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Useful Tropical Plants

Acacia mearnsii

De Wild.

Fabaceae


Classification of the genus Acacia (in the wider sense) has been subject to considerable debate. It is generally agreed that there are valid reasons for breaking it up into several distinct genera, but disagreement in the way this should be done. Some authorities have wanted to transfer this species to the genus Racosperma, but the latest decision (in 2011 and still not fully accepted) is that it remains in Acacia[
K
Title
Plants for a Future
Author
Ken Fern
Description
Notes from observations, tasting etc at Plants For A Future and on field trips.
].

+ Synonyms

Acacia molllissima Willd.

Racosperma mearnsii (De Wild.) Pedley

Common Name: Black Wattle

Acacia mearnsii
Flowering tree growing in an open position
Photograph by: Fagg, M.
Image credit to Australian National Botanic Gardens
Acacia mearnsii Acacia mearnsii Acacia mearnsii Acacia mearnsii Acacia mearnsii

General Information

Black wattle is a small to large, spine-free, evergreen, single-stemmed or multi-branched tree with a low, rounded, spreading crown[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. It grows from 6 - 25 metres tall, usually with a straight bole that can be up to 50 cm in diameter[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].
This species is the world's premier source of tannins and it is widely cultivated in warm temperate to tropical areas for its wood and tannins[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].

Known Hazards

None known

Botanical References


Range

Australia - New South Wales, Victoria, South Australia, Tasmania.

Habitat

An understorey tree of tall open forests, in fringes of closed forests or in dense thickets on recolonized lands[
310
Title
Plant Resources of Southeast Asia
Publication
 
Author
 
Website
http://proseanet.org/
Publisher
 
Year
0
ISBN
 
Description
Lots of information on the uses of the plants of SE Asia.
].

Properties

Weed PotentialYes
Medicinal Rating *  *
Other Uses Rating *  *  *  *
HabitEvergreen Tree
Height15.00 m
PollinatorsBees, Insects, Self
Self-fertileYes
Cultivation StatusCultivated, Wild

Cultivation Details

A plant of warm temperate to subtropical areas, it can also be grown at moderate to high elevations in the tropics. It is found at elevations from 300 - 2,440 metres in areas where the mean annual temperature is in the range 9 - 20°c and the mean annual rainfall is 500 - 2,050 mm[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. It prefers a moderate climate, exhibiting great intolerance to extreme heat or cold[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. Its lower altitudinal range is decided by the fact that trees cannot stand high summer temperatures, and the upper altitudinal limit is based on the fact that the tree does not tolerate temperatures below 0°c[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. Winter frosts and cold winds during the early part of the rainy season affect growth and survival rate, but older trees can withstand mild frost[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. Localities experiencing severe hailstorms and snowfall are unsuitable[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].
Flourishes in deep, well drained, light textured and moist soils[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. It thrives in well-aerated, neutral to acid soils, loamy soils, soils derived from shale or slate and is highly intolerant of alkaline and calcareous soils[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. Soils with lateritic pan close to the surface are most unsuitable[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. Adequate soil moisture is a prerequisite for satisfactory growth[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. Trees cannot withstand drought because of their superficial root system and high rate of transpiration[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].
In Hawaii, A. Mearnsii is a noxious weed and spreads prolifically at elevations between 600 - 1,200 metres in the 1,000 - 1,200 mm rainfall zones[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. The plant is also showing signs of being invasive in other areas, helped particularly by its prolific seed production and the long viability of the seeds in the soil[
413
Title
Global Invasive Species Database
Publication
 
Author
 
Website
http://www.issg.org/database/welcome/
Publisher
 
Year
0
ISBN
 
Description
Very detailed information on almost 400 species (with more being added) of plants that have become weeds in areas outside their native range.
].
Trees begin to yield fertile seed from the age of 5 years, giving good annual crops[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].
The tree regenerates naturally from seed after burning in clear-felled plantations[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. Seed may lie dormant in the soil for up to 6 years without loss of viability[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].
The trees have strong light requirements and respond to thinning in the early years. Growth rate is comparatively slow for the first 1 or 2 years. Thereafter, both height and diameter increments are rapid up to the age of 6 - 7 years, after which they fall off gradually[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].
The tree has low coppicing power[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].
Taproot development largely depends upon the depth of the soil, but the tree has the general tendency to develop a superficial lateral root system. Because of this, trees are liable to being uprooted by strong gales during the monsoon season[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[
200
Title
The New RHS Dictionary of Gardening. 1992.
Publication
 
Author
Huxley. A.
Publisher
MacMillan Press
Year
1992
ISBN
0-333-47494-5
Description
Excellent and very comprehensive, though it contains a number of silly mistakes. Readable yet also very detailed.
].

