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Species
Prosopis pallida (H. & B. ex Willd.) Kunth
IUCN
NCBI
EOL Text
The genus Prosopis is noted for its ability to root deeply (10). A Prosopis uelutina tree in Arizona was found with roots extending downwards 53 in (174 ft) into the ground (10). Kiawe seedlings produce strong, rapidly growing taproots that appear to be capable of deep extension and may share the deep rooting characteristic common to the genus. The species can grow on windy, dry sites, which suggests that its roots penetrate deeply to reach moisture. Trees on such sites are small. Trees on coastal plains where abundant, shallow groundwater is available reach large size, but are shallow-rooted and subject to windthrow (3,9).
Kiawe stumps often sprout after being cut. Some thornless trees have been propagated by air-layering of the mature branches, but only on an experimental scale. Kiawe cuttings can also be rooted under mist (5).
Germination is epigeal. Seedlings are usually found associated with animal droppings during and after rainy periods. In this highly fertile situation, seedlings grow rapidly, reaching 0.3 in (1 ft) in 3 to 4 months. Even in the absence of browsing animals, kiawe reproduces prolifically on abandoned city house lots containing older trees. Seedlings in such a situation can grow more than 1 in (3 ft) tall in the first year if rainfall is adequate. Seedling survival depends primarily on sufficient rainfall during 4 to 6 weeks after germination. The seedlings are also intolerant of shade.
Pods do not open on drying to release their seed as some other legumes do. Instead, seeds are released either by natural decomposition of the pods or by passage of the seeds through the digestive system of an animal. From 10 to 20 light brown seeds per pod are encased in a sticky, sugary pulp. Seeds are difficult to extract from the pods. It is possible, however, to obtain seed by running pods through a commercial meat grinder with 1-cm (0.4-in) holes (5). There are about 28,500 to 32,000 seeds per kilogram (13,000 to 14,500/lb). The seeds can be stored at ambient room temperature, protected from insects, for 9 months with little loss of viability (18). Germination is improved slightly by scarifying the seeds with hot water before sowing. Scarification with concentrated sulfuric acid for 10 minutes improved germination from 64 percent (without treatment) to 88 percent (18).
Many seeds are destroyed by insect pests. In Hawaii, a black beetle, Mimosestes amicus, bores into the pods that have fallen to the ground (16). In Puerto Rico, a Bruchid weevil attacks seed on the tree, causing seed from green pods on the tree to have a germination rate of only 59 percent, yellow pods on the tree only 40 percent, and pods on the ground only 6 percent (18).
In Hawaii, kiawe begins to flower when 3 to 4 years old. The tree can flower at any time of the year and frequently flowers twice a year. Usually, it flowers from January to March, but in some years with wet summers it also flowers heavily during September and October. The numerous small perfect flowers are borne in pale yellow spikes 7 to 10 cm (3 to 4 in) long and about 13 min (0.5 in) in diameter. Styles protrude from the corolla just before it opens, but when it is opened the style and the 10 stamens are about the same length. Flowers are insect pollinated. Kiawe is an excellent honey tree (3).
About 6 months after flowering and pollination, the pods ripen and fall to the ground in April and July, or in normally dry years, only in July. The pods are straight or slightly curved yellowish beans 7 to 20 cm (3 to 8 in) long by 8 min (0.3 in) wide; there are 350/kg (160/lb) (18).
The oldest kiawe trees in Hawaii of known age are at the entrance to Punahou School in Honolulu. This area was a treeless field in 1848. In 1918, trees on this site that were about 70 years old ranged from 61 to 104 cm (24 to 41 in) in d.b.h. and from 20 to 26 m (65 to 85 ft) in total height (9). This is a relatively wet area for kiawe, with an annual rainfall of 940 mm. (37 in) and abundant groundwater from a nearby spring.
At Waianae, Oahu, an area with 510 mm (20 in) annual rainfall, a tract of kiawe trees of unknown age yielded 226.8 m³ per ha (3,240 ft³/acre or 36 cords/acre). On Maui, a 2.4-ha (6-acre) area with 380 mm (15 in) rainfall yielded 365.4 m³ per ha (5,220 ft³/acre or 58 cords/acre) (9).
