Fifteenth Australian Weeds Conference

The problem with montevidensis ( creeping lantana)

Stephen. B. Johnson and Sydney D. Lisle New South Wales Department of Primary Industries, Locked Bag 21, Orange, New South Wales 2800, Australia

Summary This paper reviews what is known about (Everist 1981, Webb et al. 1988, Day et al. 2003, van the biology, distribution and management of Lantana Oosterhout 2004). montevidensis (creeping lantana). This information is Both naturalised and ornamental varieties of L. used to recommend an appropriate legislative response montevidensis are widely used in landscape design, for this species in New South Wales (NSW). especially beside roads and footpaths as colourful, Two species of Lantana have naturalised in Aus- low maintenance, drought tolerant plantings, and in tralia, these being L. camara and L. montevidensis. public and private gardens (Everist 1981, Webb et al. There is at least one weedy and several ornamental 1988, Neal 1999, van Oosterhout 2004). In contrast, L. varieties of the latter. Species and hybrids of Lantana montevidensis has infested hundreds of thousands of hybridise freely and many are used in horticulture. hectares of pasture land in central Queensland (Qld), Despite claims to the contrary, all varieties and hybrids and this has resulted in significant land devaluation of Lantana species are fertile to some extent. and loss of income (Neal 1999). The species is increas- Although L. montevidensis has spread extensively ingly weedy in degraded grasslands, woodlands and in eastern Australia, further spread is likely. Flowering sclerophyll forests, on alluvial plains, roadside cut- and fruit set may occur all year, with fruit dispersal tings, along fence lines and riverbanks and on rocky by a range of birds and animals, and vegetative spread outcrops (Munir 1996, O’Donnell and Panetta 2000, also possible. Lantana montevidensis forms dense low J. Hosking pers. comm.). growing thickets, invading pastures and many natural This paper summarises what is known about the ecosystems. Management is difficult and integrated lifecycle, dispersal and distribution of L. monteviden- control is needed including preventative, chemical and sis. It then examines issues surrounding the hybridi- mechanical measures. Fire, hand removal and vegeta- sation and sale of the species before examining the tion management are also useful tools. integrated weed management and legislative responses The declaration of L. camara as a WoNS species needed. has resulted in its removal from trade and distribution. However, the legislative response to L. montevidensis LIFECYCLE has been limited. This is despite the apparent potential Seeds of L. montevidensis germinate at any time of the for the species to spread further and to cross with other year provided that there is sufficient soil moisture and varieties and hybrids to form new Lantana species light (O’Donnell and Panetta 2000, O’Donnell 2002). aggregates that may hamper future control measures. Seed that was buried at 1–2 cm did not germinate. The NSW government has declared all Lantana spe- Germination flushes occurred when good soil moisture cies under the Noxious Weeds Act 1993 to help prevent conditions coincided with cold night temperatures species contributing further genetic material to the close to or below freezing (O’Donnell 2002). That au- existing pool. thor also found that smoke for 5–15 minutes stimulated Keywords Biology, lifecycle, hybridisation, germination 6–15 fold. Germination and subsequent management, legislation. growth was enhanced in pasture gaps ranging from 5–40 cm (O’Donnell 2002). INTRODUCTION Early growth of L. montevidensis is slow while Lantana montevidensis (Spreng.) Briq. (creeping the taproot and lateral roots are developed (O’Donnell lantana) is one of two Lantana species that have natu- 2002). Furthermore, mortality of L. montevidensis ralised in New South Wales (NSW), the other being the seedlings was caused by a wide range of factors species aggregate L. camara L. Lantana montevidensis including moisture stress, physical disturbance, fire, is a creeping perennial species that roots at the stem herbicides, cattle trampling, and perhaps grazing. nodes and produces low growing but dense thickets. Consequently, seedlings established more readily in Originating from South America, the species has been protected areas such as stony outcrops and areas pro- widely planted as an ornamental or has naturalised in tected from cattle, underneath fences and fallen timber, various parts of the world including Australia, New within tussocks of grasses that were not eaten and in Zealand, Africa, parts of India and North America pastures that were not subject to hot fires.

