Island dry forest stock and a young cultivated maua from Maui parentage (Maui tree photograph courtesy of Forest & Kim Starr CC BY 2.0). An old wild maua in Kona, Hawai‘i Island.

Description

Xylosma hawaiense is a long-lived (greater than five years) small to medium-sized (up to 30 ft; 10 m) tree with light gray bark that has a variable height-to-width ratio in cultivation; except for stunted out-in-the-open windswept trees, wild maua appear to be more standard in their appearance (see photographs above). Mature leaves are medium to dark green, glossy, with a toothed or untoothed margin, and tend to flutter in the wind. New leaves, a striking and beautiful feature of this species, range in color from dark red to bronze-green.

Maua is usually dioecious (i.e., male and female flowers are on separate trees) or rarely monoecious (i.e., male and female flowers on the same tree). Maua flowers develop in clusters along the stems, with male flowers essentially a mass of yellow to red stamens, while female flowers look like small immature fruits. Berries ripen from green to reddish-purple and are about one-third of an inch (0.8 cm) in diameter, each containing 1 to 3 irregularly-shaped black seeds. Wild maua usually bloom during the spring and summer, but this can vary according to location and environment; cultivated trees tend to bloom sporadically, often more than once a year.

Growth Requirements

General

The requirements below are for the dry forest Xylosma hawaiense ecotype.

Xylosma hawaiense grows best in a site with full sunlight for all or most of the day, and does poorly in constant shade. While this ecotype has good drought tolerance, it should be watered regularly (once a week) for several months after planting. Once established, reduce your watering to once a month or less depending on the rainfall at the planting site; do not overwater since this may cause root rot. Maua doesn't seem to be picky about soil type and will grow in lava/cinder, clay, or organic-dominant soils, provided the soil drains well; we have not tried to grow it in sandy or coralline soils.

During the cooler winter months, new plants can grow quickly, often branching low down on the main trunk. This is a good time to apply a balanced controlled-release fertilizer to further hasten growth. A support pole can help prevent toppling or broken branches during strong winds. After two to three years of good growth, you should have a small tree three to six feet (1 to 2 m) tall. This is when flowering starts, and you discover if you have a male or female tree. Obviously, if you intend to harvest seeds from your maua (to give to all your friends, of course), you’ll need to plant more than one and be lucky enough to have at least one male and one female tree. Maua often grow slower after they start flowering. However, because larger maua are more resilient than smaller trees, we encourage you to promote maximum growth with regular (but not extreme) fertilizing.

Avoid pruning your maua except to remove dead branches, prevent it from toppling over in a windstorm, or create a shade tree. If you do prune, do so gradually, removing only one or two branches and then waiting a few months before pruning again.

Pests and Diseases

Young maua are sometimes attacked by broad mites, while older trees appear to be more resistant. Still, keep watch for any symptoms of infestation. Root mealybugs can be a serious problem and should be dealt with quickly; regularly inspect the soil at the base of your plant for this pest. Black twig borers can kill a young maua or the branches of older trees. These attacks can be severe during times of stress caused by drought, inadequate light, or another pest. Refer to the Pests & Diseases page for ways to combat the above-mentioned pests.

Over the years, I (Koebele) have lost several maua within weeks to — I think — a soil-borne fungus or bacterium. Changes in watering, both increasing and decreasing, have preceded some of these quick deaths. Therefore, the best advice we can currently give is to proceed slowly with any changes in watering.

Uses

Ancient Hawaiian

The Bishop Museum Hawaiian Ethnobotany Online Database states that maua was "Good for boards," and references "Malo 1951;22." So far, we have been unable to find this statement in Malo [1898/1903], and it is unclear what Malo 1951; 22 is a reference to. However, according to Lamb [1981], maua wood may have been fashioned into boards on which poi was pounded.

Modern

Special Features and Information

General

Recently, the Salicaceae or Willow family was expanded to include the tropical Scyphostegiaceae family and many of the former Flacourtiaceae family. With these inclusions, Salicaeceae now contains about 1,220 species within 56 genera [WikipediA;Salicaceae].

There are two species of maua (Xylosma spp.) endemic to Hawai‘i, with Xylosma hawaiense being the more common and widespread of the two. Rare and endangered, Xylosma crenatum is known from only 16 populations on Kaua‘i with a total of 37 individuals; the largest population has seven plants [USFWS 2020].

Hawaiian Name

Aʻe is the name for this species on Maui. Hawaiians also used the name a‘e for all the native Zanthoxylum species, as well as an alternative name for mānele (Sapindus saponaria). Maua also means "failure to give a return gift; ungrateful, close-fisted; a type of prayer for luakini dedication" [Pukui & Elbert 1986]; however, it's unclear if these meanings have any relationship to Xylosma hawaiense.

Etymology

Xylosma is from the Greek words, xylon, meaning "wood," and osma, meaning "odor" [Wagner et al. 1990]. The species name, hawaiense, is a direct reference to the observation that maua is native to the Hawaiian Islands. The suffix -ense was added to Hawaiʻi to Latinize the name [Gledhill 2008].

BPK