Native Plants of Hawai‘i - Sophora chrysophylla

Sophora chrysophylla

Fabaceae or Pea family

Synonyms: Edwardsia chrysophylla, Edwardsia chrysophylla var. glabrata, Edwardsia unifoliata, Sophora chrysophylla subsp. circularis, Sophora chrysophylla var. circularis, Sophora chrysophylla var. elliptica, Sophora chrysophylla subsp. glabrata, Sophora chrysophylla var. glabrata, Sophora chrysophylla subvar. grisea, Sophora chrysophylla var. grisea, Sophora chrysophylla f. haleakalaensis, Sophora chrysophylla var. kanaioensis, Sophora chrysophylla var. kauensis, Sophora chrysophylla var. lanaiensis, Sophora chrysophylla f. lualailuaenis, Sophora chrysophylla var. makuaensis, Sophora chrysophylla f. mauiensis, Sophora chrysophylla subvar. mauiensis, Sophora chrysophylla f. maunakeaensis, Sophora chrysophylla f. maunaloaensis, Sophora chrysophylla f. obovata, Sophora chrysophylla f. obtusa, Sophora chrysophylla subvar. obtusa, Sophora chrysophylla f. olindaensis, Sophora chrysophylla f. ovata, Sophora chrysophylla subvar. ovata, Sophora chrysophylla var. ovata, Sophora chrysophylla subvar. ovatifoliolata, Sophora chrysophylla f. parva, Sophora chrysophylla f. puuwaawaaensis, Sophora chrysophylla subsp. unifoliata, Sophora chrysophylla var. unifoliata, Sophora grisea, Sophora lanaiensis, Sophora unifoliata, Sophora unifoliata var. elliptica, Sophora unifoliata var. kanaioensis

Māmane

Mamani

Natural Range & Environment

Sophora chrysophylla is endemic to all the main Hawaiian Islands except for Ni‘ihau and Kaho‘olawe. However, it is rare on Kaua‘i, O‘ahu, and Lāna‘i. It is found in a wide variety of habitats, being scattered in lowland dry shrublands and forests to montane mesic or rarely wet forests, and is a dominant element of subalpine communities on East Maui and Hawai‘i Island, from 450 to 3,240 m (1,476 to 10,630 ft) [Wagner et al. 1990].

Māmane's bright yellow pea-like flowers and oddly constricted fruits typically develop in clusters (Photographs courtesy of Matthew Salkiewicz CC BY-NC 4.0.). On Maui and Hawai‘i Island, māmane seeds are bright yellow to orange, while on O‘ahu the seeds are dark brown (Photograph courtesy of Forest & Kim Starr CC BY 3.0 US.). My ONLY photograph of a semi-cultivated māmane, now dead; this O‘ahu plant was about three-years-old and three feet tall. Here, Kim Starr stands near an old wild māmane in Haleakalā National Park, Maui (Photograph courtesy of Forest & Kim Starr CC BY 3.0 US.).

Description

Sophora chrysophylla vary in form, from small to large shrubs (e.g., in dry open regions of North Kona, Hawai‘i Island) to small lanky trees (e.g., in the closed dry forests of the Wai‘anae Mountains, O‘ahu) to 'proper' trees supposedly up to 15 m (49 ft) tall (e.g., in open subalpine regions of East Maui and Hawai‘i Island); we have never seen a māmane more than about 30 ft (9 m). Wild plants have a lifespan well beyond five years. Māmane bark is typically gray and smooth when young, becoming furrowed or scaly on old trees. Its wood is dark, dense, and durable.

Sophora chrysophylla leaves are odd-pinnately compound with as many as 20 leaflets. They can be densely covered with hairs, giving the leaf a grayish-green look, or nearly hairless, in which case, the leaf is a more standard green color.

Māmane has pale to bright yellow pea-like perfect (bisexual) flowers that develop in clusters which hang down from the stem. Observers have reported different flowering periods for māmane at different locations. On O‘ahu, the wild māmane we’ve seen typically flower in winter or spring, which is similar to most reports from Maui, while on Hawai‘i Island most of the flowering seems to occur during summer and fall.