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Although glasshouse of L. montevidensis Lantana montevidensis is able to reproduce veg- have been shown to produce seeds within a year etatively, by layering (rooting at the stem nodes when (Neal 1999, O’Donnell 2002), seedling development these are covered by moist leaf litter or soil), and is much slower in the field with growth rates of 1 cm when the leaves propagate new plants (Parsons and per month (Parsons and Cuthbertson 2001, O’Donnell Cuthbertson 2001). This occurs in both ornamental 2002). Seedlings become winter dormant, reshoot and and weedy varieties (Neal 1999). O’Donnell (2002) flower in spring of the following year. suggested that plants of L. montevidensis may live for Established plants of L. montevidensis flower most at least five years. of the year in Australia and New Zealand (Webb et al. 1988, Conn 1992, Parsons and Cuthbertson 2001). DISPERSAL More specifically, O’Donnell (2002) recorded that L. Both O’Donnell and Panetta (2000) and Parsons and montevidensis flowered in response to rainfall with Cuthbertson (2001) noted that seeds are widely spread heaviest flowering after a protracted dry period, for by fruit-eating animals and birds, by water flowing example after the first spring rainfall break. across the soil, especially after heavy rain and in mud Plants of L. montevidensis are able to set fruit attached to hooves, boots and machinery. O’Donnell throughout the year, generally from early summer (2002) also noted that because seeds float, gullies and through to mid-winter in Qld (O’Donnell 2002). Seed watercourses were susceptible to infestation. Initial production in L. montevidensis generally occurs five infestations from birds were common under nesting weeks after flowering (O’Donnell 2002). Various au- and roosting sites, especially around trees and fences thors including Henderson (1969) stated that weedy (O’Donnell 2002). O’Donnell (2002) further indicated varieties of L. montevidensis produce a large amount that ants transport and bury L. montevidensis seeds of fertile seed. For example, O’Donnell (2002) found in their nests. Lantana montevidensis is also spread yearly seed production varied between 4965–5175 when viable seeds pass through the digestive tracts of seeds m-2 and while each drupe had two seeds, gener- grazing cattle (O’Donnell 2002). ally only 30% of drupes produced two seedlings. The size and density of existing colonies increases Henderson (1969) and Webb et al. (1988) recorded as stems root at the nodes and as seedlings develop that ornamental varieties of L. montevidensis did not within and near existing thickets. New plants arise produce fruit in Australia and New Zealand respec- from garden waste containing material of L. mon- tively. In contrast, Neal (1999) demonstrated that tevidensis stem cuttings and leaves when this is not 0.42–1% of florets of the purple flowering ornamental disposed of properly (Neal 1999). The trade of nursery variety examined produced fruit. These populations plants has, and continues to be responsible for the were generally in close proximity to weedy populations dispersal of this species. of L. camara and/or L. montevidensis. O’Donnell and Panetta (2000) indicated that CURRENT AND POTENTIAL DISTRIBUTION the viability of L. montevidensis seeds decreased to Varieties of L. montevidensis are widely planted as between 30–44% after one year of burial at 1–2 cm ornamentals throughout Australia. Naturalised popu- of depth while those planted near the soil surface had lations of the species are generally found in eastern only 10–18% viability after a similar time. O’Donnell coastal and subcoastal areas of Australia, from Nowra (2002) added that all surface sown seed was dead after 34°53'S in southern NSW to Cairns 16°55'S in north- two years. These results indicated that the seed of L. ern Qld (Munir 1996, Neal 1999). montevidensis is relatively short lived in the soil. In Lantana montevidensis is common in south-east addition, the seed pulp or mesocarp inhibited seed Qld, mainly from Rockhampton to the NSW/Qld bor- germination up to 100 days after sowing, but had no der, particularly in the Moreton, Wide Bay, Burnett and impact after one year, probably as a result of natural Port Curtis pastoral districts (Everist 1981, O’Donnell decay (O’Donnell and Panetta 2000). Those authors et al. 1999, O’Donnell 2002). Naturalisation has also showed that a proportion of seeds would germinate occurred in the coastal districts of South Kennedy, with the pulp surrounding them. North Kennedy (around Townsville) and Cook (around Henderson (1969) recorded pollen viability of Cairns), and the inland district of Leichhardt (Munir approximately 65% in contrast to an ornamental form 1996). examined with less than 6% viability. Similarly, Neal The species can be found on the north and central (1999) indicated 82% pollen viability from weedy coast of NSW around Casino, Murwillumbah, Byron varieties of L. montevidensis and 14–16% from popu- Bay and north from Sydney (Everist 1981, Conn 1992, lations of two ornamental L. montevidensis varieties. O’Donnell 2002). The species is also found on the The implications of this are discussed later. north-western slopes around Tamworth (Conn 1992).

