|Casuarinas: Nitrogen-Fixing Trees for Adverse Sites (BOSTID, 1984, 114 p.)|
In addition to the five species described in chapter 6, there are several lesser-known casuarinas that have real or potential value. As more introductions are attempted and more is learned about them, they could make an important place for themselves. None has yet been tested significantly outside its native habitat.
The following pages describe:
Botanic Name Casuarina campestris Miq.
Synonym Allocasuarina campestris (Miq.) L. Johnson
Main Attributes This species provides perhaps the ultimate in wind protection. Single rows with plants 2-3 m apart provide excellent shelter for livestock and dwellings. Casuarina campestris protects soil well and is planted for conservation purposes. It is now used mainly for low, hedge-type shelterbelts. It will grow on a wide range of soils, including coastal sands.
Description Although it may also grow as an erect tree with a dense crown, this species is usually a very bushy, multistemmed shrub only 1-3 m high.
Distribution Casuarina campestris is native to the southwestern part of Western Australia.
· Temperature. This species is native to temperate areas of
Western Australia. Throughout most of its range it receives 1-12 frosts per
· Altitude. It occurs from near sea level to about 375 m.
· Rainfall. It is found mainly in the semiarid climatic zone, but it also extends into both subhumid and arid zones. The 50th percentile rainfall is 225-400 mm, and the lowest precipitation on record in the area is 140-250 mm. There is a clearly defined winter maximum.
· Soil. Casuarina campestris has been recorded on some extremely poor soils such as those derived from cemented laterite, greenstone, ferric-conglomerate, broken quartzite, and limestone. It has been also recorded on loams, shallow clays over laterite, and coarse gravelly soils.
Root Suckering Unreported.
Limitations The wood is available only in small diameters. Its technical properties are unknown.
Botanic Name Casuarina cristata Miq. There are two subspecies: Casuarina cristata subspecies cristata and Casuarina cristata subspecies pauper.
Synonyms Casuarina lepidophloia F. Muell.; Casuarina glauca Benth., in part; not Sieb.
Common Names Black sheoak, belah
Main Attributes This tree is valued as a source of light shade and shelter on farms, for timber, and, to a limited extend, as an emergency drought fodder.
Subspecies pauper is more suited to drier (as low as 250 mm
annual rainfall) and harsher conditions than subspecies cristata, as well as to
areas where there is limestone in the soil.
It also appears suitable for saline soils.
Subspecies cristata seems to require a rainfall greater than 400 mm. It is an excellent tree for windbreaks and is an attractive ornamental. Specimens growing in the open develop a dense crown, almost to ground level.
Description This smallish tree reaches a height of 20 m. It is erect in form, and when trees are planted close together the main stem is straight for more than half the total height.
Distribution Subspecies cristata is native to eastern Australia. It grows in a belt on the inland side of the Great Dividing Range in New South Wales and southern Queensland.
Subspecies pauper is native to a wide belt from western New South Wales across the central latitudes of South Australia to Western Australia.
· Temperature. Subspecies pauper occurs in an arid region
with burning hot summers and a few winter frosts.
· Altitude. The tree is found mainly below 350 m.
· Rainfall. Subspecies pauper grows where annual rainfall is very erratic, as low as 175 mm, and where there is a potential annual evaporation of 2,500 mm or more. In this region of low, open woodland or shrub steppe, this casuarina is often the only tree to be seen.
· Soil. This species seems to withstand compact clay soils and high alkalinity - pH 8.8 and lime content up to 3.5 percent calcium in the surface soil, for example.
Nodulation Good at most sites. In dry inland areas nodules are more difficult to locate as they are generally found deeper in the soil.
Root Suckering It reproduces readily by root suckers, often
forming large, dense stands of one sex, which could make it a pest in some
Limitations Young trees must be protected from grazing animals.
Botanic Name Casuarina decaisneana F. Muell.
Synonym Allocasuarina decaisneana (F. Muell.) L. Johnson
Common Name Desert sheoak
Main Attributes This is one of the remarkable trees of central Australia, the hottest and driest part of the continent. In parts of this area it may be the dominant tree of the landscape, occurring as scattered individuals or in groves. Frequently, it is the only tree species present in a landscape where even shrubs are not common.
