tasmanian blackwood - New Zealand Journal of Forestry

TASMANIAN BLACKWOOD
By C.D . Gleason
Abstract
Tasmanian blackwood (Acacia melanoxyloni is an erect Australian forest tree which in exceptional conditions may reach
130-150 cm diameter at breast height, 40-45 m in height and live
over 200 years. The species prefers a mild temperate clipate and
moist soils, but will tolerate lowfertility orgleyed soils. It develops
best on sheltered sites and in the presence of a nurse species or
may be grown in "light wells" or canopy gaps.
l be species has had a reputatzon smce the 1 9th centuryfor providing high-qualityornamental timberfor use in turnery, cabinet
and furniture making and as panelling. The dark heartwood,
which forms early, is particularly sought after. Logs are readily
sawn or sliced for veneer; the timber is easily seasoned.
As an exotic it has been most extensively grown in India and
South Africa and shows promise in New Zealand, especially on
the West Coast of the South Island. Rotations of40 years should
produce trees of50-60 cm dbh and with an acceptable amount of
heartwood. Pinhole borers and theghost moth,found in Northland,
may prove limiting.
Much interest has been generated in Tasmanian blackwood
(Acacia melanoxylon R. Br.) following its inclusion as a desirable species in the New Zealand Forest Service Policy for
speciality timbers (NZForest Service 1981).Blackwood is a
species capable of satisfying many of the end-uses met by indigenous woods and imported timbers. It has been promoted
as an intrinsically high-value species with better economic
prospects than radiata pine in some situations.
Information from an Australian Study tour together with
a review of available literature is presented in this paper to
establish the history of blackwood and a perspective for its
promotion as an afforestation species with particular relevance to forestry on the West Coast of the South Island.
BLACKWOOD REVIEWED
Description
Blackwood is an erect tree when forest-grown but inclined to
become bushy when open-grown. Bark is furrowed, rough
and dark brown when mature; the boles of larger trees may
develop flanging and fluting. The olive-green foliage of blackwood makes a sharp transition from feathery bipinnate
juvenile leaves as a seedling to straight slightly curved
lanceolate phyllodes that predominate from the second growing season. Creamy-whiteflowers, attractive to bees and flies,
appear in early summer and the small shiny black seeds
mature by late summer even on quite young trees (deZwann
1980b).
Ecology and History in Australia
Blackwood is native to south-eastem Australia and widespread as a shrublsmall tree in many forest associations of
The author, Curt Gleason, is a principal jorester in the New Zealand Forest
Service at Hokitika (see also cover photograph and caption).
6 N.Z.
FORESTRY MAY 1986
Queensland, New South Wales, Victoria and South Australia
(Beadle 1981).Large trees are found only where soil moisture
is plentiful. The species shows optimal-development in the
swampy bottom-lands of North-West Tasmania (Hall et a1
1970)and though once more widely distributed,sizable stands
are now restricted to Smithton District. Blackwood forests of
this region occupy variably-textured, sometimes gleyed soils,
that require drainage for successful conversion to pastoral
farms. During winter these low-lying forests are often inundated for weeks at a time and log extraction is restricted to
the driest months.
Tasmania's blackwood swamps" are intricate mosaics of
various phases of blackwood regeneration,tea-tree (Leptospermum and Melaleuca spp.)and swamp gum (Eucalyptusovata).
Virtually all of these areas are regrowth forest arising from
earlier milling, fires or abortive farming.
Pre-settlement swamp stands were sparsely dominated by
blackwood though regrowth areas are now frequentlydenselystocked (R.Mesibov pers, comm.). Browsing of blackwood
regeneration by waliabies can be very severe and local researchers regard fire-induced dense tea-tree as important
' 'natural-fencing'' and a precursor to successful regeneration.
Tea-tree also encoura es develo ment of straight branch-free
boles, the blackwoodgeventual y "crowning-out" over their
natural nurse.
"
P
. . . substantial quantities of blackwood
were traded world-wide and the timber
became remarkablv cosmo~olitan.Because
it was regarded 2s a high-quality timber
Tasmanian blackwood found its way to
19th century markets in the United
Kingdom, New Zealand, South Afkica,
United States, Denmark, Holland, France,
Germany and South America.
