Adenanthera pavonina: an underutlized tree of the humid tropics
Adenanthera pavonina (L.) (family Leguminosae, subfamily
Mimosoideae) has long been an important tree in Southeast Asia and the Pacific
Islands. Cultivated in home gardens and often protected in forest clearings and
village common areas, this useful tree provides quality fuelwood, wood for
furniture, food, and shade for economic crops like coffee and spices. The tree
has been planted extensively throughout the tropics as- an ornamental and has
become naturalized in many countries. The scientific name is derived from a
combination of the Greek aden, "a gland," and anthers, "anther"; alluding to the
aCircassianbeananthers being tipped with a deciduous gland The tree is known by
a host of common names, including red-bead tree, red sandalwood, and
Circassian-bean in English; raktakambal (India); saga (Malaysia); lope (Samoa
and Tonga); coralitos, peronias, and jumble-bead (Caribbean).
Botany
A medium- to large-sized deciduous tree, A. pavonina ranges in
height from 6-15 m with diameters up to 45 cm, depending upon location. The tree
is generally erect, having dark brown to grayish bark, and a spreading crown.
Multiple stems are common, as are slightly buttressed trunks in older trees. The
leaves are bipinnate with 2-6 opposite pairs of pinnae, each having 8-21
leaflets on short stalks. The alternate leaflets, 2.02.5 crn wide and 3 cm long,
are oval-oblong with an asymmetric base and a blunt apex, being a dull green
color on top and a bluegreen beneath. The leaves yellow with age.
Flowers are borne in narrow spike-like racemes, 12-15 cm long,
at branch ends. They are small creamy-yellow in color, and fragrant. Each flower
is star-shaped with five petals, connate at the base' and having 10 prominent
stamens bearing anthers tipped with minute glands.
The curved pods are long and narrow, 15-22 cm by 2 cm, with
slight constrictions between seeds, and dark brown in color turning black upon
ripening. The leathery pods curve and twist upon dehiscence to reveal the 8-12
showy seeds characteristic of this species. The hard-coated seeds, 7.5-9.0 mm in
diameter, are lens-shaped, vivid scarlet in color, and adhere to the pods. The
ripened pods remain on the tree for long periods and may persist until the
following spring. There are reportedly 1600 seeds per pound (Little and
Wadsworth 1964).
Ecology
This species is common throughout the lowland tropics up to
300-400 m. Adenanthera pavonina is a secondary forest tree favoring
precipitation ranging between 3000-5000 mm for optimal growth. Found on a
variety of soils from deep, welldrained to shallow and rocky, this tree prefers
neutral to slightly acidic soils. Initial seedling growth is slow, but rapid
height and diameter increment occur from the second year onward. The tree is
susceptible to breakage in high winds, with the majority of damage occurring in
the crown. Rapid resprouting and growth following storm damage has been recorded
in the Samoan Islands (Adkins 1994).
Distribution
Adenanthera pavonina is endemic to Southeast China and India,
with first reports being recorded in India The tree has been introduced
throughout the humid tropics. It has become naturalized in Malaysia, Western and
Eastern Africa and most island nations of both the Pacific and the Caribbean.
Uses
There are historical accounts from Southeast Asia and Africa of
using all parts of tree for traditional medicines (Burkill1966, Watt and
Breyer-Brandwijk 1962). Adenanthera pavonina is extensively cultivated as an
ornamental for planting along roadsides and in common areas. The fast growth and
spreading crown of light, feathery foliage offer attractive shade. Interplanted
field and tree crops (spices, coffee, coconuts), along field borders as part of
a windbreak or in plantation, A. pavonina is a valuable agroforestry species
(Adkins 1994, Clark and Thaman 1993).
Adenathera pavonina
Wood Products.
Adenanthera pavonina is esteemed for fuelwood in the Pacific
Islands, often being sold in local markets. The wood bums readily producing
significant heat, and is used in both above- and below-ground ovens. Good sized
fuelwood, larger than 11 cm in diameter, can be produced in five years. The wood
is hard and durable having red-colored heartwood with light-gray sapwood. It is
close-and evengrained, making it useful for constructing furniture, cabinets,
and decorative wood products (Benthall 1946, Clark and Thaman 1993). It is also
valued for home building.
Seeds.
Known as "food trees" in Melanesia and Polynesia, the seeds of
this tree are roasted over a fire and eaten by children and adults alike.
Nutritional studies have shown one quarter of the seed weight to be oil with a
high percentage of protein, and a fatty acid composition favoring high
digestibility for both humans and livestock (Balogun and Fetuga 1985, Burkill
1966). Historically, the seeds were used as weight measures for jewelry and
goldsmithing due to their small variation in weight (Benthall 1946, Burkill
1966). The bright red seeds are still used today in fashioning necklaces and
decorative ornaments.