Description This tree has a graceful pendulous habit when
mature, but the young plants are more upright. The trunk is straight and may be
more than half of the total height of 10-15 m.
The cones are ovoid and oblong and are 3-5.5 cm long and 2.5-3.5 cm thick.
Distribution It occurs mainly south and west of Alice Springs in the southern half of the Northern Territory and in adjacent areas of Western Australia and South Australia.
· Temperature. The trees withstand incredible conditions.
Mean maximum temperature of the hottest month is about 35°C, with readings
up to 47°C common. On the other hand, winter temperatures may fall to -
· Altitude. Within the range of 250-700 m.
· Rainfall. The mean annual rainfall value is 220 mm, based on 13 years of observation; in the lowest recorded year, only 38 mm of rain fell. The potential evaporation may exceed 3,000 mm a year.
· Soil. In its native habitat, Casuarina decaisneana grows on deep sandy soils and on undulating or low sites where the maximum seepage into the subsoil can be expected during the rare heavy rain.
Nodulation Nodules have been found on this species in the field, but they were not common at the sites examined.
Root Suckering Unreported.
Limitations The species has not been widely tested, and there is no knowledge of it under cultivation. It appears to be slower growing than other casuarinas. Some specimens, drip- irrigated at Alice Springs, reached 4 m in 6 years. The trees may have restricted soil requirements perhaps being intolerant of alkali.
Botanic Name Casuarina dielsiana C.A. Gardn.
Synonym Allocasuarina dielsiana (C.A. Gardn.) L. Johnson
Common Name Diels' sheoak
Main Attributes This small, compact tree provides good shelterbelt or shade trees when young (with age, the lower branches die). The Western Australian Forests Department recommends it for use in multirow shelterbelts. It merits trials for amenity planting or for the production of fuelwood and timber in areas with high summer temperatures, low and erratic rainfall, and rocky and freely draining soils.
Description The tree is commonly 5-8 m tall on moderately good sandy loams, but it is sometimes reduced to a bush only 4 m high on the top of dry gravelly ridges. The crown tends to be carried in the upper part of the trunk, while the lower parts are thinly branched.
Distribution It is a native of Western Australia, mainly within 300 km of the west coast and between latitudes 26°-30°S.
· Temperature. Summers are long and very hot, with the mean
maximum of the hottest month approaching 38°C.
· Altitude. Its habitat ranges in elevation from near sea level to about 300 m.
· Rainfall. Its native area averages 300-500 mm, with a well-defined winter maximum and only moderate variability.
· Soil. This species is typically found around or on the more rocky and rugged sites, and while it may edge sand plains, it is rarely found on them. The soils are mainly sand, sandy loams, or stony skeletal. Other soil types include gravels on ironstone ridges and light-red loams associated with granitic outcrops. Although it occurs naturally on welldrained, poor, and rocky soils, it is thought to have potential for compact clay soils in areas where the rainfall may be as low as 300 mm.
Root Suckering Unreported.
Botanic Name Casuarina fraseriana Miq. (formerly spelled C. fraserana)
Synonym Allocasuarina fraseriana (Miq.) L. Johnson Common Name Fraser's sheoak
Main Attributes This is a tall tree with promise for winter rainfall areas with nutrient-poor lateritic clays and sandy soils. In the southwest of Western Australia, one company is licensed to cut casuarinas and it utilizes only Casuarina fraseriana. Its products are wood turnery items (goblets, planters, saucers, bowls, and piano legs), roof shingles, and veneer for paneling. Reject logs are made into dowelling, moldings, and picture frames. Firewood is still cut from this species for the Perth market.
Description At its best this is an erect, somewhat pyramidal tree with a straight bole two- thirds of the tree height and an open crown. In particularly favorable areas it may reach heights of 14-15 m, but it is commonly only 9-12 m tall. Even on lateritic clay the height may be 10 m, but on poor sites such as dry sandy plains or rocky areas, the trees may be reduced to tall shrubs 2-5 m high.