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It has naturalised in Darwin (Jeffrey and Ready 1999), Cuthbertson (2001) and O’Donnell (2002). Kununurra and in parts of Victoria (Conn 1999). Neal (1999) indicated that L. montevidensis is in Prevention Strategic control of existing infestations the early stages of spread in Australia with CLIMEX and removal of the species from sale will help prevent predictions of at least 30% of Qld and 10% of NSW further spread. Hygiene practices such as fodder and at threat of serious invasion. Furthermore, O’Donnell feeding site inspection, quarantine of grazing animals (2002) noted that, since weedy and ornamental before removal, vehicle cleaning and buffer strips varieties of L. montevidensis have similar climatic between infested and clean areas will help prevent preferences, the weedy variety of the species could spread. be expected to spread beyond its present range in Australia. In particular, further expansion could occur Herbicides Fluroxypyr gave the best overall control in coastal and inland plain areas of southern NSW and of L. montevidensis while glyphosate gave good results Victoria as the species appears to be more tolerant of in autumn, but not spring. Wetting agents did not im- colder temperatures than L. camara (Webb et al. 1988). prove the efficacy of either herbicide. Dichlorprop, However, it is important to note that the ecological 2,4-D and picloram/2,4-D mixtures were less effective. limitations of the species are not known and require No herbicide achieves 100% control, with regrowth further research. from apparently dead plants after periods of two years and more. Repeated herbicide applications on actively HYBRIDISATION AND CONTINUED SALE growing plants in late summer and autumn should be × L. montevidensis hybrids have been used where cultivation is not practical. developed for use in horticulture (Howard 1969). In particular, L. montevidensis is commonly used to Physical removal Bulldozing to a depth of 15 cm achieve new horticultural varieties with low, mounding gave reasonable control of L. montevidensis. Offset and trailing growth habits. A number of authors have discs rather than chisel ploughs are also effective but noted the hybridisation of both previously geographi- multiple passes may be needed. Chisel ploughing cally separated species and varieties when grown in caused fragmentation of L. montevidensis material the same location (e.g. Day et al. 2003). with an increase in numbers resulting. Small Although ornamental varieties of L. monteviden- infestations of the weed can be removed by physically sis are often sold as ‘sterile’, this claim is incorrect. digging up and removing plants. Along with fertile pollen, Neal (1999) found up to 1% seed production in such varieties and that pollen Fire Burning trials indicated that surface seed is from weedy varieties of L. montevidensis, also often killed by hot pasture fires but buried seed (especially planted for ornamental purposes, resulted in up to 6% in ant nests) escapes. Seed that escapes a fire is more seed production in adjacent plantings of L. camara likely to germinate via smoke stimuli but these hybrids. seedlings are easily controlled by herbicides and/or The continued sale of L. montevidensis varieties trampling. Adult plants are not killed by fire because and hybrids therefore poses a quantified risk of gene regrowth occurs soon after, and while seed set may be flow in the environment. It is important to restrict this delayed, observations suggest higher flower and seed to prevent future hybrid varieties spreading to new numbers on previously burnt plants. Regrowth from environments and to make control using herbicides a burning event did not improve the performance of and biological agents less difficult (van Oosterhout herbicides over unburnt areas. 2004). Grazing management and revegetation A vigorous INTEGRATED WEED MANAGEMENT pasture sward will help prevent seedling establishment Although adult plants of L. montevidensis are very and growth. Subsequent to mechanical disturbance, resilient to fire, drought, mechanical disturbance and planting competitive pasture grasses such as Both- some herbicides through a large lignified taproot, an riochloa pertusa (L.) A.Camus (Indian bluegrass) integrated weed management program for L. monte- and Digitaria eriantha Steud. (woolly finger grass) vidensis using the measures outlined below can be and legume species like Chamaecrista rotundifolia successful. Since infestations of L. montevidensis often (Pers.) Greene (wynn cassia) will provide good occur in inaccessible terrain, limited weed manage- pasture biomass and some suppression of the weed. ment options may be available (O’Donnell 2002). The Since light appears to be required for L. montevidensis following has been extracted from O’Donnell et al. germination, seed burial via ploughing should also (1999), O’Donnell and Panetta (2000), Parsons and reduce emergence.

