From Common Forest Trees of Hawaii

Prosopis pallida
Pea family (Fabaceae)

Post-Cook introduction

Kiawe or algarroba, an introduced usually spiny tree, is one of the most common trees and perhaps most useful of the dry lowlands of Hawaii. Recognized by the short trunk and wide spreading thin of small twice leaves and by the beanlike narrow, slightly flattened, yellowish pods. Mimosa subfamily (Mimosoideae).

©2018 Zoya Akulova
Small to medium-sized tree 30–60 ft (9–18 ) tall) with trunk 1 1⁄2 ft (0.5 ) or more in diameter, usually smaller, often angled and fluted, twisted, and crooked, and with widely forking branches. Bark gray brown, finely fissured. Outer bark brown, inner bark orange brown, fibrous, bitter. Twigs green, hairless, slightly zigzag, the or joints at leaf bases often with 1–2 spreading spines to 1 inch (2.5 ) long.

Leaves on long twigs or short spurs, dull light green and often finely hairy, 3 inches (7.5 ) or less in length, consisting of short axis less than 1 inch (2.5 ) long and 2–3 pairs of side axes 1–1 1⁄2 inches (2.5–4 ) long, with dot between each pair. are many (8–11 pairs), stalkless, narrowly oblong, about 1⁄4 inch (6 ) long and less than 1⁄8 inch (3 ) wide, rounded at rounded and unequal-sided at base, thin.

Flower clusters (spikes) lateral, 3–4 inches (7.5–10 ) long and 5⁄8 inch (1.5 ) wide, unbranched, hanging down. Flowers very numerous, crowded, light yellow, about 1⁄4 inch (6 ) long, composed of cuplike green five- of five narrow petals, 10 threadlike and narrow with hairy curved threadlike and dot Flowering mainly in spring and summer.

(pods) few hanging from slender stalks, beanlike, yellowish, narrow and slightly flattened, 3–8 inches (7.5–20 ) long, 3⁄8 inch (1 ) wide, and 3⁄16 inch (5 ) thick, long-pointed, not splitting open, with whitish slightly sweet pulp. Seeds 10–20, each within a whitish four-angled cover, beanlike, elliptical and slightly flattened, 1⁄4 inch (6 ) long, shiny light brown.

Wood is dark reddish brown, very heavy ( gr. 0.85), extremely hard, and has low shrinkage in drying. In Hawaii, it has been made into cement floats and mallets, as well as heavy rifle stocks in match shooting. Its most common uses are charcoal, fuelwood, and fence posts. The heartwood is very resistant to decay. Though attacked by marine borers, the timber has served for piling elsewhere. The bark reportedly contains tannin and yields a brownish gum suitable for varnish, glue, and medicine.

Kiawe is one of the most useful introduced trees of Hawaii, primarily because it occupies barren lands that are otherwise unproductive. The pods serve as valuable feed for livestock in rangelands and are harvested for this purpose. It is reported that a mature tree bears up to 200 pounds (91 kg) of pods annually. The foliage is also eaten. Flowers are an important source for bees. Following the introduction of honeybees in 1857, Hawaii exported 200 tons (182 t) of kiawe honey a year. At present, most honey is produced on Niihau and Molokai.

This species has become established as the most common tree in the lowland dry zone of Hawaii from sea level to about 2000 ft (610 ) altitude. It covers an estimated 90,000 acres (36,473 ha) of barren soils throughout the islands. It grows on coastal sand, old lava flows, and clay soils with rainfall as low as 10 inches (250 ) per year. It is not salt tolerant and is defoliated by salt spray from winter storms.

Though large trees are ornamental and grow rapidly, planting near buildings is not recommended. The trees have shallow root systems and may be uprooted during storms. Also, and more importantly, the large thorns on twigs that fall from the trees make walking barefoot beneath the tree very hazardous and painful. The thorns readily penetrate soft-soled shoes.

Introduction of this species has been traced to seed from a Peruvian tree growing in the royal garden at Paris (Judd 1916). The seed was planted by Father Bachelot in 1828 in the Catholic Mission ground in Honolulu. By 1840 It was common as a shade tree throughout Honolulu, which prior to the introduction of this tree was almost treeless. For many years it was identified as Prosopis juliflora (Sw.) DC., a related species with a broader distribution in tropical America, and as P. chilensis (Moll.) Stuntz, of Chile. Continued selling over the years has resulted in distinct genotypes showing up frequently, for example, a spineless variety. Kiawe is present on all the islands. One of the oldest trees in Honolulu stands in front of Kawaiahao Church. It was a good size tree when photographed in 1855. A portion of the stump of the original tree is displayed at the Catholic Church on Fort Street, close to the site where It grew until 1919.

Special area

Height 91 ft (27.7 ), c.b.h. 13.4 ft (4.1 ), spread 81 ft (24.7 ). Puako, Kawaihae, Hawaii (1968).

Native of dry Pacific coastal region of Ecuador, Peru, and Chile. Introduced from Hawaii to Australia, South Africa, and other tropical areas. Naturalized also in Puerto Rico and Virgin Islands.

Other common names
mesquite; algarroba (Spanish); bayahonda (Puerto Rico)

stamen -- the pollen-producing reproductive organ of a flower; The stamen consists of an anther supported by a filament.

sp. -- The abbreviation for "species". The plural is "spp". When used it sometimes means that the exact species is unknown. For example, "Aster sp" would mean some species within the Aster genus but the writer may not know exactly which species.

cm -- A centimeter which is about 0.4 inches.

m -- A meter is about 10% larger than a yard.

Glands are plant structures that secrete liquids, salts or other substances. Glands often appear as hairs with a drop of liquid at the end.

stigma - The tip of a pistil that receives the pollen.

style -- This is a long and thread-like structure that connects the stigma with the ovary. A flower may have a single style, or several of them.

The apex is the tip or the furthest point from the attachment.

alternate -- leaves alternate along the main stem and are attached singly.

Like the teeth on a saw, leaves and other surfaces can have toothed edges.

A pistil is the female structure of many flowers. It contains one or more carpels. Each carpel contins an ovary, style and stigma. The stigma receives the pollen which grows thru the style to reach the ovary.

Bipinnate -- A compound leaf with two rows of leaflets where those leaflets are again compound with two rows of leafelets.

node -- The point at which there is attached growth, as in the place where each leaf is attached.

deciduous plants are those that lose all of their leaves for part of the year.

fruit -- any seed-bearing structure in flowering plants. It is formed from the ovary after flowering.

A leaf is compound when multiple leaflets are on the same stem.

canopy -- The foliage of a tree; the crown. Also the upper layer of a forest.

leaflets -- Each little leaf-like thing in a compound leaf is a leaflet.

nectar -- A sweet fluid produced by the nectary in flowers and collected by bees and other insects.

Irregular flowers, such as those of the violet or the pea, are often bilaterally symmeteric. These flowers typically have petals of unequal size or shape.

mm -- millimeter. About 1/25th of an inch.

corolla -- The name for all the petals of a flower taken together.

calyx -- the sepals of a flower, typically forming a whorl that encloses the petals and forms a protective layer around a flower in bud.

An ovary is a part of the female reproductive organ of the flower. Above the ovary is the style and the stigma, which is where the pollen lands and germinates to grow down through the style to the ovary.