White Beech: The Rainforest Years (33 page)

Between 1947 and 1985 463 exotic grass and legume species were introduced to northern Australia. (Lonsdale) Of these, only four species were subsequently found to be useful, 43 became listed weeds, while another 17 were found useful but weedy. (Fox, 230)

The worst grasses to be introduced to the Numinbah Valley may eventually prove to be bamboos. Lately a new craze has been spreading, this time for the planting of long lines of bamboo, in this case
Bambusa arnhemica
. These may be simply windbreaks, themselves made necessary because of the clearing of forest. Though
B. arnhemica
is a clumping rather than a running bamboo, it does spread outward in rings around a dead centre and will gradually become bulky and difficult to remove. The rush to bamboo could also be a response to the increase in noise and nuisance, as our remote area has become a favoured site for boy racers and bikies and parties of howling schoolies. This human infestation is an understandable cause of fear and loathing on the part of the locals, but if bamboo barricades are to be their response the result will be catastrophe. A bamboo with any degree of tolerance for shade would be an utter disaster for regenerating rainforest.

The grasses were just the beginning; as O’Reilly says, ‘swift in the wake of a new grass came the dreaded fire-weeds, tobacco, inkweed and lantana.’ (118) CCRRS has to deal with all of these. Fireweed is the name given in Australia to a South African ragwort,
Senecio madagascariensis
, which was first reported from the Hunter Valley in 1918. It is now ubiquitous in south-east Queensland. As it is poisonous to horses and cattle enormous amounts of energy have been expended in efforts to control it, to no avail. ‘Wild tobacco’ is
Solanum mauritanicum
, which grows into a small tree with purple potato flowers and large grey leaves. Brown Cuckoo Doves love its heavy clusters of berries and sow them throughout the plantings in their droppings. Inkweed is
Phytolacca octandra
. Nobody knows how any of these exotics made their way to Australia. Lantana on the other hand was deliberately imported, propagated and planted for forty years. It now covers 4 million hectares in eastern Australia.

The amount of energy and ingenuity invested by the first settlers on introducing Lantana is truly amazing. They had hardly pushed a trowel into Australian soil before they were sending orders to nurserymen in London for cultivars of Lantana, the new wonder-shrub from the American tropics. William Macarthur, youngest son of pioneer settler John Macarthur, began making a garden at the family property in Camden in 1820, when he was just twenty years old. The Hackney nurserymen who supplied Macarthur began listing
Lantana camara
, one of the seven species originally named by Linnaeus, among their wares in 1825 (
Loddiges Botanical Cabinet
, 1825, No. 1171).
L. camara
appears in all the printed catalogues of Macarthur’s garden, from 1843. His 1850 catalogue lists two more, another
L. camara
, var.
crocea grandiflora
, and
L. montevidensis
, otherwise known as
L. sellowiana
, after the Prussian botanist who originally collected the seed in Montevideo in 1822. This species with purple flowers was much desired as a summer bedding plant for English planting schemes in the 1850s. At some point Macarthur acquired the West Indian species
L. trifolia
(formerly known as
Camara trifolia
) under the name of
Lantana annua
.

The passion for Lantana did not slacken; more and more cultivars were introduced, adding to the weed potential of the eventual hybrid. In 1847 Messrs Dickenson and Co., Florists of Hobart, offered
L. nivea mutabilis
, as described in Hooker’s
Botanical Magazine
(5:3110) in 1831 (
The Courier
, 4 September). In 1848 the Rev. R. R. Davies of Longford in Tasmania imported two varieties of Lantana under the names
L. drummondii
and
L. sellowii
(
The Courier
, 13 September). In November 1850 a Mr Woolley showed his version of the
L. camara
var.
crocea grandiflora
at the Australasian Botanic and Horticultural Society Summer Exhibition in Sydney (
SMH
, 30 November) and the next year saw it being regularly advertised by Sydney nurserymen. In 1851 a Surry Hills nurseryman was offering three varieties of Lantana (
SMH
, 29 April 1851). Within weeks two more Lantanas,
L. aurantica
and
L. aculeata
, were being offered at auction. By 1852
L. camara
was on show in the Sydney Botanic Garden. In 1860 Sir Daniel Cooper won the silver medal at the Autumn Exhibition of the Horticultural and Agricultural Society for a ‘new and rare’ plant reported as
L. grandiflora alba
(
SMH
, 9 February). Brisbane nurserymen began offering Lantana in June 1862; in July 1867 the garden correspondent of the
Brisbane Courier
was telling his readers that among plants that ‘are adapted to this climate and very desirable for the beauty of fragrance of their flowers’ ‘various lantanas’ were some of the best (25 July).

The invasiveness of Lantana had already been noticed. In 1864 a visitor to a property at Lake Innes, near Port Macquarie, reported that ‘The trees are getting destroyed by a shrub imported by the original proprietor for hedging, namely, the lantana; it has now grown everywhere, and covers hundreds of acres, “thick as black night”.’ (
SMH
, 1 July) Even so, still more Lantana cultivars were being imported into the colony. In 1868 Mr R. Stephen, Florist, showed ‘four varieties of lantana’, described as ‘new to the colony and worthy of cultivation’ (
SMH
, 5 November). The
Brisbane Courier
was still describing Lantana as one of ‘our best hedge plants’ in 1877 (15 October), although
L. camara
, ‘A tall rambling shrub from tropical America, used in some places for hedge making’, had been listed in a series on weeds in the same newspaper on 19 April 1873. By 1880, when Lantana was finally being described as ‘a wretched pest’, it was far too late to arrest its onward progress.

Lantana affords valuable cover not only to birds and one vulnerable species of native bee but also to small macropods and large lizards, and to possums when they are feeding on the ground. Birds, especially the tinier fairy wrens and finches, love it. The pademelons are never safer than when they are within their tunnels in the Lantana. Nevertheless, it has to go.