At maturity Tasmania's blackwood may reach 130-150cm
dbh with heights of 40-45 m on the best sites (ArthurRiver),
more commonly 75-90 cm dbh and 30-35 m height.
Longevity on the best sites can be 200k years but trees over
120 years old are exceptional. In swamp forest viewed by
the author, standing mortality appeared common amongst
trees about 80 cm dbh.
Throughout most of its natural range the climate experienced by blackwood is mild temperate or nearly sub-tropical
with yearly rainfalls of 800-1800mm and winter frosts rarely
exceeding a few degrees Celsius. Well-establishedyoung trees
planted in Canberra, A.C.T.,were killed outright along with
hundreds of other native and exotic species in an abnormally cold dry winter (Powell 19711 but overall the Australian
distribution of blackwood seems more determined by moisture availability than temperature.
Blackwood was an early export from Tasmania of some note
for being ". . . one of the few wattles to reach commercial tree
size" (Rule 19671,and the state became well known for both
blackwood and blue gum (E,globulus)production. With hindsight it would appear that early use of the resource was profligate;most land destined for farm settlement was wastefull
cleared by fire in advance of utilisation (Hutchins 1916Y
Nonetheless substantial quantities of blackwood were traded world-wide and the timber became remarkably cosmopolitan. Because it was regarded as a high-quality timber
Tasmanian blackwood found its way to 19th century markets
in the United Kingdom, New Zealand, South Africa, United
States, Denmark, Holland, France, Germany and South
America.
Within Australia, blackwood quickly established itself as
one of the very best native woods for those reasons that attracted overseas buyers. An especially handsome timber that
finishes very well, it was employed in quality furniturelcabinetwork, cooperage and also met the rigorous s ecifications required of an international ships timber and o carriage
and coach work. A New Zealand Royal Commission noted:
"The timber is much prized in Australia, where it is used for
furniture of the highest class and for ornamental woodwork
indoors . . ." (NZParliament, 1913).
The early boom production soon dwindled; now total annual Australian removals average about 10,000m3 (Appendix I). Blackwood is still recognised as an outstanding cabinet
wood throughout Australia, though mainland supplies are
now insignificant (Baur 1972).The international trade has virtually disappeared but glimpses of the golden past are evident from references to blackwood in international timber
journals and books (Lamb1948;TRADA 1980;Empire Marketing Board 1932; DSIR 1956; Harrar 19411.
Blackwood timber remains remarkably well distributed in
Australia, originating as it does almost solely from Tasmania
and virtually one processing plant (Britton Bros Ltd, Smithton).Swamp forests generate some of the annual cut but in
the short term the bulk of the allowable cut will continue to
arise from "understorey logging" of mixed eucalypt high
forest associations in Smithton District and elsewhere in the
North-West. Mill logs are supplied in random lengths; logs
greater than 700 mm s.e.d. are rare and small diameter
material (250-400mm s.e.d)is routinely converted.
Dead trees are utilised albeit reluctantly as although the
heartwood is sound, it is usually dry and contains pinhole
borer damage. Logs are sawn in no special manner, if anything backsawing or flatsawing prevails, but close attention
is given to maximising conversion by recovery of short lengths
(0.8-1.0mi and re-sawing of large butt slabs to recover further shorts. Superior logs are carefully sawn to maximise the
yield of veneer baulks and these are exported to mainland
plants in 12/ielbourne,Sydney and Brisbane or utilised in Brittons' recently commissioned veneer plant. Veneer factories
slice blackwood both cold and hot. Plants visited in 1981 commented upon the problems of colour and density variation
in the species and the reduced availability of larger-dimension
quality baulks.
Because mainland buyers prefer to resaw material to order,
the sawn outturn is kept in as large a cross-section as possible. Small dimensions are retained and dried locally: this
material appears to be the core supply for the Tasmanian industry which absorbs about 60% of the blackwood cut. Enterprising craftsmen extract minor quantities of limbs and rough
toplog material from cutovers for furniture, turnery and
sculpturingwork, thus capitalising on blackwood's figure and
depth of grain. Whilst such small craft enterprises typically
f
season their blackwood by racking under cover for several
years, industry's commercial seasoning practice in Tasmania
normally relies on air-drying25-40 mm boards for 6-8months
down to 20-26%moisture content (m.c.)followed by3-5 days
in a low temperature kiln.
