Lippia (Phyla canescens)

Lippia is a perennial ground cover plant. It is a serious weed of inland river systems and floodplains.

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How does this weed affect you?

Lippia is a serious environmental and pastoral weed of the inland river systems of NSW and Queensland. It is a major threat to watercourses, floodplains and pastoral areas but it is not considered a major threat to farming and cultivated lands. It is estimated 5.3 million hectares of floodplain grazing country in the Murray–Darling Basin is affected by lippia.

In Australia lippia is a major pastoral and environmental weed. It has little to no grazing value and causes major environmental impacts in terms of increasing soil erosion and decreasing stream bank stability due to loss of perennial grasses and the reduction of plant diversity. Lippia can be difficult to control as it is an aggressive plant that dominates pastures where ground cover has been reduced by overgrazing.

What does it look like?

Lippia is a prostrate perennial broadleaf herb, with numerous branched stems up to 1 m long.

It has the ability to root at nodes along the stems, providing a solid mat-like ground cover. The stout central taproot (80 cm long) has fibrous secondary roots. Fibrous roots also arise from the stem nodes.

Leaves arise in pairs from stem nodes. They are 2-5 cm long, covered in minute hairs, and have a greyish-green appearance.

Flowers appear any time from spring to autumn when soil moisture is favourable. The flowers are small, 5 - 10 mm in diameter. lilac or pinkish in colour and form a dense rounded flower.

Where is it found?

Lippia is widely distributed in tropical and subtropical areas of the world. It is believed to be native to the Americas.

In central NSW, lippia poses a major threat along the Lachlan River and floodplain system west of Forbes. Winter floods and good summer rainfall in the late 1990s resulted in the rapid spread of the weed. Lippia is now considered a major environmental threat in this area.

In southern NSW, lippia is of increasing concern on the Murrumbidgee River floodplains around Narrandera and Hay.

In northern NSW, lippia is well established in the Macquarie Marshes, throughout the lower Gwydir Valley, the lower McIntyre Valley and the Namoi Valley.

Lippia is rapidly spreading within these floodplain regions and into adjacent higher areas.

Lippia’s prostrate mat-like growth habit means that it has been used as a low-maintenance turf species in some areas. Lippia (P. canescens) has been sold incorrectly labelled as P. nodiflora.

How does it spread?

Lippia spreads both vegetatively and by seed. Plants break up during flooding and can quickly re-establish in moist soils as floodwater subsides. Fragments and seed can also be spread by vehicles, machinery and animals but most spread occurs in response to flood events.

Seed can remain viable for many years (probably well over 10) and seed banks under infestations can contain up to 10 000 seeds per square metre.

Seeds must be covered with water for a short period in order to germinate. Any area where water may sit for a week or more (including cattle hoof prints or wheel ruts) provides opportunity for lippia seed to germinate. Lippia seeds also require light and fluctuating temperatures (daily temperature fluctuations of 10 degrees or more) in order to germinate.

What type of environment does it grow in?

Lippia is well adapted to the floodplain environments of river systems in temperate to subtropical areas. The plant tolerates frost and drought and established plants can survive inundation by floodwater for at least three months. Lippia will grow in heavy clay soils, as well as lighter clays and sandy soils.

Acknowledgements

Authors: Dellow, J., Motley, K., Storrie, A., and Spenceley, J. Technical reviewers: Lester McCormick, Birgitte Verbeek, Tony Cook

References

David Illing (2000) Managing Lippia – The crucial points. Information management worksheet.

Munir A A (1993) A taxonomic revision of the Genus Phyla Lour (Verbenacae) in Australia. J Adelaide Bot. Gard. 15 (2): 109-128.

Lucy M, Powell E, McCosker R, Inglis G and Richardson R (1995) Lippia (Phyla canescens) – A review of its economic and environmental impact on the floodplain ecosystems in the Murray-Darling Basin. Queensland Government, Department of Primary Industries.

Earl J (2003) The distribution and impacts of lippia (Phyla canescens) in the Murray–Darling system. Final Report to the National Lippia Working Group October, 2003.