At CCRRS every year we remove tons of Lantana with chainsaws and brush hooks. Sometimes we use our minidigger to drag it down from steep slopes and sometimes we simply roll it over and over and leave it to rot down in a gully. The soil where it grew is always clean, friable and cool, immediately ready to plant into, once we have painted any remaining rooted canes with neat herbicide. Lantana needs sun; once our little trees are high enough to cast shade, Lantana is no threat at all. What is more, if the canopy is restored, none of the other weed species associated with Lantana will take over the space that it has vacated. The message is simple: if you want to eliminate Lantana, restore the forest. Nothing else will work.

Eliminating Lantana by shading it out is not an option for many of the managers of the 4 million hectares that it now covers in Australia, which is why it was the first plant species ever selected for biological control. The scientists could hardly have selected a more challenging candidate.

The aggregate species known as
L. camara
is a ‘variable polyploid complex of interbreeding taxa.’ It contains a wide diversity of varieties arising from horticultural and natural hybridisation, selection and somatic mutation. (Johnson, S., 9)

There are by now many biotypes of weed Lantana in Australia. What this means is that Lantana is incredibly adaptable and can cope with a vast range of cultural conditions; the dozens of insect species that were chosen as biological controls had to be specialists. Out of the twenty-six insect species released in Australia to prey on Lantana, only four are said to be reducing its vigour: the sap-sucking bug
Teleonemia scrupulosa
; the leaf-mining beetles
Uroplata girardi
, released in 1966 and 1972, and
Octotoma scabripennis
; and the seed-eating fly,
Ophiomyia lantanae
(Day
et al.
).

Attention then turned to fungus infections as a means of control. In 1999
Prospodium tuberculatum
, a fungal leaf-rust collected from Lantana in Mexico, was released in Mount Warning National Park. Most people think that biological controls are greatly to be preferred over chemical controls, but chemical controls can be targeted in a way that biological controls cannot. Though it might seem that an insect or a fungus is a specialist and will attack only the target plant, the matter cannot be proved until the agent is released in a new environment, and that might well be too late.
Teleonemia scrupulosa
attacked Lantana in its native Mexico, but in Uganda it developed a taste for sesame (Greathead). In the US it attacked plants in the genus
Diospyros
as well as Lantana (Pemberton, 492). Since the rust was released at Mount Warning in 2000, it has been released in more than a hundred locations in New South Wales. So far it has not been detected on any but the target species. Unfortunately none of the Cave Creek Lantana has shown any sign of a rust infection, possibly because the winters are just too cold for the rust spores to survive.

Tree weeds and Lantana are troublesome enough, but the soft weeds that infest the Numinbah Valley are in some ways worse. Stinking Roger (
Tagetes minuta
) comes originally from the southern half of South America, but has been spreading around the world since the Spanish Conquest. The species name ‘
minuta
’ refers to the flower; in our conditions the plant itself grows to shoulder height. It is usually accompanied by Cobblers’ Pegs, also called Farmers’ Friends (
Bidens subalternans
), now cosmopolitan, originally from tropical central America. Both weeds have allelopathic properties, which enable them to suppress competition (Lopez
et al
.). Then there is Paddy’s Lucerne (
Sida rhombifolia
), which is almost impossible to uproot. When it turned up in pasture in southern Queensland, the first observers were bemused:

It is not a foreigner, however, being indigenous to northern Australia. We know nothing of the history of its spread, which is unaccountably rapid and formidable. Why it should have existed all the years it did in north Australia, without spreading, and then to come trooping all over the land, must remain an unsolved problem. (
BC
, 4 March 1879)

The common name is an old corruption of ‘Paddy Lucerne’. It was early realised that this tough plant was a source of strong vegetable fibre, as useful potentially as jute, and specimens were sent to Europe. The plant needed to be improved and sown thick, so that it grew without branching, and then retted (soaked in soft water) like flax, to extract crude fibre for processing, but the industry never took off, partly because of a chronic shortage of labour. (Maiden, 1891)

Then there is Blue Top, ‘identified by the Government Botanist in 1924 as a South American species of heliotrope that has been naturalised in Queensland for some years past . . . A few years ago it appeared about Warwick and has established itself as a very bad weed, most difficult of eradication.’ (
Q
, 15 March) ‘Blue Top’ is not a heliotrope, but
Ageratum conyzoides
, known to English gardeners as ‘Bachelor’s Buttons’, which is so rampant in subtropical conditions as to be virtually unrecognisable. It is usually accompanied by its relatives, Mist Weed (
Ageratina riparia
) from
Central America and Crofton Weed (
Ageratina adenophora
) from Mexico. These are all handsome plants with considerable horticultural potential, but in subtropical rainforest they spring up where there is the least spill of sunlight. Creek banks are particularly vulnerable. In 1951 it was reported that Crofton Weed invasion had caused some farmers in the upper Numinbah Valley to abandon their land (
The Courier-Mail
, 22 February 1951). Even harder to eradicate is another garden escape,
Tradescantia fluminensis
, which was smothering our native groundcovers until we found a truly nasty and extremely expensive herbicide that knocks it. Amid the mess of Blue Top and Stinking Roger you will find Purple Top,
Verbena bonariensis
from Brazil, and Red Milkweed (
Asclepias curassavica
), recognised as invasive weeds as long ago as 1879. Nowadays the Red Milkweed has been eclipsed by the Balloon Milkweed (
Gomphocarpus fruticosus
). This made its initial appearance in Australia as a garden plant. As a little girl I used to pick the inflated seed capsules when they were still green, and float them in a dish of water, because with their curved stems they looked like green swans. Now I yank them out by the hundreds.