Because of their proven performance, Casuarina cunninghamiana, Casuarina equisetifolia, Casuarina glauca, Casuarina junghuhniana, and Casuarina oligodon are each described in more detail in this chapter. Lesserknown species with promise are discussed in chapter 7.
Botanic Name Casuarina cunninghamiana Miq.
Common Names River sheoak, creek oak, river oak, casuarina
Main Attributes The tree is one of the largest of the casuarinas. Handsome of appearance, it can be used for ornamental planting as well as for shade and shelter. It is a good street tree and is suitable for semiarid regions. It provides heavy shade and is almost trouble free. It has some cold tolerance, is very adaptable, and withstands periodic inundation so that its major use in Australia is for protecting stream banks from erosion. Because of its importance for this purpose, in New South Wales it may not be felled without a permit.
Description Casuarina cunninghamiana grows up to 40 m in height and more than 1 m in diameter. Its thin deciduous branchlets are soft and short and carry whorls of 6-8 leaf-teeth.
Distribution Native to eastern and northern Australia, it is found growing from the south of New South Wales (latitude 37°S) to the north of Queensland (latitude 12°S). Typically, it occurs fringing freshwater streams and rivers on both sides of the Great Dividing Range. A distinct race, possibly a separate species, is found along the larger rivers in the higher rainfall areas of the Northern Territory.
Casuarina cunninghamiana is extensively planted in Argentina and neighboring countries for windbreaks and to protect stream banks. It is also established in Florida. In Egypt it is important for shelterbelts. In Israel it is widely planted along railroads and highways for windbreaks and woodlots. And in Bulawayo, Zimbabwe, it is planted as a street tree.
· Temperature. Adapted to climates varying from temperate
to tropical. The climatic range in its native habitat varies from warm subhumid
to warm semiarid. The species is able to tolerate up to 50 light frosts per year
- such incidences occurring mainly in the southern parts of
· Altitude. Sea level to about 800 m.
· Rainfall. From 500 to 5,000 mm per year, but, as the tree is riverine, rainfall alone is no indication of the total moisture available. The incidence of the principal rainfall varies from a weak summerautumn maximum in southern New South Wales to a strongly defined summer maximum (monsoonal) in the north.
· Soil. Soils are usually alluvial and vary from silty loams to sands to gravels. In Hawaii it grows well on histosols developed over acidic lava (pH 5.0).
Root Suckering Occurs, definitely in eastern Australia.
Limitations Not as salt tolerant as the closely related Casuarina glauca. On highly calcareous soils it is likely to turn chlorotic. Seedlings are susceptible to browsing damage and need protection from grazing in the early years.
Botanic Name Casuarina equisetifolia Forst. & Forst.
Synonym Casuarina litorea L.
Common Names Casuarina, sheoak, horsetail oak, Australian pine, ironwood, whistling pine, agoho (Philippines), ru (Malaysia), filao (Senegal), nokonoko (Fiji)
Main Attributes This is a large and usually long-lived tree and has the widest distribution both natural and planted of all the casuarinas. It has proved itself in scores of tropical countries. It is particularly valuable for stabilizing sand dunes, as it withstands salt spray, tolerates infertile soils, and is drought tolerant. Most of the experiences described in chapter 2 are with this species.
This is a species for warm to hot subtropical and tropical climates. Although it is not frost hardy, it tolerates a wide range of temperatures. The calorific value of its charcoal, 7,181 kcal per kg, is among the highest of any firewood species. The trees grow fast, sometimes reaching heights of 3 m within 8 months of transplanting to the field.
Description Two subspecies are recognized, Subspecies incana is a small tree that could be useful for low-growing shelterbelts but that has been little tried as an exotic. Subspecies equisetifolia has a tall stem and narrow crown. Unless otherwise stated, any reference to Casuarina equisetifolia in this book refers to this subspecies.
Distribution Subspecies incana occurs only along the coast of Queensland and northern New South Wales. The natural distribution of subspecies equisetifolia extends along seacoasts from Malaysia to subtropical Australia, Melanesia, Micronesia, the Philippines, and Polynesia.
· Temperature. In Australia these trees occur in the hot
humid climatic zone, but they extend into the hot subhumid zone (while
subspecies incana has its main distribution in the warm subhumid zone). Frosts
are absent in most of its habitats, although in the south there may be 1-3
frosts a year.
· Altitude. This is generally a lowland tree but is grown up to about 600 m elevation in Hawaii.
