Common Name: Common Ru

General Information

Casuarina equisetifolia is an evergreen tree with a finely branched, feathery crown, usually growing growing from 6 - 35 metres tall though occasional plants up to 60 metres tall have been recorded. The straight, cylindrical bole can be free of branches for 10 metres or more and 20 - 100cm in diameter; occasionally with buttresses[, ].
Of considerable importance for agroforestry, the tree is widely planted throughout the tropics, especially for being able to provide timber whilst growing on poor sandy soils near the coast and thus also providing shelter and protection for the soil[, ]. The tree is also commonly grown as an ornamental, especially near the sea where it can also offer shelter from the wind[].

Known Hazards

None known

Botanical References

Range

E. Asia - Bangladesh, Myanmar, Thailand, Vietnam, Malaysia, Indonesia, Philippines, Australia and the Pacific Islands.

Habitat

Confined to a narrow strip adjacent to sandy coasts, rarely extending inland to lower hills. Found on sand dunes, in sands alongside estuaries and behind fore-dunes and gentle slopes near the sea[].

Properties

Weed Potential	Yes
Medicinal Rating
Other Uses Rating
Habit	Evergreen Tree
Height	30.00 m
Growth Rate	Fast
Pollinators	Wind
Self-fertile	No
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Casuarina equisetifolia is adaptable to a wide range of conditions, being found from the semi-arid to subhumid tropics and subtropics, usually near sea level but succeeding under cultivation at heights up to 1,400 metres[, ]. It grows best in areas where the mean annual temperature is in the range 10 - 35°c and prefers a mean annual rainfall in the range 700 - 2,000mm, though it tolerates 200 - 3,500mm[, ]. In most areas where it grows there is a distinct dry period of 4 - 6 months, although this seasonality decreases towards the equator in Southeast Asia and in the southern parts of its range in Australia[].
Requires a sunny position and a well-drained soil[, ]. Prefers alkaline to neutral soils[]. Prefers a pH in the range 5 - 6.5, but tolerates 4 - 8.5[]. Plants are very resistant to salt spray and can also tolerate occasional inundation by sea water at extremely high tides[]. Young plants are susceptible to drought until their roots reach the groundwater table, which may take up to 2 - 3 years after planting[], but then they become very drought resistant[].
Casuarina equisetifolia is a fast growing species with prolific seeding ability which is able to take advantage of disturbed sites for colonization. Where it establishes it may form dense, low biodiversity stands with negative impacts on native flora, fauna, soil character and dynamics. It is reported to be invasive in a number of countries and is a particular problem in Florida and South Africa, and is said to be invasive in many other countries including Brazil and the Caribbean[].
This species can flower and produce fruit all year round[].
Common ru has a life span of 40 - 50 years and displays fast early growth. Under favourable conditions, early growth rates are about 2 metres per year. On favourable sites, it can yield an annual increment of 15 cubic metres per hectare of wood in 10 years[].
In South China, where an estimated 1 million hectares in shelterbelts along the coastal dunes have been established since 1954, heights of 7 - 8 metres and diameters of 5 - 7 cm are achieved in about 4 years[].
The rotation period ranges from 4 - 5 years for fuel wood and 10 - 15 years for poles[].
Common ru can be the only woody species growing over a ground cover of dune grasses and salt-tolerant broadleaved herbs; it can also be part of a richer association of trees and shrubs collectively termed the Indo-Pacific strand flora[].
The tree is not fire resistant and protection is necessary[].
The plant coppices only to a limited extent and best results are obtained when cut young[].
Timely thinning is essential as Casuarina species trees demand light[].
Young trees are susceptible to competition from weeds, especially grasses[].
Although the tree is evergreen, it usually sheds a large amount of twigs throughout the year[].
In Asia, leaf litter from plantations is often removed for use as fuel and this draws heavily upon soil phosphorus and potassium reserves. This can result in reduced yield in the subsequent rotation[].
In cultivation, this species hybridizes with Casuarina glauca and Casuarina junghuhniana[].
Root nodules containing the actinorhizal symbiont Frankia enable Casuarina equisetifolia to fix atmospheric nitrogen. These root nodules can be prolific[].
The tree possesses proteoid roots and forms associations with vesicular arbuscular mycorrhizae[].
This species can be monoecious or dioecious. Dioecious plants will require both male and female forms to be grown if fruit and seed are required[, , ].

