Melaleuca irbyana is a small tree to about 8 metres tall, spreading to about 3 to 4 metres wide, with spongy-papery bark.
It grows in disjunct patches over its natural range. In NSW, it is found around Grafton and south of Casino. In Queensland, it grows roughly between an area bounded by Beaudesert, Logan City, Brisbane, Gatton and Harrisville; with a disjunction to north of Esk and then a large disjunction found near Injune.
It is typically found in dry sclerophyll woodland on swampy ground / poorly-drained sites.
This is a listed threatened species in NSW and Queensland.
Melaleuca spp. can present with simple and alternate or opposite leaves. In this species, leaves are alternate and somewhat appressed to the stems, elliptic to ovate to 5 mm long and 1.5 mm wide, with apices pointy, dark to mid-green in colour.
In Melaleuca species, flowers are usually arranged in spikes or heads. Within the head or spike, the flowers are often in groups of two or three. Flowers have five sepals (sometimes fused into a ring of tissue) and five petals which are typically small and do not persist on the flower for long.
Like many other Myrtaceae genera, the flowers are conspicuously staminate with each flower having many stamens surrounding one carpel. The stamens are typically fused into five separate bundles (staminal claws) which each bundle sitting opposite a petal (a generally useful identifying feature for the genus to distinguish it from Callistemon). Melaleuca flowers do not have pedicels (sessile).
In this species, flowers are white, scented and held in terminal spikes up to 2.5 centimetres long. Each spike is composed of 3-12 individual flowers with flowers in primary clusters of 3; appearing from September to January. Each flower can have up to 60 stamens in five clusters.
The fruit is a capsule. In this species, they are small and woody, and somewhat flattened, to 4 mm diameter. Seeds are released when capsules mature.
Author’s notes:
In our cold climate garden (near Armidale) plants only reach a height of about one metre. Plants, in another local garden, have grown into a similar size. Melaleuca irbyana grows in open eucalypt forests on poorly drained sites. Our plants are probably restricted in size because they are growing in well drained, rather dry sites.
In our garden plants are grown as foreground specimens in garden beds. Growth habit, foliage and flowers are all attractive features. Tip pruning helps to shpae plants and make foliage much more dense. They grow naturally in heavier (clay-based) or alluvial to sandstone, poorly-drained soils and so may need this requirement to do well. They likley benefit from additional water in dry times.
May be hard to source as it is a threatened species. Check with local native nurseries. It is sold at at least one nursery in NSW (see references).
Propagate from seed and cuttings.
The species was previously known as M. tamariscina subsp. irbyana. M. tamariscina is found in central Queensland.
Fire response unknown. May be able to regenerate from epicormic shoots and suckering or through the seed bank.
The genus Melelauca has been subject to recent taxonomic revision with early and recent botanists including Ferdinand von Mueller and Lyndley Craven (deceased in 2014) proposing to expand the genus to include all Callistemon spp. and others. Craven et al. (2014) published new species combinations which included the renaming of all Callistemon species to Melaleuca, based on evolutionary relationships and DNA evidence and other features.
Currently, the NSW Herbarium advises that the Callistemon genus can still be used.
Melaleuca is a genus of about 220 species, occurring mostly in Australia, but also Malesia and New Guinea. Australia has about 215 species with 210 reported endemic, occurring in all states. NSW currently has 30 species.
Melaleuca – is derived from the Ancient Greek mélas (μέλας) meaning “dark” or “black” and leukós (λευκός) meaning “white”, apparently because one of the first specimens described had fire-blackened white bark.
irbyana – named for L. G. Irby (1883-1964), a Museum Collector who collected the type specimen.
This species is listed as being threatened with extinction at the State level with the category of Endangered. It is also listed in Queensland as Endangered.
NSW Flora Online (PlantNET) – Melaleuca irbyana profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Melaleuca~irbyana
NSW Office of Environment and Heritage – Threatened species profiles – Melaleuca irbyana https://www.environment.nsw.gov.au/threatenedspeciesapp/profile.aspx?id=10518
Burringbar Rainforest Nursery – Melaleuca irbyana sales page https://burringbarrainforestnursery.com.au/plant-search/melaleuca-irbyana-swamp-tea-tree/