· Rainfall. In its natural habitat, annual rainfall is from 700 to 2,000 mm, often with a dry season of 6-8 months. However, it has been planted successfully in areas with annual rainfall as little as 200-300 mm or as much as 5,000 mm.
· Soil. The species tolerates calcareous and slightly saline soils. Reportedly it grows poorly on fine-textured soils but it grows well on clays in Hawaii. It can withstand partial waterlogging for a time.
Root Suckering Occurs.
Limitations Initially, the trees have poor ability to compete with weeds, especially in dense grass cover. Seedlings are vulnerable to attack by ants, crickets, and other insect pests. The trees are susceptible to root rot. Casuarina equisetifolia can exhaust the moisture in the soil, lower the water table of the site, and restrict growth of a healthy understory. The tree is fire sensitive and can be browsed only lightly without being damaged. Although other Casuarina species coppice readily, Casuarina equisetifolia coppices only to a limited extent and only when cut young (3-4 years).
Botanic Name Casuarina glauca Sieb. ex Spreng.
Common Names Swamp sheoak
Main Attributes This tall tree can survive on difficult sites where other trees fail because of salinity, waterlogging, or shallow water table. It withstands even periodic tidal inundation.
Sometimes it occurs where it gets drenched in salt spray from the sea. In Egypt it has proved more drought tolerant than Casuarina cunninghamiana and Casuarina equisetifolia.
In Israel it outperforms all the other casuarinas, reaching 20 m after 12-14 years, even on saline water tables.
It is favored for shelter purposes. Its canopy tends to commence at ground level, owing to low branching or the development of root suckers, which arise spontaneously around the parent tree.
Description This is an erect, fast-growing tree, typically 10-14 m tall, although in favorable localities it may reach 30 m. The main stem, which may be buttressed and fluted, is moderately straight and typically dominant for most of the tree's height. Free-growing specimens have a somewhat sparse and narrow crown. The slender deciduous branchlets (about 1 mm in diameter) carry 12-20 small leaf-teeth in widely spaced whorls. They are much coarser (and a little longer) than those of Casuarina equisetifolia or Casuarina cunninghamiana.
Distribution Casuarina glauca is found in a narrow belt hugging the coast of eastern Australia from Bega in New South Wales to Rockhampton in Queensland. It has also been successful in the marshes and saline soils of Israel, Cyprus, India, Kenya, Malawi, South Africa, Egypt, and Florida.
This casuarina is most common along the edges of swampy flats near estuaries and along tidal reaches of rivers. It is also sometimes found on or near beach fronts. The flats may be only marginally above tidal limits; the water table is usually close to the surface (often within 30 cm of the surface).
· Temperature. 5°-33°C.
· Altitude. Sea level to 900 m (in Hawaii).
· Rainfall. 500-4,000 mm (in Hawaii).
· Soil. In its native habitat soils are often sandy or clayish and are underlain with rock. Salt content is often high. However, the trees occasionally occur on moist, rocky headlands.
In Israel the tree grows on very dry sites in the Negev Desert. It has grown where a layer of salt covers the soil surface (50,000 ppm).
Although most natural stands are on acidic soils, Casuarina glauca has shown good growth on alkaline clay-loam soils with shallow water tables in hot semiarid areas of Central Australia. In Thailand the seedlings have tolerated high levels of calcium in the soil and as much as 30 percent limestone. In southern Florida it flourishes on oolitic limestone. In Hawaii it is frequently planted on much-weathered parent basalt in eroded blowouts, sometimes in holes blasted by dynamite. It is also planted in pure limestone sand and does well.
Nodulation Prolific. The tree sometimes produces huge growths from which root suckers later arise.
Root Suckering Even without root damage it forms thickets of suckers. Suckering is increased by pruning the trees.
Limitations Suckers are grazed by livestock, but they have
little value as forage. Because it regenerates vigorously from root sprouts,
this species is a possible weed and, as already noted, is a pest in parts of
Florida and is regarded as noxious in Hawaii.
In Hawaii it does not attain the height of Casuarina cunninghamiana or Casuarina equisetifolia, probably because it stagnates from abundant suckering.
Botanic Name Casuarina junghuhniana Miq.
Synonym Casuarina montana Jungh.
Common Name Jemara (Indonesia)
Main Attributes This tall, straight casuarina has good form for
a plantation species. It is adapted to hot, humid conditions, to monsoonal
climates with a long dry period, and to highland areas in the tropics. It grows
quickly in compact clay soils near Bangkok, Thailand.