Pollinated flowers develop into long winged pods that are oddly constricted between each seed chamber. The pods turn from green to grey when ripe and remain on the plant for a very long time after ripening. The elliptical seeds are about ¼ in (6 mm) long and vary in color based on geography; seeds of Maui and Hawai‘i Islands plants are usually yellow to orange, while seeds of O‘ahu and Kaua‘i plants are brown to black. Māmane seeds are poisonous to most animals, with one important exception, the endangered palila (Loxioides bailleui; a native Hawaiian honeycreeper) which relies on immature māmane seeds for about 90% of its diet [DLNR;Palida].

Growth Requirements

General

Sophora chrysophylla is deceptively difficult to maintain. This is because, while scarred māmane seeds sprout quickly and the seedlings consistently grow at a moderate pace for about six months in the nursery (reaching about one foot [30 cm] in height), things also consistently go sideways after this. The māmane, both O‘ahu and Hawai‘i Island forms, I (Koebele) have grown in the nursery past their six-month birthday, go through repeated cycles of dieback (e.g., leaf loss) and regrowth. They fail to respond (well or badly) to fertilizer, and ultimately die within two years. The māmane I have planted in the ground typically follow a similar behavior to those in the nursery (i.e., repeated cycles of dieback, followed by death). The few exceptions I've had were plantings in restoration sites, where the plants grew larger and lasted longer but, also, ultimately died within about five years. Only one of my māmane has ever flowered, a three-year-old plant (see photograph above) planted in a Nānākuli Valley restoration site; it too died about a year after flowering.

The above-described experiences suggest (to me) two hypotheses: (1) there is something, perhaps a microbe, in the soil (that also makes its way into the potting media) that attacks the young māmane and eventually kills it, or (2) there is something missing, again possibly a microbe, from the soil (and potting media), that māmane needs to survive and grow long-term. Possible evidence for the first hypothesis is that my more isolated māmane (sometimes) lived longer than those planted (or kept in pots) in more lowland settings; it took longer for the microbe to "find" these isolated plants. Possible evidence for the second hypothesis is that māmane is a legume (Fabaceae) which are well-known to host symbiotic nitrogen-fixing bacteria called rhizobia in their roots that help the plants grow; koa and koai‘a are good examples of native trees that harbor these bacteria and benefit from the association. It is also possible that māmane symbiotically host a specific species or variety of mycorrhizal fungi (connected to their roots) that is required for their long-term survival and growth.

Some may argue that māmane requires a cool climate in order to grow to maturity and great age, based on their natural distribution being most prevalent in cooler habitats like Haleakalā on Maui and Mauna Loa and Mauna Kea on Hawai‘i Island. However, this doesn't explain why māmane are seen in warmer sites such as North Kona (Hawai‘i Island), Nānākuli Valley (O‘ahu), and Lāna‘i. Nor does it explain why māmane was/is recorded growing nearly at sea level (just above 100 ft) [Allen & Murakami 1999; Elbert & Skolmen 1989]. Rather, it's more likely that the cooler climate either promotes the presence and growth of beneficial microbes, or inhibits the spread or growth of harmful microorganisms.

In conclusion, we have our work cut out for us, with at least a few formal experiments, to figure out what is killing māmane in cultivated settings, and how we can overcome this depressing obstacle. If you have had better success with māmane than us, please contact us at EickhoffandKoebele@gmail.com, and share your manaʻo so that we might share it with others via this website.

Pests and Diseases

Few pests have bothered my (Koebele) māmane prior to their untimely death (see above discussion). Occasionally, Chinese rose beetles would chew off the small leaflets or a stem will be killed by a black twig borer. Small plants would infrequently become infested by hibiscus snow scale or spider mites. Refer to the Pests & Diseases page for ways to deal with these pests.

Uses

Ancient Hawaiian

Degener [1973] (quote below) does a very good job of describing most of the ways Hawaiians used māmane. And, his claims are supported by the reports of others, such as Handy & Handy [1972], Krauss [1993], Lamb [1981], and Neal [1965].