Distribution This is a species of coastal southwestern Western Australia. It occurs mainly on a narrow belt on the seaward side of the ranges.
· Temperature. This is typically a species of warm humid
climates, but it extends slightly into the adjacent warm subhumid zone. Areas
immediately adjacent to the sea are frost free, while further inland, frosts may
average up to 11 per year.
· Altitude. From 50 m to about 500 m above sea level.
· Rainfall. The 50th percentile rainfall has a wide range, varying from 900 to 1,250 mm; in the lowest year on record, 500-750 mm of rainfall was recorded. There is a well-developed winter maximum rainfall.
· Soil. This casuarina is found on a wide range of soils, including deep, white, acid sands, oxisols, ultisols, and gravels, as well as yellow (iron stained) calcareous sands near Perth, Western Australia. It does not grow on the adjacent compact clay soils. It can handle nutrientpoor soils, but they must be well drained.
Nodulation Very variable; absent on some specimens, good on others.
Root Suckering Cut stumps produce vigorous new shoots and may be suitable for coppice management. Living trees are often burnt into hollow trunks in very hot wildfires; however, the trees recover, and new branches break out from beneath the very thick bark to form badly disfigured survivors.
Limitations Unreported. Actually, the species exhibits no features to suggest that it is invasive or would cause problems difficult to control.
Botanic Name Casuarina huegeliana Miq.
Synonym Allocasuarina huegeliana (Miq.) L. Johnson
Common Name Rock sheoak, granite sheoak
Main Attributes This is one of the largest casuarinas in the inland dry areas of Western Australia. The Forests Department of Western Australia considers that this species merits greater recognition for shade planting on poor, shallow sandy soils with low rainfall. The species also deserves consideration for ornamental planting on some difficult sites.
Description This tree is commonly only 5-12 m tall, although under favorable conditions it sometimes attains 14 m. In close stands the trees have a columnar habit, while open- growing specimens have a wide crown and a main stem that divides at one-fourth to one- third of plant height.
Distribution This casuarina is native to semiarid and subhumid areas in the southwest of Western Australia. Much of its occurrence is in the wheat belt.
· Temperature. In its native habitat summers are hot, with
mean maximum temperatures of the hottest month 29°-35°C, while mean
minimum temperatures of the coldest month are as low as 4°C. Areas near the
coast may be frost free, but inland there are 1-10 frosts a year.
· Altitude. It grows from just above sea level to 450 m.
· Rainfall. This is in the range of 300-750 mm. It is a winter rainfall zone with dry summers.
· Soil. The species derives its common names - rock sheoak and granite sheoak - from its occurrence on massive rocky outcrops (inselbergs). It is also found on sandy plains and on highly ferrugineous banded ironstone. It has been recorded on a wide range of other soil types: yellow clay-sands, sandy and gravelly loams, sandy clays, sandy types of all gradations, and oxisols and ultisols.
Nodulation It is difficult to obtain quantitative data because of problems excavating root systems at sites where this species grows.
Root Suckering Not known.
Limitations The tree is less suitable for shelterbelts, since the moderately dense crown is carried on the upper part of the stem, though it can be used in association with lower-story shrubs such as Casuarina campestris (page 68).
Botanic Name Casuarina littoralis Salisb.
Synonyms Casuarina suberosa, Allocasuarina littorals (Salisb.) L. Johnson
Common Name Black sheoak
Main Attributes Probably the most plentiful casuarina in Australia, this is mainly an understory species of tall open forests, but it occurs in woodland areas and in the more open patches of closed forest. It probably provides the neighboring trees with the nitrogen required for growth. This is a tree for relatively low, narrow shelterbelts and for use in avenues where larger trees are undesirable. It recolonizes sand blows and regenerates vigorously from seed drop after forest fires.
Description Casuarina littoralis is usually a small open tree or sometimes a large shrub in the height range of 3-12 m. In forest and shrubland associations this species has an erect habit and narrow crown, but on windswept coastal heaths it may be reduced to a procumbent plant.
Distribution This tree has the widest range of latitudes of any Australian casuarina. It is native to a belt (mainly within 100 km of the sea) from the northern tip of Queensland (latitude 12°S) to Tasmania (latitude 43°S).
