Byron Flora and Fauna Study 1999 - Byron Shire Council

A GREENPRINT FOR A SUSTAINABLE FUTURE
Rough-shelled Bush Nut (Macadamia tetraphylla FAMILY PROTEACEAE
Introduction. Rough-shelled Bush Nut is a rainforest tree with edible ‘nuts’ which have been important in the development
of the Macadamia industry. Most current plantations are of hybrids of the Rough-shelled Bush Nut and the Queensland
species M. integrifolia, but Rough-shelled Bush Nut is still sometimes favoured as a rootstock. The conservation of wild
relatives of commercially important species is of particular importance, since genetic material for new breeding programs
may be needed in the future. No Recovery Plan has been prepared. A detailed species outline has been prepared (Quinn
et al. 1995). Rough-shelled Bush Nut is a host tree for the Pencilled Blue Butterfly and the Six-line Blue Butterfly.
Conservation status. Rough-shelled Bush Nut is listed on Schedule 2 (Vulnerable) of the TSC Act, 1995 and has a
ROTAP code of 2VC- (Briggs and Leigh 1996).
Habit. A small to medium, usually densely bushy tree, to 18 m in height (Floyd 1989).
Flowers. Creamy pink to purplish in narrow racemes to about 25 cm long in the axils of the leaves, or from above the
scars of fallen leaves. Flowering from August to October (Floyd 1989).
Fruit. A brown follicle, enclosing one or sometimes two seeds. Ripe January to April (Floyd 1989).
Habitat. Floyd (1989) describes Rough-shelled Bush Nut as occurring in subtropical rainforest near the coast. Also in
notophyll vine forest (Quinn et al. 1995).
Distribution. Confined chiefly to the Richmond and Tweed Rivers, NSW, extending into the Numinbah Valley and Coomera
River, Queensland. Recorded in NSW from the Clarence River; Nimbin; Whian Whian SF; Dunoon; Lismore; Davis
Scrub NR; Victoria Park NR; Wardell; Mooball; Burringbar; Mt Warning NP; Limpinwood NR; Numinbah Creek; Crystal
Creek; Murwillumbah; Bilambil (Floyd 1989). Additional sites reported by Quinn et al. (1995) are at Lennox Head;
Goonengerry; Banora Point; Mt Nullum; Hogans Scrub; Dungay Creek; Maclean; Alstonville. Recently recorded from
Old Bonalbo in the Upper Clarence River (T. Moody pers. comm.). Details of 26 locations in the study area were
compiled, and many more individuals are scattered in the vicinities of these locations. At least seven new sites were found
by the authors during this survey. A population of more than 50 individuals has been reported from upper hill slopes in
Goonengerry (H. Bower pers. comm.).
Regeneration and horticulture. Fresh seed may germinate in 14 days. Selected strains may be budded or grafted (Floyd
1989).
Economic and cultural significance. Rough-shelled Bush Nut has been important in the development of the Macadamia
industry. Plantations have been composed of Rough-shelled Bush Nut in the past, but it has largely been replaced by
varieties with superior processing qualities and shells that can be cracked mechanically. The timber of Rough-shelled
Bush Nut is reddish, hard and tough and prettily marked, but because the nuts are so valuable, the timber is rarely
exploited (Floyd 1989). Rough-shelled Bush Nut also has the aesthetic and ecological values of all native rainforest
species.
Threats and amelioration. Habitat clearing, weed invasion and other edge effects (Quinn et al. 1995). Fire, grazing,
development and roading also threaten Rough-shelled Bush Nut. Hybrid cultivated trees will interbreed with the Roughshelled
Bush Nut so that the pure wild strains may be lost through genetic pollution.
The conservation status of Rough-shelled Bush Nut, the health of populations and their regeneration potential should be
enhanced by weed management, grazing exclusion, fire protection and replanting of surrounding habitat. Measures to
prevent the planting of cultivated hybrid trees within pollination distance of wild trees of Rough-shelled Bush Nut may be
necessary.
176