Better ambient conditions at Melbourne and Sydney timber
yards are employed to air-dry similar sizes to 11-12% m.c.
without kiln treatment; larger dimensions take considerably
longer and some material is seasoned in sheds for 18-30
months. For urgent supply, kiln drying is used but at A.H.
Hasell Limited, the major mainland retailers, pride is taken
in natural seasoning and indeed forms a marketing feature
for this traditional product. Because blackwood sells at prices
some three times that of comparable grade eucalypts or pine,
longer seasoning times are tolerable and viable. Research into
much faster methods such as high temperature drying has
been moderately successful (Cuevas 1974; Fung 19761.but I
believe is unlikely to be applied commercially in the near
future.
Active management of Tasmanian blackwood, particularly in Tasmania, was advocated by early forestry authorities:
"The blackwoods, on the other hand, possess the common
characteristic of the wattles of reproducing freely, especially
after firing, and of malung rapid height growth in the first few
years, qualities which, when associated with the excellence
of its timber, should ensure that it will be iven adequate attention by the foresters of the future,whi e its partiality for
low-lyingwetlands which can be rendered suitable for intense
settlement only by the application of expensive drainage
schemes to some extent guarantees the retention of suitable
areas under forest" (Jolly1928).Unfortunately, management
of the blackwood resource was not pursued to any real extent and in keeping with the best colonial traditions conversion of blackwood forest to farmland proceeded apace. By
using certain Ministerial powers, some controls on cutting
were instituted, (Steane 1937)and a continual yield of blackwood has been possible through to the present day.
Sharp interest in blackwood forest management has landled
in Tasmania (Forestry Commission of Tasmania, Annual
Rpts. 1971-81)and recent research studies, evaluations and
surveys have resulted in firm pro osals for management of
Smithton District swamp forests For. Comm. of Tas. 1981).
Concurrently the Commission reduced and centralised the
allowable cut of blackwood to one plant and raised royalties
- the 1980181 Annual Report states: "Premiums for blackwood . . . increased as a reflection of Commission's policy
of increasing sawlog values and achieving margins for quality species like blackwood . . ." Their potential blackwood
working circle is perhaps up to 10,000hectares, principally
in the North-West; a sustained yield of 1.2-1.5m3ihaiyr has
been calculated by the Commission based on clearfelling and
supplementary planting, shelterwood systems, and production thinning of dense regrowth stands.
Blackwood timberiveneer combinations may be viewed in
"up-market" ends-uses in Melbourne and Sydney, typically
decorative cabinetwork, furniture, panelling and quality
restoration. The demand seems to greatly exceed the tiny
supply - blackwood removals are only 0.12%of Australian
sawloglveneer production (Dept. Primary Ind. 1983) - and
I suspect the dis arity will increase as alternative timbers
become scarcer for example, native mainland rainforest
species) and more expensive (forexample, imported tropical
hardwoods).
?
P
7
Cultivation as an Exotic (outside NZ)
Foresters; arboriculturists and nurserymen were quick to extend the range of tree species discovered in New h70rld continents and the far Antipodes. The eucalypts, for instance,
were very rapidly introduced around the world and no doubt
the distribution of other potentially valuable tree species was
facilitated by colonial linkages. Australia's blackwood, for instance, was established in South Africa by 1865 (de Zwann
MAY 1986 N.Z.
FORESTRY 7
19801, 111 lrldia by 11842 (Troup 19321 and Ilawaii l,y 1919
iNelson and Schul~crt1976. These early plantirigs were probably associated wlth extensive trials of the tanni11-richwattles for use in local leather rndustries. The species 11'.1:5 1>een
planted operationally in Italy iPavari 19441, Spain (deArana
Santoyo 19471, Arqentina iCrovctto 19471, Ceylon and 1%
cstine iTroup 1932) and Chile (F Schlcgcl pers comm.1.It is
also reported from kithiopir~(van Hrietenback 1961) , (:ongo
(Flemal 19611 and Japan iFul<uda 1968).By area t~lackxvood
is prohably most extensive in India followed by South Africa.
(:ornprchcnsive rcscarch into blackwood has bccn a feature
of the latter natron since 1974 and South Africm studies
donlmatc recent litcraturc.