In Puerto Rico, on a dry, gravelly site (760 mm or 30 in rainfall), a 21-year-old planting had trees 25 to 36 cm (10 to 14 in) d.b.h. and 4.6 to 7.6 in (15 to 25 ft) tall (18).
In Honolulu, the original tree, when measured in 1916, at 88 years of age, was 99 cm (39 in) in diameter (8). But the champion kiawe tree in Hawaii is at Puako, Island of Hawaii, and measures 130 cm (51 in) d.b.h. and 27.7 in (91 ft) tall (1).
In a study of biomass production of other Prosopis spp. in southern California (5), several species, mostly from South America, were grown for 3 years at 1.2 in (4 ft) spacing and three levels of irrigation. These trees produced an annual average of 8.5 t/ha (3.8 tons/acre) of fresh biomass. Another study in Texas (19) determined that Prosopis natural stands yielded 19.3 t/ha (8.6 tons/acre) on deep upland soils and 36.1 t/ha (16.1 tons/acre) on deep bottom land.
In Puerto Rico, direct seeding in dry areas (760 mm or 30 in rainfall) gave poor survival, but planting of seedlings produced 67 percent survival despite a severe 6-month drought (18).
On windy or dry sites, kiawe grows as a shrub, or a small twisted tree only 3 to 5 in (10 to 16 ft) tall. It is usually layered where it grows in strong trade winds and lies along the slopes as a rounded bush.
Leguminosae -- Legume family
Roger G. Skolmen
Kiawe (Prosopis pallida), also known as algarroba or bayahonda, is one of the 44 species of Prosopis recognized. The genus has a confused taxonomy. Burkart's revision, used here, assigns the designation P. pallida to the species introduced into Puerto Rico and elsewhere in the Caribbean formerly called P. juliflora. Prosopis glandulosa, mesquite, also formerly included in P. juliflora and four to six other species grow as shrubs or trees over an extensive area of the Southwestern United States and Northern Mexico (2,7,10).
More than 60 700 ha (150,000 acres) of dry kiawe forests in Hawaii are descended from a single tree planted in 1828 at the corner of a church in Honolulu. That year, Father Bachelot, the first Catholic priest in the Hawaiian Islands, planted a tree that he had raised from a seed he had brought with him from Paris. The tree was later determined to be Prosopis pallida. In August 1832, the tree was found to be hearing fruit. By 1840, progeny of the tree had become the principal shade trees of Honolulu and were already spreading to dry, leeward plains on all of the islands (3,8,12).
Because the entire population of kiawe in Hawaii is originally from one tree, inbreeding has been intensive. One possible recessive characteristic of the population is thornlessness. Although most kiawe trees have thorns with strong spines often 2.5 cm (1 in) long, an estimated 25 percent of the mature trees produce only small, hard stipules rather than long, spikelike spines at the twig nodes. The thornless characteristic has been noted for years, and as early as 1937, Hawaii shipped seed from thornless kiawe trees to Cuba, Arabia, Australia, Fiji, and South Africa (3). Attempts have been made to breed for thornlessness, but have so far been unsuccessful. Thornless trees can be propagated by air-layering of mature twigs (13). Some other Prosopis spp. also exhibit thornlessness among individuals in the populations (10). Thomlessness can be seen in some or all of these other species when they are only 3 to 4 months old (4).
One report states that Prosopis spp. bear self-incompatible flowers (15). This is obviously not true of Prosopis pallida, or at least of that one individual Prosopis pallida originally introduced into Hawaii.
Another report mentions that in 1920, the U.S. Department of Agriculture's Experiment Station in Honolulu had imported seed and was growing seedlings of a number of other Prosopis spp. in an attempt to determine the identity of the tree common to Hawaii by comparison (14). No record exists of the disposition of these seedlings, but a possibility exists that they may have been outplanted. No hybrids are known in Hawaii, however.
In addition to kiawe, at least five other Prosopis species deserve consideration for use in and lands for firewood, forage, and cover (10). One of these, Prosopis alba, is the backbone of the Arizona nursery shade tree industry (4).
United States
Origin: Exotic
Regularity: Regularly occurring
Currently: Unknown/Undetermined
Confidence: Confident
License | http://creativecommons.org/licenses/by-nc/3.0/ |
Rights holder/Author | NatureServe |
Source | http://explorer.natureserve.org/servlet/NatureServe?searchName=Prosopis+pallida |