It has some salinity tolerance and thrives on many types of soil. It reportedly competes well with vigorous tropical weeds such as lmperata cylindrica. So far, it is widely used only in Thailand. There the trees do not produce seed and are reproduced artificially using vegetative methods.
Description This is a long-lived pioneer tree that grows to majestic size - 35 m in height and l m in diameter. The branchlets are graygreen to dark green and carried in a narrow conical crown.
Distribution Casuarina junghuhniana is native to highland
regions of eastern Indonesia - to East Java, Bali, and the Lesser Sunda group of
islands. There it occurs in extensive pure stands on mountain summits. It
pioneers the natural revegetation of deforested grassland, volcanic ash and
sand, gravelly stream beds, and screes. Man-made grassland has allowed it to
extend its area manyfold, at the cost of mixed mountain forest and scrub forest
that formerly prevailed.
A hybrid of Casuarina junghuhniana and Casuarina equisetifolia was introduced to Thailand around 1900. Today, its good, straight stems and symmetric conical crown make it a popular ornamental and cultivated crop throughout the country.
· Temperature. Unknown.
· Altitude. Its natural distribution is up to 3,000 m. In Thailand and South India, however, it is mostly grown near sea level.
· Rainfall. In its native habitat the rainfall pattern is monsoonal with a well-defined summer maximum and a range from 700 to 1,500 mm. The tree is moderately drought tolerant. (In 1951 the hybrid was introduced into South India from Thailand. In 1972 a severe drought killed all 6-year-old Casuarina equisetifolia trees, but not the C. junghuhniana x C. equisetifolia hybrid.)
· Soil. It can grow well in various types of soil, from compact clay to light volcanic soil.
Nodulation Nodules have been found on a tree in the Bandung region of Indonesia.
Root Suckering The root system extends laterally and produces abundant root suckers.
Limitations In Thailand and India the hybrid trees do not produce seed and are propagated only by vegetative means, usually by airlayering, using the abundant suckers or branches.
Botanic Name Casuarina oligodon L. Johnson
Common Names Yar or soft yar (Papua New Guinea), sheoak
Main Attributes The Papua New Guinea government is encouraging local people to grow Casuarina oligodon as firewood in the Highlands. The Office of Forests in the Highland provinces distributes seedlings, which are planted by local landowners. The trees are highly self-regenerating, and they help in reforesting grasslands. The wood is used in construction, but because it is durable, it is also suitable for fences. Its main use is for fuelwood in the
Highlands where nights are cool. It is also used for windbreaks, and most villages have Casuarina oligodon planted around their boundaries. The tree grows well even with competition from vigorous grasses (such as Imperata cylindrica, Saccharum robustum, and Themeda australis). Coffee is a major cash crop in the Papua New Guinea Highlands, and
Casuarina oligodon is useful on coffee plantations because it shades the coffee bushes and improves the soil by fixing nitrogen.
Description This is a medium to tall tree, reaching 30 m in height and 0.6 m in diameter. The bark is gray-brown and fissured, peeling off in irregular flakes. The tree produces small cones (diameter less than 1 cm).
Distribution The species is native to New Guinea and is found mostly in upland valleys. It forms extensive pure stands along river beds, but at times it is associated with Casuarina papuana (see page 94). It occurs commonly on stream banks and ridge tops and on abandoned garden and village sites. In the Papua New Guinea Highlands, people fallow the land 10-20 years under Casuarina oligodon. It is part of their traditional land-use pattern.
This species is little known outside New Guinea, but in Hawaii it has grown very rapidly.
· Temperature. This is truly a tropical highland
· Altitude. The tree is found up to 2,500 m or higher in Papua New Guinea.
· Rainfall. It occurs naturally in areas where the rainfall ranges from 1,900 mm to 2,600 mm and humidity is high throughout the year. In Hawaii it is planted in an area with 5,000 mm rainfall but good drainage.
· Soil. It is mostly found in sandy soils along creeks and rivers but grows well in colluvial soils, humic brown-clay soils, and alluvial and meadow soils.
Root Suckering The species mainly spreads through seed and generally does not spread through suckers. However, it has been known to form epicormic shoots after fire or when damaged by other natural causes.
Limitations Casuarina oligodon may not grow successfully on poor soils. It seems to be very sensitive to areas of high salt concentrations. It has also proved susceptible to wind breakage in Hawaii; it appears to be much more brittle than any of the other species.