India
In the temperate Nilgiris region of India, blackwood was \veil
uaturalised by the turn of the century and is now utilisect Lor
fuelwood and utility timber wlde the follage IS l~arvestcdfor
cattlc fodder (Samraj and Chinnaniani 1081; Sekhar and
Kukreti 19701, Natural re-establishment can reinstate harvested areas but ubiquitous grazing encourages supplementary plantilng preferably using potted stock. Giveil the site
s
and growth rate,
requirements of blackwood, ~ t palatability
it would seem unlikcly that the species will be actively promoted beyond Nilgiris.
Hawaii
Establishment trials with hlackwood in the wide-rangingsites
available have shown errat~cresults. From a survey oi black^
wood plantings throughout Iiawaii (Nelson and Schubcrt
1976.)and the live and ten year results of extenswe replicated
species trials (Whitesell and Waltcrs 1076;Whrtesell 1970)il
appears that establishment is typically mediocre or a failure
but occasionally excellent with annual growth of 1.2 rn and
diameter growth of 1-1.5cm per annurn. Merchantabk stems
have bccn harvested; in fact the timber closely resembles that
of the prized native Hawaiian acacia, Acacia hou.
South Africa
Of little significa~iccat first rn plantat~ons,in so far as extent
and yield are concerned, blackwood has heen described as
a "species of minor importance" il'oynton 10571. Thcrc is
mention of blackwood in early annual reports (llcpt.For S.A.
1937, 1940 - earlier reports not available)but statistical s u m
maries oi South African forestry do not present area tables
for blackwood nor wood removals till 1959 ( I k p t . For. S.A.
An. Rep. 19.59).hlerchantable timber trees can develop in
the higher rainfall areas from the Cape to Northern Transvaal
but commercial supplies come almost exclusively from the
George-Knysna locality of South Cape where t)lackwood was
planted amongst debilitated indigenous forest.
Native forest covers about 0.5%of South Africa and timber
shortages were a problem from the earliest days of European
settlement. Afforestation for the large wattle bark industry
began in thc 1880s but the severe timber shortages of World
War I stimulated a crash programme of plantation establishment based on fasr-growingexotic pines (includingP. radiata)
and eucalypts. Supplementary planting of blackwood appears
to have been a facet of a general forest conservation policy.
Indigenous forests had supplied the pioneers with both utility
and specialty timbers and South Africans today place great
value upon period architectureand furniture and consequently traditional woods, particularly stinkwood, Ocotea bullata
and yellow wood (Podocarpusfalcatusand P. lat$folius).The
relatively recent develo ment of a very strong demand for
blackwood timber an the consequent interest of forest
growers are linked with the fortuitous similarityof blackwood
to stinkwood - thus in local descriptions: "The wood varies
in colour from almost black through brown to a light grey.
In general, it is well figured, mainly on account of the growth
rings. It closely resembles st~nkwoodat times and is in fact
2
-
8 N.Z. FORESTRY MAY 1986
By area blackwood is probably most
extensive in India followed by South Africa.
Comprehensive research into-blackwood has
been a feature of the latter nation since
1974 and South African studies dominate
recent literature.
gradually being substituted for this more valuable wood,
though it lacks its characteristic sheen" (Perry 1973);from
another author: ". . . Acacia melanoxylon is nevertheless orie
of the few exotics which yield a good furniture and flooring
wood, the heartwood being of excellent quality and not unlike
walnut or stirkwood" G u t 1965).
Very high prices are fctchcd by blackwood at log auctions
(Appendix I) but buyers arc discerning and log values show
great variation in accord with grades which relate to size and
heartwood content (deZwann 1982).There seem to be no particular problems in utilisatiorl and the timbcr of blackwood
is seasoned with littie difficulty (Immelman et a1 1973;Hartwig 1964; Anon. 1942).
Consumer enthusiasm for blackwood in South Africa has
encouraged a systematic rcsearch programme in silvicu!turc
and tree improvement. Accounts of this work are noted in
Forestry Department annual reports from 1967,and in various
publications (Harrison 1974; 197,5a,b; de Zwann 1982).My
interpretation of the South African position is:
(a) Large container stocks of blackwood can be grown quickly from seed and are the basis for good field establishment
provided browsing by deer andlor rodents is prcvcnted
and the site is not droughty.
