SPRINGTIME and the coastal edge of the Wonthaggi Heathland turns bridal. Coast Teatree is lacy with fragile white blooms, trunks standing amid a litter of white petals. Mature stands in other areas are famous for “lovers' walks”. Once you approached Waratah Bay through an avenue of old giants, and the gnarled twisted trunks at Tidal River resemble fossilised licorice. Furniture is made out of the stout sticks and trunks, it is a sought-after firewood and many coastal garden beds and retaining walls are edged/lined with this timber. It holds a place dear in the hearts of beach campers, providing shade, shelter and privacy.
But not for me. I hate it!
Coast (or Victorian) Teatree [Leptospermum laevigatum] extends naturally eastwards from Anglesea to NSW, including Tasmania and the Bass Strait islands, usually on the coastal dunes. A member of the Myrtaceae family, it occasionally hybridises with Leptospermum myrsinoides. (We have found these hybrids at the Wonthaggi Heathland and the Campbell Street bush.)
Ranging from eight to 12 metres, it has a life span of 100-150-plus years, new plants setting seed after five years. Seed capsules can remain unopened on the tree for up to three years at the Prom, responding to water-stress to open – lopping, dry conditions or a fire triggers seed dispersal. The tiny winged seeds can travel a short distance on the wind, but are thought not to be bird-dispersed. Because they are soft-coated, seeds do not remain viable in the soil for longer than 12 months and seedlings need mycorrhizal infections in soils of low fertility (acid siliceous soil). It is believed that Coast Teatree is a relatively new arrival (only thousands or tens of thousands of years old), perhaps a mutant or successful hybrid itself. it certainly tolerates well-drained coastal soils rich in calcium carbonate (shells) with heavy salt spray.
Sounds harmless, a good soil-binder of dunes? Certainly, but this beautiful plant has hidden depths. Fire is its ally. When hit by fire, whether a controlled burn or a bushfire, the tree dies, unable to regenerate vegetatively. Its hard woody capsules are protected and gradually open with a lack of moisture, producing up to 10,000 seeds per square metre [Tim Offor, Victorian naturalist, 1990) on soil temporarily rich in phosphorus levels, the seed viability gauged to be greater than 88 per cent. Seedlings proliferate the following winter, predation by grazers being negligible.
The Prom'n'aides, a group of amateur botanists who monitored post-fire vegetation after the 2005 and 2009 bushfires at the Prom, found that along Biddy's Tack at Tidal River, in mature stands of Coast Teatree post 1951-2 bushfires, the first spring recorded flowering lilies, orchids, wildflowers which had been dormant in the soil for 50-plus years. They set seed, only to be overtaken by Coast Teatree seedlings the next year, up to 600-plus per square metre.
Working in massive swathes of Coast Teatree along Telegraph Track late in 2013, the Prom'n'aides found it dangerous and impenetrable – plants were head-high or taller, camouflaging a pick-up-sticks tangle of dead fallen spars of former trees, spikes lethal to the unwary, branches slippery in the wet. Whole stands of dead trees formed tee-pees in the bush.
Thus Leptospermum Iaevigatum has become an environmental weed, noticed in Port Lonsdale and Frankston in 1935, the Prom from the 1950s, Cape Liptrap Coastal Park and the Wonthaggi Heathland from the 1970s. its dense stands have overshadowing canopy, there is an increase in leaf litter, roots mass beneath soil, there is dessication of the mini-environment, all leading to a decrease in species richness. Walk through any thick stand and note the poverty of species present.
If the newly invaded hectares could be burnt before capsules set seed, the problem could be contained, but at what cost? Heathland plants need 15+ years between fires to prosper. Whole suites of plants would be wiped out.
Unfortunately Coast Teatree has extended west of Anglesea and into interior Victoria, as well as being introduced into Western Australia (Victorian Teatree), Queensland, South Australia, as well as New Zealand, California, Hawaii and South Africa. It has invaded coastal grasslands, woodlands and heathlands, becoming thick species-poor scrub. It has the ability to change the structure, composition and function of the ecosystem to form a monoculture.
Why do I hate it? For all of the above, but Cook did name it because he made a tea from the tips to combat scurvy in his crew – it supposedly still makes a refreshing tea.
Do I admire it? I love the old giants in the camp grounds at Tidal River. Yes, I have a chair made of its wood. And yes, I will admire its bridal purity in the Wonthaggi Heathland come late spring.