Edible Uses

None known

Medicinal

The bark is rich in tannins and so can be used in the many ways that astringents can be employed such as to treat diarrhoea and dysentery, to treat haemorrhoids, stop internal bleeding, bathe cuts and abrasions, as a mouthwash to tighten the teeth in the gums etc[
413
Title
Global Invasive Species Database
Publication
 
Author
 
Website
http://www.issg.org/database/welcome/
Publisher
 
Year
0
ISBN
 
Description
Very detailed information on almost 400 species (with more being added) of plants that have become weeds in areas outside their native range.
].

Agroforestry Uses:

It grows well at high elevations, even on slopes with shallow or poor acid soils that are unstable and will not support agricultural crops[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. It can, therefore, be very effective in preventing soil erosion. Densely packed plantations have proved effective in preventing further erosion, even on hillsides of up to 50 degrees slope[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].
The tree has been planted as a shelterbelt, a firebelt and as a shade tree in plantations[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].
An efficient nitrogen-fixer and good source of green manure, it thus can restore and regenerate soils[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].

Other Uses

Wattle bark is the most widely used tannin material in the world[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. It contains 30 - 45% (dry basis) high-quality tannins[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. A powdered bark extract is also used to prepare tannin formaldehyde adhesives for exterior grade plywood, particleboard and laminated timber[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. Possibilities of using the bark in the production of biodegradable polyurethane foam are being tested[
299
Title
Protabase - Plant Resources of Tropical Africa.
Publication
 
Author
 
Website
http://www.prota.org
Publisher
 
Year
0
ISBN
 
Description
An excellent on-line database with detailed information on over 3,200 species of useful plants of Africa.
].

The heartwood is pale brown with a pinkish tinge; it is not sharply demarcated from the sapwood. The texture is moderately fine and uniform; the grain commonly interlocked; lustre is medium; there is no distinctive odour or taste.The wood is moderately hard to hard, heavy, fairly tough and strong, not very durable. It dries rapidly, but with pronounced warp, particularly cupping; shakes tend to open and knots to split slightly. It is moderately easy to work and polishes well. It is used for house poles, mine props, tool handles, cabinet work, joinery, flooring, construction timber and matchwood[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
,
316
Title
Tropical Timbers of the World. Ag. Handbook No. 607.
Publication
 
Author
Chudnoff. Martin.
Publisher
USDA Forest Service. Wisconsin.
Year
1984
ISBN
 
Description
Terse details on the properties of the wood of almost 400 species of trees from the Tropics.
].
The pulp productivity is about 320 kg/cubic metre[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. Testing has shown that it yields a pulp with good strength characteristics and is suitable for wrapping paper and hardboard. It is also used for rayon[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].
Originally distributed as a source of tannin, black wattle is now recognized as a valuable fuel wood[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. The wood is moderately dense with specific gravity about 0.75, splits easily and burns well with a calorific value of 3,500 - 4,600 kcal/kg. The charcoal is extensively used in Brazil and Kenya, and in Indonesia the tree is extensively used as a domestic fuel and for curing tobacco[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].

Propagation

Seed - requires pre-treatment. This can be carried out by abrading the hard seed coat to allow the ingress of water[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. A more common method is to soak the seed in warm or hot water prior to sowing. There are various different variations, one common method is to pour a small amount of almost boiling water over the seeds - this cools quickly so does not kill the seed. The seeds are then left in warm water for 12 - 24 hours prior to sowing[
K
Title
Plants for a Future
Author
Ken Fern
Description
Notes from observations, tasting etc at Plants For A Future and on field trips.
]. A germination rate of 75% occurs in 7-15 days[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. The sown seeds are covered with bracken fronds to protect the beds from excessive evaporation and runoff during watering. The bracken cover is removed after germination[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
]. Seedlings are pricked out when they are 5 - 6 cm tall with 3 or 4 pairs of leaves, planted into polythene bags 13 x 8 cm, and watered daily until out-planting. It is essential to shift the seedlings frequently to prevent them from striking roots in the ground. The seedlings should be about 9 months old at the time of planting[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].
Seeds stored in airtight containers at room temperature maintain their viability for several years[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].
Vegetative propagation by rooted cuttings is difficult[
303
Title
World Agroforesty Centre
Publication
 
Author
 
Website
http://www.worldagroforestry.org/
Publisher
 
Year
0
ISBN
 
Description
An excellent online database of a huge range of trees giving very good information on each plant - its uses, ecology, identity, propagation, pests etc.
].

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