(b) Commercially-sipificantprovenance differences or select
genotypes will probably be determined by the tree improvement programme underway focussing on tree form
and heartwood properties. Ve etative propagation by
root cuttings is possible and wi 1 probably be employed
in tree improvement work.
(c) Experienced deci'sions on siting of blackwood and its
silviculture are especially important for successful plantations, particularly:
- avoiding exposed areas;
- manipulating stand spacing and tending practices to
encourage good stem form;
- planting blackwood in mixture with appropriate nurse
species (includingradiata pine) whcrc exposure threatens windthrow;
- selecting deep moist organic soils in regions which experience a dormant season to encourage maximum
heartwood development .
(d) Utilisation will continue to rely on the resource of "old
growth" enrichment-style plantings from indigcnous
areas till younger plantation-grown material becomes
available. Merchantable-sized trees may be produced
from plarltations on rotations of 35-40 years given timely thinning and pruning. However, the very high values
received for blackwood are closely linkcd to heartwood
content, colour and log diameter - to grow the best quality material will probably require 50-70 year rotations.
Over most of South Africa edaphic conditions are unsuitable for proper blackwood tree growth and the species may
even be relegated to the status of a silviculturalweed (Donald
1971)or in the presence of regular fire, an ecological weed (I Iall
1961).Although relatively insignificant compared to other
weed species, fear of exotic plants naturalising themselves is
keenly felt in South Africa and blackwood planting is prescntly restricted to only a minor area of the Southern Cape.
B
I
Extxrience in New Zealand
~ a r i introductions
y
of blackwood to New Zealand date from
mid-19th century. Systematicdevelopment of plantations by
the Afforestation Branch of the Lands and Survey Department
placed considerable emphasis on quality hardwood planting.
Early planting in the Rotorua District, begun in 1896,
established hundreds of thousands of Catalpa speciosa and
Acacia melanoxylon, the latter promoted for eventual end uses
in - "Furniture, shop fittings, pianos, railway purposes,
billiard tables, etc." (Dept.Lands 1909).Interestingly, radiata
pine did not appear on the early list of desirable timber species
and as of 1909 more blackwood had been established at
Rotorua than P. radiata and P. muricata combined! The Royal
Commission on Forestry (NZ Parliament 1913) acknowledged the intrinsic worth of blackwood and other species but
pragmatically decided to plump strongly for radiata pine.
With the formation of a separate New Zealand Forest Service
in 1921 and the quickening appreciation of impending timber
shortages, the view that "quantity beats quality" became axiomatic and participants in the 1925-35planting boom probably never paused once to consider afforestation with
species such as blackwood.
Nevertheless, tree enthusiasts maintained some interest in
blackwood, encouraged by authorities who extolled the
qualities of the species, such as Mathews (Mathews1905)who
wrote: "This species requires deep soil with a cool moist bottom to do well. It is probably the hardiest of the large growing acacias, and one that should be largely planted in this
colony".
Consequently blackwood is not infrequently encountered
in older homesteads, parks and gardens and the scattering
of trees about the country is no doubt testimony to its aesthetic qualities as much as to perceived timber value.
During the 1950s,New Zealand Forest Servicedirected trials
and operations into indigenous cutovers, especially podocarphardwood types, with the aim of "enriching" these areas with
introduced species of greater productivity. Acacia melanoxylon was selected for enrichment trials by the Forest Research
Institute in 1960161as the species was seen to possess some
of the desirable characteristicsfor such a role, especiallyhigh
value, rapid early growth and a degree of shade tolerance (NZ
Forest Service 1962).Blackwood proved a successful enrichment species at the Manukau Forest trials (NZForest Service
1970)though management operations never really developed
in their wake. Similar investigations were launched in West
Coast beech and podocarp-hardwood forests employing
eucalypt species and blackwood. The early plantings of blackwood in 1966,1967and 1968were very severely browsed by
possums, resulting in low survivals, variable growth and poor
form (D.A.Franklin pers, comm.).The degree of damage was
far greater than anticipated from earlier work (NZForest Service 1966)and occurred for more than just one season. Wire
netting around seedlings obviated such early browsing but
the alternative eucalypts species required no such protection
and further trials in enrichment and/or supplementary planting did not include blackwood. Possum numbers have reduced dramatically from those times, however, and similar
intensity browsing has not been experienced in comparable
operations over the past few years in Westland (NZForest
Service 1982a).