Edible Uses

None known

Medicinal

Root extracts are used for the treatment of dysentery, diarrhoea and stomach-ache[].

A decoction of the twigs is used for treating swelling[].

The fresh bark is an excellent astringent[]. It is used in the treatment of chronic diarrhoea and dysentery[, ]. A decoction of the inner bark, combined with the inner bark of Terminalia catappa, is taken as a treatment for asthma and shortness of breath[].
The powdered bark is used for treating pimples on the face[].

The cambium layer beneath the bark is squeezed and used to sedate a mentally ill or aggressive patient[].

Agroforestry Uses:

With its fast rate of growth, ability to fix atmospheric nitrogen and to grow in distured and poor soils, common ru is an excellent plant for use in soil stabilization projects. Since it is salt tolerant and succeeds in sand, it is particularly suited for controlling erosion along coastlines, estuaries, riverbanks and waterways. In Sarawak, Indonesia, for example, the species is protected because of its importance in controlling coastal erosion[]. Its ability to become naturalized in some of the areas where it has been introduced, however, means that it should not be introduced into new areas without a proper risk-assessment.
Many areas where the species naturally occurs are susceptible to tropical cyclones or typhoons, and its general tolerance to strong winds has encouraged its use in protective planting[]. The abundance of highly branched twigs absorbs wind energy amazingly well[]. In areas with hot, dry winds the tree protects crops and animals herds[]. In South China, an estimated 1 million hectares has been established in shelterbelts along the coastal dunes[].
The tree fixes atmospheric nitrogen and is able to grow vigorously on barren, polluted sites and thrive in deep sandy soils[]. It is therefore often planted for reclaiming and improving the land.
It is remarkably suited for boundary planting as it does not intercept much of the incoming solar radiation and yields substantial quantities of green leaf manure on lopping as well as several other products[]. It is also amenable to trimming and so can be used as a hedge[].
With high productivity and properties that enhance soil fertility, it shows promise as an agroforestry species for arid and semi-arid areas. Experiments at Prabhunagar, India, for example, showed that citrus trees grew larger under this plant than in pure stands[].

Other Uses

The bark contains 6 - 18% tannin[]. This is used for preserving ropes etc, and also contains a red pigment, so can be used as a dye[, ].

The ashes from the burnt wood are a rich source of alkali, which is sometimes used to produce a coarse soap[].

The tree yields a heavy hardwood with an air-density of 900-1000 kg/cubic m. The heartwood is pale red, pale brown to dark red-brown, moderately to sharply differentiated from the sapwood, which is yellowish or pale yellow-brown with a pink tinge. The grain is coarse, straight, slightly interlocked or wavy; texture fine to moderately fine and even. Shrinkage is moderate to very high, and in the latter case the wood is difficult to season due to severe warping and checking. Wood is hard to very hard and strong. The heartwood is highly resistant to pressure treatment, but sapwood is amenable to such treatment. Heartwood is also resistant to dry-wood termites. The wood is used for house posts, rafters,shingles, electric poles, tool handles, oars, wagon wheels and mine props[].
The wood is used to produce paper pulp using neutral sulphate and semi-chemical processes, and as a raw material for rayon fibres[].
The highly regarded wood ignites readily even when green, and ashes retain heat for long periods[] It has been called ‘the best firewood in the world’ and also produces high-quality charcoal. Calorific value of the wood is 5,000 kcal/kg and that of the charcoal exceeds 7,000 kcal/kg. It has been used for both domestic and industrial fuel such as for railroad locomotives[]. In Asia, leaf litter from plantations is often removed to be used as fuel[].

Propagation

Seeds can be sown without pre-treatment but should be protected from ants[]. Germination takes up to 2 weeks and is epigeal. Seedlings should be planted in well-drained light soils, not clay soils, to decrease the incidence of diseases and pests. Appropriate watering, correct spacing of plants and adequate light should check damping-off in the nursery. Seedlings can be pricked out when 3 - 10 cm tall and transferred to beds or containers. Plants are typically suitable for out-planting when 25 - 30 cm tall[].
Storage behaviour is orthodox. Viability can be maintained for several years in hermetic storage at 3 deg. C with 5-9% mc. There are about 26000 seeds/kg but viability is often low, even for fresh seed, averaging 50%
Cuttings are made from small branchlets 2 mm diameter and 10 - 15 cm length, and rooting is enhanced through the use of rooting hormone[].
Air-layering is sometimes practised but is too costly for large-scale operations[].

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