Crawford P et al. (2008) Lippia Management – Challenges, Opportunities and Strategies. Queensland Murray–Darling Committee (QMDC), trading as Swift NRM, for the National Lippia Working Group.

More information

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Control

Cropping enterprises

Use of herbicides, cultivation and cropping generally controls lippia infestations if the land is cropped for several years. Even in frequently flooded areas there may be an opportunity in certain seasons to crop as a ‘once-off’ strategy to suppress lippia prior to establishing a perennial grass pasture.

Due to erosion risks on floodplain soils, it is not recommended that large areas be cultivated simultaneously for lippia control. Risk of erosion can be minimised by cultivating strips across the direction of water flow. Uncultivated strips can be cultivated and sown to pasture in subsequent years.

Due to its ability to re-invade from seed and plant fragments, lippia can quickly recover from short periods of cropping, especially following floods or wet summers. Landowner experience has shown that areas cropped for 2 years can have lippia re-invade to previous levels within one wet summer if further control measures are not used.

Careful management is needed to keep lippia from invading the pasture phase of a crop rotation.

Pasture and grazing enterprises

Lippia control on arable pasture land requires an integrated approach of suppression, pasture improvement and pasture maintenance. It is a long-term program and requires dedication and continued management.

There is some evidence that lippia residues can have allelopathic (toxic) effects on establishing pastures. Where possible, it is recommended that control with herbicides be carried out to maintain a lippia-free period of several months prior to planting pastures. 

Competitive and productive pastures are an essential part of long-term control, preventing rapid re-invasion. Grazing should be managed to maintain a minimum of 70% ground cover.

Lippia suppression

Cultivation and herbicides can be used to provide short-term lippia suppression while establishing a pasture. Cultivation will often be more practical due to the variable age and moisture stress levels of the plants present. Cultivate a number of times until tareas of lippia are visibly declining.

Landholder experience has shown that cultivation of dry soil in hot weather prevents lippia fragments from transplanting and gives the best lippia kill. In northern NSW, however this is the period of highest erosion and flood risk. Blade ploughs and chisel ploughs with sweeps can give a better initial lippia kill.

With good soil moisture and actively growing lippia, applying herbicide prior to cultivation will give reliable control. Spot spraying is suitable for treating small infestations (see Chemical control below). Lippia can re-invade very quickly so regular monitoring and follow-up control is needed, especially after floods.

Managing pastures

Competitive and productive pastures are vital for long-term lippia control. Pastures that have a high percentage of ground cover prevent rapid lippia re-invasion.

In degraded native pastures, suppression of lippia can be achieved with the use of:

• selective herbicides, and
• strategic grazing to allow the better native grasses to increase in size and density (if there are sufficient numbers of productive native grass species present).

Sowing introduced pastures is generally required where lippia dominates degraded pastures.

Pasture mixtures should not be sown with a cover crop. Quick and even pasture establishment is vital. Good paddock preparation, adequate fertiliser and high grass pasture sowing rates will help to ensure adequate pasture density in the first year. High quality pasture seed is essential.

Pastures should include perennial grasses and annual legume species tolerant of waterlogging. Legume sowing time should correspond with the species and variety used.

Well-adapted perennial grasses provide good competition against lippia while the annual legumes supply nitrogen for the grasses and improve pasture quality. Phosphorus and sulfur are particularly important for good legume growth. Pasture maintenance and lippia suppression are vital to keep the pasture productive. Pastures degrade quickly if lippia is allowed to compete through over-grazing. Consult local agronomy advice when selecting pasture species for your area. 

Grazing management

As a general rule, do not graze new pasture grasses until they have become well established and are producing tillers. Sensible grazing in the establishment year can promote tillering and increased seed production.

Grazing management should always address ground cover and preferably allow grasses to flower and set seed in the first season. Recent research on grazing management of lippia-infested pastures has shown that giving the pasture periods free of grazing pressure improves pasture growth, increases the number of species present and reduces the proportion of lippia in the pasture.