Early afforestation with blackwood did not produce appreciable stands and most plantings were poorly tended.
Nonetheless utilisation experiencewith New Zealand grown
timber proved favourable (Weston 1957; Anon. 1961:
Buchanan 1964;Foley 1970;Barr 1966,1978)though the fraction of recoverable sawlogs has been small to the oint where
at least one stand was felled to waste (Gibson 1978 . Successful
establishment proved elusive in many situations (Hinds 1969;
McKellar 1971); and this tempered enthusiasm for blackwood
(Chavasse 1970). Blackwood did qualify for afforestation
grants under the Encouragement Grant Scheme (Tho?@on
19711, but its selection was not really a reflection o field
e
achievements, though sustained efforts were made in some
localities with notable success in the Auckland Regional
Authority Hunua Forests. A comprehensive survey of North
Island blackwood by the Forest Research Institute (Nicholas
and Grallelis 1978)illustrated clearly the constraints to blackwood silviculture but engendered confidence that the species
could be successfullycultivated in New Zealand (NZForest
Service, 1978).When in early 1979 the Forest Service organised
a workshop on special-purpose timber species, blacLwood
was received well, despite scant management experience of
its establishment and tending requirements (Purey-Cust1979).
Following the 1981 release of the Forest Service Policy on
specialty timbers, blackwood has been planted out on many
forests in both the private and state sectors. Further guidelines
and re orts are now to hand, especially through FRI researchers NZ Forest Service, 1982a,b;Barr 1982).A wide range
of establishment trials are in the ground and provenancetesting of blackwood has commenced (M. Wilcox pers.
comm.). The implications from earlier survey findings of
Nicholas and Grallelis regarding blackwood seem more or
less unaltered by the past few years' experience viz:
(a) Blackwood is remarkably site-tolerant in terms of temperature, rainfall and soil moisture but good-form trees
develop only where they are sheltered from wind by
topography, nurse-vegetation or mutual protection;
ib) Best results are achieved where trees grow in light-wells
or canopy gaps which encourages straight stems, light
branchin even to some extent self-pruning;
ici Pure stan s or mixtures with compatible nurse crops are
alternative management regimes but in either instance
silviculture must be flexible, sensitive to site and stand
differences and attentive to variable tending treatments;
(d) On good sites rotations of 40 years should produce trees
of 50-60 cm dbh though shorter rotations may be
possible;
ie) Llamaging agents occur of which the most significant are
puriri or ghost moth (Aenetusvirescens) and native pinhole
borers (Platypusspp.).
Thorough research into New Zealandgrown blackwood is
constrained by the limited extent and age distribution ,of
plantings. Local data for wood density and shrinkages (Haslett
1983;B. Youn and D.L. McConchie pers. comm.)differ little from cpotejoverseas values (Greenhill1937;Kingston and
Risdon 1961; Bolza and Kloot 1963;Van Vuuren, et a1 1978)
with similar wide variation in between-tree basic density.
In an exhaustive seasoning trial using timber from Whaka
State Forest Park stands, Haslett (1983) confirmed
blackwood's straightforward drying properties although drying rate proved quite variable. Haslett's recommended twostage drying (airdrying to 30% followed by luln drying without
reconditioning) is routine international practice for seasoning hardwoods.
P
3
EVALUATION
(With emphasis on the West Coast)
Private and State foresters accept the spirit of special purpose
timber species establishment but are reluctant to commit
resources of land and finance to. substantial programmes, particularly when the choice lies between relatively unknown
demanding species and easily-managed, well-known and
readily marketable radiata pine or Douglas fir. Progress
towards achieving afforestation targets of the 1981 Forest Service Special Purpose Timbers Policy has been well below expectations, indicating a general lack of confidence in the
pursuit of special-purpose working circles and/or difficulties
in justifying them. In Westland as in other regions, treegrowers' apparent faith in utility softwoods such as radiata
pine reflects a scepticism that specialty species will necessarily
return sufficient revenue margins to compensate for the
greater costs and efforts incurred in growing them. The history
of timber utilisation in New Zealand supports such conservatism. If one reviews the utilisation of native woods, most
MAY 1986 N.Z.