· Temperature. The species is found in widely varying
climates. Most of the trees occur in warm subhumid and humid climates, but
appreciable stands are found in the cool subhumid zone and some in the hot humid
zone. At the highest altitudes in New South Wales the trees are subjected to as
many as 70 frosts a year.
· Altitude. While most plentiful at altitudes under 300 m, the tree is found at elevations up to 1,200 m.
· Rainfall. The 50th percentile rainfall is 650-1,250 mm and the lowest on record is 300-500 mm. In the far north, rainfall follows a strong monsoonal pattern with very dry winters and springs. This pattern changes southwards and has a more or less uniform distribution in Tasmania.
· Soil. Black sheoak grows on a variety of sites from lowland flats to undulating topography and mountain peaks, though it is most common on well-drained hills and mountain slopes. It may be found in rocky gorges, near the edge of swamps, on heathlands, and on sandy lowlands behind sandy dunes. The most common soil types are sand, podzolics, skeletals, and rocky areas where soil is almost absent. Well-drained sites are preferred.
Nodulation Variable; absent on some specimens, prolific on others. Environmental influences are critical for nodulation.
Root Suckering Unreported.
Limitations Not suited for very humid (5,000 mm rainfall) histosols in Hawaii.
Botanic Name Casuarina luehmannii (R. T. Baker)
Synonym Allocasuarina luehmannii (R. T. Baker) L. Johnson
Common Name Bull oak
Main Attributes This is mainly an open woodland species that is tolerant of light frost, poorly aerated soils, waterlogging, and slight salinity. It is often an understory tree that can be planted in association with tall trees. It is suitable for amenity planting in parks or avenues. It will provide satisfactory but somewhat open shelterbelt protection. On moderately good sites its early growth is relatively fast, and there are reports that it will withstand some seasonal inundation by floodwaters.
Description This is a medium-sized tree, reaching heights of 20
m and diameters of 60 cm.
On all except the poorest sites, the main stem is straight and often up to half the total height, after which it divides into several large ascending stems that carry the rather open crown.
Distribution This casuarina has a wide natural occurrence in eastern Australia, from northern
Queensland to eastern South Australia.
· Temperature. In its native habitat summer temperatures
are warm in the south and hot in the north, with mean maximum temperatures of
the hottest month varying from 29°-35°C.
· Altitude. Casuarina luehmannii commonly grows on plains, gently undulating slopes, and, especially in the drier areas, around the edges of swamps and depressions where surface drainage is poor, but it also extends - as a poorer tree - to slopes and ridges.
· Rainfall. For most of its area the rainfall is 380-630 mm, but in northern New South Wales and Queensland it may be as high as 800 mm.
· Soil. Soils show a wide range, from poor, well-drained sands to sandy loams and poorly drained clays, all usually low in nutrients.
Nodulation No nodulation has yet been found.
Root Suckering Under some conditions the species may develop a suckering habit.
Limitations Seed is difficult to obtain and germinates poorly.
Botanic Name Casuarina obesa Miq.
Common Name Western Australian swamp sheoak
Main Attributes This species grows well in wetlands near somewhat saline waterways in both coastal and semiarid inland situations. The species is salt tolerant, and it forms abundant nodules near the soil surface. This tree is closely related to Casuarina glauca and can probably be grown in the same locations and used in the same ways. For instance, it can be planted as a decorative row of shade trees along the seaside. However, it grows in more inland situations than Casuarina glauca and may be even more drought tolerant.
Description This species is a handsome, well-shaped tree that
may reach about 14 m high.
The main stem is branchless for much of its height, and in close stands, if the growing situations is good, it is usually moderately straight.
Distribution The tree is predominantly found along seacoasts and shores of inland saline depressions of Western Australia.
· Temperature. For most of the area the mean temperature of
the hottest month is 29°-34°C and the mean minimum of the coolest
month 5°-9°C. Coastal areas, especially from Perth northwards, are
frost free, but elsewhere there are 1-12 heavy frosts a year.
· Altitude. From near sea level to about 300 m.