Field experience also shows that grazing management needs to ensure that good ground cover is maintained when conditions favour rapid lippia growth. Good rainfall and mild to warm weather can create ideal conditions for lippia growth for up to 10 months in northern NSW. In southern NSW, lippia’s ability to grow and spread is mainly limited to the period between October and April.

Graze to maintain a pasture bulk which shades lippia and competes for moisture. If pastures become too tall and rank for grazing under good seasonal conditions, slashing will promote new growth and may provide a mulch layer which covers and impedes lippia growth. Alternatively, the tall rank pasture can be used to shade lippia and become a source of winter feed for livestock.

Biological control

Efforts are currently under way by the National Lippia Working Group based in northern NSW to investigate biological control options.

Biological control of weeds is a long-term approach often taking 10 to 30 years to achieve results. A number of pathogens and insects have already been identified that may have the potential to assist in lippia control, but the outcome will not be known for 3 to 5 years. The management techniques recommended here should not be stopped in the hope of a successful biological control agent being found.

Control on non-arable land

Options for the control of lippia on non-arable land are more limited.

Spot spraying with selective herbicides using vehicle-mounted hose-reel and hand-gun sprayers can control lippia in areas where access for cultivation is limited and cultivation is not possible.

If pasture establishment is feasible, clovers and fertiliser can be broadcast into lippia areas and may provide some extra winter and spring feed for livestock. Initial spot spraying with herbicide will provide a fallow for pasture establishment. If access is possible, small machinery can be used to direct drill perennial grasses and annual legumes. Once established the pasture will need on-going maintenance to remain productive and suppress lippia.

Herbicides

Herbicides are an important component of lippia management and should be used in conjunction with cropping, pasture improvement and grazing management where appropriate.

When seasonal conditions allow, two herbicide applications within a growing season have been shown to give significantly better control of lippia than single applications. A late spring or early summer application combined with a late summer application is recommended. Single applications can leave small amounts of viable rhizome/root tissue, allowing rapid re-infestation of treated areas. Follow up treatment when the regrowth lippia begins to flower should be made even if a high kill rate has been achieved with the first application.

Herbicide application timing is critical – herbicides should only be applied when lippia is actively growing and starting to flower prolifically.

At least 50 mm of rainfall (over one or two days) is needed before spraying to provide adequate subsoil moisture for good growth and to allow the lippia to flower. However, herbicides should not be applied within 4 days of heavy rainfall nor if heavy rainfall is forecast to prevent pollution of streams and aquatic environments with the herbicide. Generally the first application of herbicide will kill a high percentage of lippia plants. However, the small number of plants that survive need to be controlled or they will rapidly re-invade the following season.

In pastures a summer spray program will need to be repeated every 2-3 years. This interval will be dictated by seasonal conditions and pasture competitiveness. Wet summers will favour rapid lippia re-invasion, but these conditions are also ideal for achieving good lippia suppression using timely herbicide applications.

Herbicide options

See Using herbicides for more information.

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PERMIT 14197 Expires 31/07/2024
2,4-D amine 625 g/L (Various products)
Rate: 1.7–3.1 L/ha plus 1% crop oil
Comments: Spray for pastoral land. Maximum of 2 applications per growing season. Apply when in a fresh condition, mid-flower, with good soil moisture present. See permit for more critical use comments.
Withholding period: 7 days withholding for grazing
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Dichlorprop 600 g/L (Lantana 600®)
Rate: 5 mL per 1 L of water
Comments: Spot spray, knapsack rate. Completely wet plants.
Withholding period: Nil.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Dichlorprop 600 g/L (Lantana 600®)
Rate: 5.0 L/ha
Comments: Boom spray using high water volumes – minimum 100L/hectare. For best results spray at flowering.
Withholding period: Nil.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Dichlorprop 600 g/L (Lantana 600®)
Rate: 1 L of herbicide per 200 L of water
Comments: Spray application - completely wet all leaves and stems of target plants.
Withholding period: Nil.
Herbicide group: 4 (previously group I), Disruptors of plant cell growth (Auxin mimics)
Resistance risk: Moderate

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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area	Duty
All of NSW	General Biosecurity Duty All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.

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Reviewed 2024