FORESTRY 9
notably the hardwoods, the industry-market complex has
been rarely discriminatory with regard to special purpose
wood quality but very strongly influenced by timber species'
suitability for construction end-uses and ease of seasoning.
In malung a critical evaluation of blackwood's potential it
seems sensible to employ three criteria - commercial value
and acceptabilit , silvicultural characteristics and growth,
and utilization eatures.
Commercial Value and Acceptability
r
Blackwood timber has demonstrated an enviable marketability, initially in far-flung export markets and at home, then
subsequently maintaining an elevated status as a semicultivated species in Australia and South Africa. It is significant that the value of blackwood timber is not tied to superior
characteristicsof an old growth resource such as availability
of large-sized quality logs, plentiful supply, low production
costs, nor proximity to markets - quite the reverse applies.
Certainly there appear to be cultural influencesthat are pricesupportive: in Australia the species is historically linked to
an earlier VictorianIEdwarian period of rich wood-furnishing
and colonial well-being (similarto the "nostalgia margin" experienced in New Zealand by kauri);in South Africa a fortuitous resemblancetothe much-valued traditional stinkwood
undoubtedly favours blackwood considerably. Nonetheless
judging by the wood consumption tastes of New Zealanders,
there is every reason to expect locally grown blackwood to
receive similar appreciation though value margins seem
unlikely to match South African figures. The darker colour
of blackwood will handicap its across-the-boardmarketability
duing periods of preference for lighter timbers though the
same constraint could be laid against black walnut, Indian
rosewood, teak and South American mahogan . It is worth
noting that the Commonwealth of Australia's o&cialpresentation at the wedding of the Prince and Princess of Wgles was
a gift of silver platters within a blackwood box!
Silviculture and Growth
Blackwood possesses a number of features that favour its
cultivation in New Zealand generally and the West Coast:
(a) Seed may be stored for long periods and planting stock
may be raised relatively quickly as bare-rooted seedlings
or containerised stock. Planted seedlings can recover from
damage or dieback at planting by basal sproutin ; in most
instances early height growth of planted stoc is rapid
(0.7-1.0m).
(b) Trees can be established successfully in the face of competing vegetation including side-shading if given a "lightwell" space - it is a proven enrichment species in terms
of growth (Fig. 1).
(c) Blackwood appears tolerant of our winter cold (up to
8-10°Cfrost at least) and will grow in soils of relatively
low fertility and considerable gleying. Over a range of
sites, diameter growth of 10-15 mm per annum appears
achievable and given rudimentary tending, crop trees of
50-60 cm dbh should be realised on 40-year rotations.
(d) Heartwood, the substanceof value, forms at an early age
and trees grown on rotations of 40 years should contain
an appreciable heartwood content in their butt sections.
Growth habit in blackwood facilitates formation of large
branchy crowns above single butt logs, thus maximising
production of the desired end-product and minimising
toplogs.
(el Young trees may be green branch-pruned and leaderpruned without particular caution or prophylactic
treatment.
(f) The species seems remarkably healthy and vigorous over
a wide range of world environmentsparticularly temperate
climates.
On the other hand blackwood is handicapped during
establishmentyears by its palatability to possum, deer, goats
E
10 N.Z.FORESTRY MAY 1986
Fig. 1. Group of blackwood, aged 18,planted into podocarp-beech
forest after extraction of all podocarps. Trees were badly damaged
by possums in their early years, causing stem malformation.
and domestic stock. Much more attention to animal control
is needed for blackwoad afforestation than most other timber
species.
As with many hardwoods, blackwood is vulnerable to common weedicides used about conifers (2,4,5-T,hexazinone,
etc.),and off-site spray drift damage to blackwood must be
guarded against. All weedicides, pre-planting or otherwise
em loyed, must be judicious1 applied amongst blackwood
wit! so little empirical know edge to hand.
Although regenerated stands have established in spot locations (Bartlett's stand at Silverdale for example) there is no
evidence from New Zealand to indicate the species poses a
weed threat, least of all amongst indigenous forest (NZForest
Service 1983).A more significant unknown is the potential
influence of ghost moth and the pinhole borers (Zandvoort
1983)- attack by these insects can reduce the eventual outturn of quality timber or veneer products. Ghost moth is
found only in the North Island and damage, though frequent,
appears to be confined to the natural defect core of logs.
