Native Plants of Hawai‘i - Canavalia hawaiiensis

Canavalia hawaiiensis

Fabaceae or Pea family [Five-minute families]

Synonyms: Canavalia galeata var. hawaiiensis, Canavalia iaoensis, Canavalia kauensis, Canavalia mauiensis, Canavalia rockii, Canavalia sanguinea

ʻĀwikiwiki

Puakauhi

Hawaiian jackbean

Natural Range & Environment

Canavalia hawaiiensis is endemic to Lāna‘i, Maui, and Hawai‘i Island. It is found in dry to mesic forests from 120 to 1,220 m (394 to 4,003 ft) [Wagner et al. 1990] but has also been used in restoration efforts on Kaho‘olawe [Forest & Kim Starr].

Like some of the other endemic Hawaiian Canavalia species, the pea-like flowers of C. hawaiiensis can vary somewhat in color (red flower photographs courtesy of ka_y_ak CC BY-NC 4.0; purple flower photograph courtesy of Matthew Kahokuloa, Jr. CC BY-NC 4.0).

ʻĀwikiwiki produce large, flattened pods (photograph courtesy of Jay Smart ©), each containing one to a few large seeds (photograph courtesy of J.B. Friday ©). The new leaves of C. hawaiiensis are typically a bronze color, turning green as they mature (photograph courtesy of Forest & Kim Starr CC BY 3.0 US). All ʻāwikiwiki have compound leaves with three leaflets (photograph courtesy of James Bailey CC BY-NC 4.0), and, while they don't have tendrils, they all love to climb fences (photograph here and in header courtesy of Jay Smart ©).

Description

Canavalia hawaiiensis is a rapid-growing but short-lived (probably less than ten years) climbing vine or liana, typically with numerous twining stems — Canavalia do not have tendrils — that can grow to more than 10 feet (3 m) in length. The older stems are light gray and slightly woody.

The compound leaves of Canavalia hawaiiensis are composed of three elliptic to egg-shaped leaflets, with each leaflet being about 3 inches (8 cm) long. New leaves are typically a bronze color, turning green as they mature. Both surfaces of the leaflets start off covered with hairs. However, as the leaf ages, the upper surface often becomes nearly hairless while the lower surface usually retains some hairs. Leaflet hairiness can also vary depending on environmental conditions, with fast-growing or well-watered plants usually having fewer hairs. The main veins of the leaflets are visibly impressed (indented) from the upper surface.

Canavalia hawaiiensis produces clusters of pea-like perfect (bisexual) flowers that range in color from red to purple, normally with a white spot or streak near the base of the corolla. Flowering is sporadic year-round, often with a peak in the wetter period(s) of the year. Pollinated flowers develop into large, compressed pods that turn black, dry, and woody when ripe. Each pod contains one to several (but usually just a few) large, elliptic and flat, tan to reddish brown seeds, each with a thick, hard seedcoat (see photograph above and Seeds of Hawaii).

Growth Requirements

General

Canavalia hawaiiensis is the middle-of-the-road when it comes to growth requirements for ʻāwikiwiki. It requires more water than C. pubescens (i.e., is less drought tolerant) but not as much as C. galeata. On the other hand, it is more prone to pest infestations than C. galeata but is not a bug-magnet like C. pubescens.

Canavalia hawaiiensis is a climber. Therefore, consider planting it near a fence or using a trellis. In the wild, it can be seen climbing up nearby trees and shrubs. However, it also does just fine with nothing to climb on, in which case it tends to sprawl out along the ground. It can also be kept in a container but requires frequent pruning of its rapidly growing stems.

This ʻāwikiwiki does best when grown in a site that receives full sunlight for all or most of the day. While it can tolerate a bit of shading, shaded plants may not flower as often as plants in full sunlight. Once established (after one to two months in the ground), Canavalia hawaiiensis is moderately drought tolerant, but it's safest to keep the soil (or media) moist at all times to prevent stress and maintain vigorous growth. C. hawaiiensis can tolerate extreme heat (provided it is well watered) and strong winds. Having only grown this species in rocky clay soil and cinder-rich media, where it did okay, I (Koebele) cannot say how it would do in other soil or media types.

Canavalia hawaiiensis grows quickly under optimum conditions (e.g., full sunlight and moist soil), and you can expect to see flowers in less than a year. Be sure to collect and store any seeds produced for future replacements since ʻāwikiwiki sometimes die quickly and unexpectedly. All Canavalia species can fix nitrogen (with the help of rhizobial bacteria). Therefore, your ʻāwikiwiki normally will not require nitrogen-containing fertilizers. I never fertilized my ʻāwikiwiki except when I kept them in a pot for an extended period (i.e., over a year), in which case I applied a balanced controlled-release granular fertilizer every six months.