· Rainfall. Its native habitat has a pronounced winter rainfall. The South Australia occurrence is in the arid zone, but near the boundary in the semiarid zone. It is drought tolerant down to 200 mm.
· Soil. It often occupies low-lying, swampy flats just above hightide limits and along river banks and the edges of inland salt lakes. In these areas it may grow as pure, dense thickets or as the principal small tree. Soils include a wide range of sands and silts. Other soils on which it has been recorded include pink granitic sands, red clay loams, and swampy soils.
Root Suckering Occurs.
Botanic Name Casuarina stricta Ait.
Synonym Allocasuarina verticillata (Lam.) L. Johnson
Common Names Drooping sheoak, coast sheoak, mountain oak
Main Attributes Casuarina stricta is a graceful ornamental with a spreading form and beautiful, drooping blue-green branches. The branchlets are among the largest (46 cm) of any casuarina. It has demonstrated good growth on irrigated lands in Egypt and has shown early success in Cyprus, India, Israel, and several countries of southern Africa. It grows rapidly (up to 2 m per year), even on poor soils, but after a few years it stops, so that it remains a small tree. The trees form effective shelterbelts and tolerate lopping well, which allows most of the smaller branches of the crowns to be cut off to provide fodder in times of severe drought without killing the trees. On even moderately good soils, open-grown specimens are useful for shade and ornament.
Description Usually only about 6-10 m high, this species typically has a straight, but usually short, main stem. When it is grown in the open, the crown is dense, deep, and almost as wide as the tree is high. The smallest branchlets droop.
Distribution The tree is found on the coastal plains and ranges of New South Wales, Victoria, South Australia, and Tasmania and grows from near the high water mark to inland sand dunes.
· Temperature. The tree probably requires a temperate
climate. In its native habitat mean minimum temperature in winter is from
-2° to + 5°C; mean maximum in summer is 15°-32°C.
The number of frosts varies from 0 to 40 per year.
· Altitude. The tree is found from coastal headland areas to tablelands at about 800 m elevation.
· Rainfall. The 50th percentile rainfall is within the limits of 600900 mm, with the lowest on record 250-375 mm.
· Soil. Casuarina stricta grows on dry ridges and rocky ground, poor coastal sands, and saline soils. It is found growing in salt-spray and wind-affected coastal sites.
Nodulation It nodulates well.
Root Suckering The trees coppice vigorously with shoots from the cut stumps. It is a species likely to produce thickets of suckers, but it is not an invasive weed.
Limitations Where the tree is lopped for fodder in times of drought, little natural regeneration is found.
Botanic Name Casuarina torulosa Ait.
Synonym Casuarina tenuissima, Allocasuarina torulosa (Ait.) L.Johnson
Common Names Forest sheoak, rose sheoak
Main Attributes This species produces better timber than other casuarinas. The wood is less liable to checking and splitting and this is the only species that is commercially sawn for construction timber in Australia.
Description This is a handsome tree, attaining 25 m in height and I m in diameter on favorable sites. The bole is often more than half the tree height, the main branches are spreading to erect, and the crown has an open appearance.
Distribution Native to the coastal ranges of eastern Australia from northern Queensland to southern New South Wales, this tree is associated with wetter forests than most Australian casuarinas. It is shade tolerant and typically grows as an understory species in open forest or grows in tall open-forest formations.
· Temperature. Winter minimum, 2°C; summer maximum,
31°C in its native habitat.
· Altitude. Sea level to 1,100 m.
· Rainfall. 900-2,500 mm evenly distributed or with a summer maximum often in areas with a relatively dry spring.
· Soil. Casuarina torulosa adapts to a wide range of soils from sandy alluvials to compact clays. It has been recorded on steep slopes, moderate hillsides, tablelands, and undulating lowlands, while the soils noted include tertiary basalts, rhyolite, quartzite, various sedimentary rocks, sandstone, and shale.
Nodulation Observed on most specimens examined. No quantitative information.
Root Suckering Unreported.
Limitations This species grows on poor soils, but not as poor as those where the other common eastern Australian species, Casuarina littoralis, grows (page 80).