Serious pinhole attack similar to that experienced by eucalypt
species has not occurred in older enrichment plantings but
close monitoring is warranted.
Blackwood is iorm-sensitive.Although mixtures with nurse
species are probably advisable for open country in
Westland, there is scope for establishing blackwood as a
supplement amongst second-growth indigenous forest as a
viable silvicultural alternative to more intensive clearing for
plantations of other utility or specialty timbers. West Coast
soils are rarely fertile and often gleyed but low fertility and
high soil moisture levels seem only marginal limitations to
blackwood.
Utilization
The described timber properties of blackwood, physical and
aesthetic, are well documented;judging by them and established end-uses it is certainly a special purpose timber par excellence. Desirable wood properties of blackwood are not
?
c o n h e d or concentrated just to large-sized old growth
material but are repeated within regrowth trees including
relatively young trees grown on shorter rotations outside
blackwood's native range. Likewise the disaclvantageous
features of blackwood timber, pronounced variability in colour and density, arc also repeated in cultivated stands. They
will constitute an irritation to New Zealand processors and
end-users but are not a serious fault inhibiting eventual
utilization.
No special techniques arc required to saw blackwood;
srnall-diameter, fast-grown logs do not develop the growth
stresses of some eucalypt species and good sawn conversion
can be expected from trees grown on 40-50 year rotations.
More ~mportantly,seasoning blackwood timber presents few
of the problems often associated with hardwoods such as surface checking, cupping, and internal collapse. Sirnplc twostage drying, air-drying for 12-20weeks followed by conventional kiln or dchumidilicr drying sllould produce quality
snatcrial cornrnesxuratewith quality end-uses altliough some
drying degrade may develop where sawlogs contain apprcciablc tension wood.
There is every reason to expect
concomitantly greater returns for logs
and/or in stumpages from New Zealand
blackwood vis a vis utility pines that should
adequately compensate planters for higher
growing costs, lower volume production and
longer rotations. Domestic and export
markets appear open to blackwood timber
products.
Seasoning is a critlcal variable in assessing timbers for
potential utilization in New Zealand. inciustry's traditional
resource has been easy-to-dry species that require little
technical skill, effort or time (Glcason 1982)and new timbers
are rated relative to these past experiences. lilackwood is
easier to dry than most eucalypts, particularly the ash-group
and would seein no nmrc difficult or deinanding in this regard
than silver beech (Nothofagusmmziesii)or tawa (Beilschmiedia
tawa).
CONCLUSION
The timber properties of blackwood arc recognised as enconipassing the features of a vcrsatilc special-purposehardwood.
The species has dcinonstrated its suitability for such end-uses
in demanding and competitive world markets and in this
arena has attracted high prices.
There is every reason to expect concomitantly greater
returns for logs andlor in stumpages from New Zealand
blackwood vis a vis utility pines that should adequately compensate planters for higher growing costs, lower volume production and Ion er rotations. Ilornestic and ex mrt markets
appear open to lackwood tirnbcr products. T e species is
relatively easy to saw and season or produce veneer from and
no special utilization skills or facilities are required. Siting of
blackwood is critical and success or failure oi plantations may
rest on the ability of growers to recognise appropriate sites.
Attack by pinhole borers and ghost moth is probably the most
serious limitation to blackwood forestry in New Zealand and
this matter warrants close monitoring. Suitable locations for
relatively extensive stands of blackwood appear widespread
on the West Coast of the South Island particularly within some
indigenous cutover areas. The predominance of low fertility
E
L
soils with variable gleying in a mild wet climate is no great
coristraint to blackwood cultivation.
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APPENDIX I
Published black~vood log production and prices from
Tasrnnnla Icronn tenures' and South Afrlca
SOUTH AFRICA
TASMANIA
Year
19711'2
19?2i73
1973174
1'17317;
107.5/76
1976177
1977178
!Y 78171)
1079/80
1980181
1981182
19,42183
1%i3183
'1.880
li.878
$12.67 .\LIS
'3
S13 58 .\us
S13 I 6 A u s
9.361