Pests and Diseases

As mentioned above, Canavalia hawaiiensis seems to be less prone to pest attacks than some other ʻāwikiwiki, like C. pubescens. However, generally, when growing any native Hawaiian Canavalia, you should be prepared to deal with a diversity of pests. The most common and serious pests are lace bugs (see photographs below) and spider mites, which yellow and kill the plant's leaves. Aphids and stink bugs can also sometimes become a problem. And, in moist environments, snails, slugs, and cockroaches may eat the leaves and stems of your ʻāwikiwiki. Rats and mice may also get a taste for ʻāwikiwiki. The quickest and easiest way to eliminate stink bugs is by hand; wear gloves if you don't want your hands to smell terrible afterward. Cockroaches are best deterred by using a granular, broad-spectrum insecticide (see Ants on the Pests & Diseases page). For the other above-mentioned pests, refer to the Pests & Diseases page for different methods of control.

If the attacks on your ʻāwikiwiki by lace bugs or spider mites are frequent or severe, you may be tempted to use a more long-lasting control chemical like a systemic insecticide or miticide, respectively. However, using a systemic insecticide comes with a significant potential downside. Unfortunately, all the systemic insecticides easily available to the public in Hawai‘i contain imidacloprid, which is extremely deadly to bees. Therefore, you will need to decide, "Do I kill the bees in my neighborhood in order to more easily protect my ʻāwikiwiki, or do I work harder (e.g., inspect and spray more often) with shorter-lasting insecticides?"

Lastly, it's entirely possible that your pest problem gets out of control and your ʻāwikiwiki drops all or most of its leaves. Don't panic! There's a good chance your plant can recover if you immediately start and repeatedly treat the surviving stems with an insecticide or miticide.

Corythucha gossypii (cotton or bean lace bug) on the underside of a Canavalia pubescens leaf. Black spots are lace bug feces. (Photograph courtesy of Forest & Kim Starr CC BY 2.0.) While I (Koebele) never saw this pest on my C. hawaiiensis, I suspect I was just lucky.

Adult Corythucha gossypii (cotton or bean lace bug). (Closeup photograph courtesy of Forest and Kim Starr CC BY 3.0 US.)

Uses

Ancient Hawaiian

All the taxonomically recognized native species of Canavalia in Hawai‘i (currently six species) have the common Hawaiian names ʻāwikiwiki and puakauhi [Wagner et al. 1990]. Therefore, it's currently impossible to attribute species-specific ancient uses to most of the Hawaiian Canavalia species, the one exception being C. galeata (see Abbott [1992] and Ka‘aiakamanu & Akina [1922] below).

Here are all the ancient Hawaiian uses of ʻāwikiwiki and puakauhi we were able to find in the literature.

While permanent fish traps were typically made from the aerial roots of ‘ie‘ie (Freycinetia arborea), temporary, roughly-made traps were sometimes made from ʻāwikiwiki vines [Abbott 1992 for Canavalia galeata; Krauss 1993].
The frame of scoop nets were probably made from twisted ʻāwikiwiki vines, which were used to catch small rock pāoʻo (blennies and gobies) and ʻōpae (freshwater shrimp), often at night [Krauss 1993].
ʻĀwikiwiki flowers were used in lei-making [Krauss 1993].
Ka‘aiakamanu & Akina [1922] claim the entire plant, ʻāwikiwiki (Canavalia galeata), along with "mountain apple bark" and "the entire Cassia occidentalis plant," was used in a bath to treat "itch" and "ringworm and kindred skin diseases." Cassia occidentalis, now Senna occidentalis, is an introduced and naturalized shrub in Hawai‘i. However, Hawaiians may have used the native Senna, Senna gaudichaudii, in ancient times.

Modern

ʻĀwikiwiki flowers and seeds are used in lei-making [Hui Ku Maoli Ola].

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]. In Hawai‘i, there are about 25 native species and about 150 introduced and naturalized species [Flora of the Hawaiian Islands].

Hawai‘i currently has two taxonomically recognized introduced and naturalized Canavalia species, C. cathartica (maunaloa, popular for lei-making) and C. sericea (pohue or silky jackbean), as well as six endemic species.

Canavalia galeata — primary found in mesic forests on O‘ahu.
Canavalia hawaiiensis — seen in dry to mesic forests on Lāna‘i, Maui, and Hawai‘i Island.
Canavalia kauaiensis — primarily found in mesic forests on Kaua‘i.
Canavalia molokaiensis — an endangered vine seen in open dry sites, mesic shrubland, and the steep slopes of gulches on Moloka‘i.
Canavalia napaliensis — an endangered vine found in open dry sites and mesic forests on Kaua‘i.
Canavalia pubescens — an endangered vine seen in dry open lava fields and in dryland forest, grassland, and shrubland on Lāna‘i and Maui (and formerly on Ni‘ihau and Kaua‘i) [Wagner et al. 1990; Flora of the Hawaiian Islands].

Hawaiian Name

ʻĀwikiwiki is a reduplication of ‘āwiki, which means "to hurry, be quick, swift," possibly referring to the rapid growth of this plant [Pukui & Elbert 1986].

Etymology

Canavalia is derived from the Malayalam word, Kanavali, the local name for a related species in the Malabar region of Kerala, India [Wiktionany].

The species name, hawaiiensis, refers to Hawaiʻi Island, where this species is endemically found. The geographic suffix -ensis was added to Latinize the name.

BPK