The wood of the mamani is very hard and durable. It was used by the Hawaiians as a substitute for the more valuable and rarer kauila wood in the making of agricultural implements and adz handles. It was sometimes used for the posts and beams of their houses. Often the sap wood of such timbers was carefully cut away, as that is not as strong and durable as the older, heartwood. During certain religious ceremonies to ward off evil, the high priest or kahuna nui, would hold in his hand a piece of mamani or kauila wood wrapped in dark kapa as a symbol of his authority.

Mamani wood was preferred for the making of the runners of the Hawaiian sled, or papa holua. These sleds were often twelve feet long, having the runners spaced as little as two and a half inches apart at the base and about six inches apart at the top where the body of the rider was to lie. Before using, the runners were lubricated with the oil expressed from the kernel of the kukui nut. With these sleds the chiefs amused themselves by sliding at great speed down certain courses, about eighteen feet wide, that extended from a steep hill onto the plain below. These courses were first paved with flat rocks and then covered with earth that was beaten hard. A layer of dry grass, because of its slipperiness, was then laid on top.

In more recent times, the ranchers cut the trunks of the mamani trees into fence posts because of their great durability in the soil.

Other ancient uses of māmane include:

The bright yellow flowers were used in lei-making [Krauss 1993; McDonald & Weissich 2003].
Māmane flowers were used as astringent [Krauss 197-]
Summers [1990] states that māmane were among the woods used in making lā’au kahi olonā or papa olonā, the long slender thin hardwood boards used for scraping olonā.

Modern

Post-contact uses of māmane include:

Wood was used for fences, wagon wheels, and frames [Lydgate 1883].
Māmane flowers and seeds are still strung into lei [McDonald & Weissich 2003].

Special Features and Information

General

Fabaceae contains numerous agriculturally important plants, and is the third-largest land plant family in number of species, behind only the Orchidaceae and Asteraceae, with about 765 genera and nearly 20,000 known species [WikipediA;Fabaceae]

There are about 50 species in the genus Sophora, with māmane being the sole representative in Hawai‘i [Flora of the Hawaiian Islands]. Some interesting non-Hawaiian species in the genus are several yellow-flowered species from New Zealand known as kōwhai (Māori for yellow); the fascinating yellow necklace pod (S. tomentosa) with constricted round seed pods; and toromiro (S. toromiro), the last of the endemic trees from Rapa Nui (Easter Island) that was barely saved from extinction [WikipediA;Sophora].

Māmane leaf buds, flowers, and particularly the green seed pods, are the main food sources of the palila (Loxiodes balleui), an endangered honeycreeper, today restricted to the māmane and naio shrublands and forests on Mauna Kea, Hawaiʻi Island. The palila once had a much larger range on Hawaiʻi Island, all the way to the eastern slopes of Hualālai and northwestern slopes of Mauna Loa. Fossil records indicate it also once inhabited the dry lowland forests of Oʻahu and Kauaʻi [Pratt 2005].

The yellow and green coloration of palila may have served as camouflage among the māmane trees, protecting it in prehistoric times from predators such as the wood harrier (Circus dossenus), stilt-owls (Grallistrix spp.), and (possibly) a hawk (Buteo sp.) on Oʻahu — all today extinct [Ziegler 2002].

Māmane is fire tolerant, with seedlings often sprouting after a fire. However, it cannot survive being constantly fed upon by feral goats and sheep, which have significantly reduced māmane populations in post-contact times [Stone & Pratt 1994].

Hawaiian Name

The name mamano is used by Little Jr. & Skolmen [1989]. However, mamano is absent from all the Hawaiian dictionaries we checked.

Etymology

Sophora is derived from an Arabic name, sophera, for a pea-flowered tree [Gledhill 2008]. The species name, chrysophylla, comes from the Greek words, chryso, meaning "gold" or "yellow" and phylla, meaning "leaves or leaflike parts" [Merriam-Webster], likely a reference to the abundant yellow flowers of māmane.

BPK