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LEGISLATION Contributions from the Queensland Herbarium The NSW state government has banned the sale of all 3, 1-4. Lantana species as Class 5 weeds under the Noxious Howard, R.A. (1969). A check list of cultivar names Weeds Act 1993. In addition, active management of used in the genus Lantana. Arnoldia 29, 73-109. the genera is required under Class 3 and 4 declara- Jeffrey, P. and Ready, J. (1999). Weed management tions in many coastal local control areas. This decision – planning and implementation. Proceedings of considers: the 12th Australian Weeds Conference, eds A.C. 1. That some Lantana species and all varieties have Bishop, A. Boersma and C.D. Barnes, pp. 86-90. diverse genetic backgrounds (e.g. Day et al. (Tasmanian Weed Society, Hobart). 2003); Munir, A.A. (1996). A taxonomic review of Lantana 2. That considerable potential for hybridisation exists camara L. and L. montevidensis (Spreng.) Briq. (e.g. Neal 1999); () in Australia. Journal of the Adelaide 3. That further spread of L. montevidensis is likely Botanic Gardens 17, 1-27. and the negative impacts this may have; Neal, J. (1999). Assessing the sterility of ornamental 4. The difficulties in determining correct species lantana varieties. Are we exacerbating the weed and hybrid genetic composition making legislative problem? Honours thesis, University of Queens- control of named varieties more difficult e.g. at the land. time of writing there is only one named variety of O’Donnell, C. (2002). ‘The creeping lantana handbook. Lantana registered under the Plant Breeders Act A guide to ecology, control and management’. 1994 this being a variety of L. montevidensis called (Queensland Department of Primary Industries, ‘Monswee’ (synonym L. sellowiana Link & Otto) Natural Resources and Mines, Brisbane). (COA 2005); O’Donnell, C. and Panetta, D. (2000). Creeping 5. That there is potential for mislabelling and con- lantana – an update on selected research ac- tinued sale without a blanket genus ban; and tivities. Proceedings of the 6th Queensland Weed 6. To reinforce community understanding that all Symposium, pp. 117-21. (The Weed Society of Lantana species are significant weeds. Queensland, Brisbane). O’Donnell, C., Panetta, D. and Francis, P. (1999). REFERENCES Control of creeping lantana with competitive COA, Commonwealth of Australia (2005). Plant pastures. Proceedings of the 12th Australian Weeds breeders rights. Online at www.ipaustralia.gov. Conference, eds A.C. Bishop, A. Boersma and au/pbr/. Accessed 11 April 2006. C.D. Barnes, pp. 514. (Tasmanian Weed Society, Conn, B.J. (1992). Verbenaceae. In ‘Flora of New Hobart). South Wales, Volume 3’, ed. G.J. Harden. (New Parsons, W.T. and Cuthbertson, E.G. (2001). ‘Noxious South Wales University Press, Kensington). weeds of Australia’, 2nd edition. (CSIRO Publish- Conn, B.J. (1999). Verbenaceae. In ‘Flora of Victoria ing, Melbourne). Volume 4’, eds N.G. Walsh and T.J. Entwisle. van Oosterhout, E. (2004). ‘Lantana control manual. (Inkata Press, Melbourne). Current management and control options for lan- Day, M.D., Wiley, C.J., Playford, J. and Zalucki, M.P. tana (Lantana camara) in Australia’. (Queensland (2003). ‘Lantana: current management status and Department of Natural Resources, Mines and future prospects’. (Australian Centre for Interna- Energy, Brisbane). tional Research, Canberra). Webb, C.J., Sykes, W.R. and Garnock-Jones, P.J. Everist, S.L. (1981). ‘Poisonous plants of Australia’, (1988). ‘Flora of New Zealand. Volume IV. Natu- 2nd edition. (Angus and Robertson, Sydney). ralised Pteridophytes, Gymnosperms and Dicoty- Henderson, R.J.F. (1969). A cytological study of Lan- ledons’. (Department of Scientific and Industrial tana montevidensis (Spreng.) Briq. in Queensland. Research, Christchurch).

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