Foliage.
The small leaves breakdown easily making for good use as a green
manure. As a supplemental source of fodder, the leaves are fairly high in
digestible crude protein (1722%), but low in mineral content (Rajaguru 1990).
Silviculture
The tree is cultivated from seed. The seed coat is extremely
hard and requires scarification if even germination is to occur. Untreated seeds
can be stored up to 18 months without losing viability (Basu and Chakraverty
1986). Manual scarification, immersing the seeds in boiling water for one
minute, or treatment with sulfuric acid has shown to significantly increase
germination percentage. Following treatment, seed can be directly sown in the
field or in a nursery. Germination occurs within 7-10 days with young seedlings
obtaining a height of 8-15 cm in approximately three months. Seedling maturity
occurs two to three months later at 20-30 cm in height. Nursery stock
transplants well.
Growth is initially slow, but increase rapidly after the first
year. Following the first year of establishment, average annual growth rates of
2.3-2.6 cm in diameter and 2.0-2.3 m height have been recorded in American Samoa
(Adkins 1994). Trees planted 1 x 2 m apart for windbreaks, and at a spacing of 2
x 2 m in plantations can be thinned in three to five years to provide fuelwood
and construction materials. As a shade tree, spacing varies from 5-10 m
depending on the companion crop and site. The trees resprout easily allowing for
coppice management with good survival.
Despite an inability to suppress weeds, the seedlings are rather
hardy and can survive with minimal maintenance. Adenanthera pavonina is
compatible with most tropical field and tree crops, allowing for their usage in
integrated production systems.
Symbioses
Although Allen and Allen (1981) indicate the inability of A.
pavonina to nodulate, this legume is generally considered to be nitrogen-fixing.
Sparse, fast growing, brown nodules with isolates confirmed to be Rhizobium have
been observed by Lim and Ng (1977). The author observed root nodules, both in
old nursery stock and in the field, during research conducted in American Samoa.
Norani (1983) confirmed the presence of VA mycorrhiza on the roots of nursery
stock.
Limitations
Despite its susceptibility to crown damage in high winds, the
ability to recover is remarkable. No insect or disease problems have been
reported.
Research
Additional investigation concerning the nitrogen-fixing ability
on native and naturalized populations is required. Continued research on
fuelwood production and fodder usage is necessary.
References
Adkins, R v-C. 1994. The role of agroforestry in the
sustainability of South Pacific Islands Species Trials in American Samoa. MS.
Thesis, Utah State University. Logan, Utah 133 p.
Allen, O.N. and E.K Allen 1981. The Leguminosae: a source book
of characteristics, uses, and nodulation. University of WisconsinPress. Madison,
Wisconsin. 812 p.
Balogun, A M. and B.L. Fetuga. 1985. Fatty acid composition of
seed oils of some members of the Leguminosae Family. Food Chemistry, 17(3):
175-82.
Basu, D. and R.K. Chakraverty. 1986. Dormancy, viability and
germination of Adenanthera pavonina seeds. Acta Botanica Indica, 14 (1): 68-72.
Benthall, A P. 1946. Trees of Calcutta and its neighborhood.
Thacker Spink and Co. Calcutta. 513 p.
Burkill, I.H. 1966. A dictionary of the economic products of the
Malay peninsula, 2 ea., Volume 1, A-H Government of Malaysia and Singapore.
Kuala Lumpur, Malaysia. 1240 p.
Clark, W.C. and R.R.Thaman (eds). 1993. Agroforestry in the
Pacific Islands: Systems for sustainability. United Nations University Press.
Tokyo, Japan. 279 p.
Lim, G. and H.L.. Ng. 1977. Root nodules of some tropical
legumes in Singapore. Plant and Soil, 46: 317-27.
Little, E.L. Jr. and F.H. Wadsworth. 1964. Common trees of
Puerto Rico and the Virgin Islands. Agriculture Handbook No. 249. USDA Forest
Service. Washington, D.C. 14446 p.
Norani, A. 1983. A preliminary survey on modulation and VA
mycorrhiza in legume roots. Malaysian Forester, 46: 171-74.
Rajaguru, A S.B. 1990. Availability and use of shrubs and tree
fodders in Sri Lanka In: Devendra, C. (ed). Shrubs and tree fodders for farm
animals. International Development Research Centre. Ottawa, Ontario, Canada pp:
237-43.
Watt, J.M. and M.G. Breyer-Brandwijk. 1962. The medicinal and
poisonous plants of southern and eastern Africa, 2 ed. E &; S
FACT 96-03 June
1996
