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The GREEN HORSE - sustainable horsekeeping

FEBRUARY MARCH 2010
Vol 31-5

In the Current Issue of The Green Horse you will find the following articles:

Information Exchange - Reader’s Tips, Views and Questions
Weed Watch - Lippia by Nicola Field
Compulsory Property Registration, Qld supplied by DPI, Qld
Pastures pt2: Making it Count in the Dry by Chris Ferreira
Fertility Control for Wild Horses Seminar
Growing Grains for Horses pt 1 by Andrea Carmody
Growing Equine Herbs - Rue by Cath McDowell
Snakes; Is That Poisonous? by Nicola Field
DIY Insect Repellent
Landcare Update;
Book Review
Fertilisers pt1- Biodynamic by David Mason-Jones

Weed Watch: Lippia by Nicola Field

Above: Lippia is a very hardy, invasive plant growing in dense mat-like clusters.

Like its relative Lantana, the introduction of Lippia (Phyla canescens), from South America, undoubtedly also seemed like a good idea when introduced into the country several decades ago. It was promoted as the ‘no mow’ lawn and is sometimes referred to as Condamine Couch, though it was sold in nurseries under the incorrect name of Phyla nodiflora. Today Lippia has escaped its suburban origins to become an unwanted, and extremely persistent pest, infesting millions of hectares in the Murray-Darling Basin (NSW) alone, costing large sums of revenue in affected areas. One farmer local to the Murray-Darling Basin is claiming to have lost up to $2 million in production due to invasion.

Lippia is a perennial herb with short leaves ranging from 0.5cm to 3cm in length. The plant’s tiny lilac flowers are very pretty, forming colourful clusters. However the key identifying feature of Lippia is the plant’s mat formation. From a single deep tap root it spreads out, shooting roots from stem nodes that allow the weed to spread across wide areas of ground, out-competing and smothering other plants.

Despite its attractive flowers, Lippia has plenty of ‘ugly’ features. The roots can sink metres below ground level, sucking the soil dry and cracking river banks and levees. Along with its invasiveness as it forms dense mats, Lippia is also extremely hardy with an ability to remain dormant until poor conditions improve. Along with surviving flood and frost, Lippia is often said to be the only source of greenery during periods of drought. This is because it secretes allelopathins - toxins which inhibit growth of neighbouring plants, including native vegetation.

With only limited forage value, the spread of Lippia can quickly contribute to the complete de-stocking of pasture land. Prompt action is important as eradicating Lippia becomes more expensive and time consuming over time.

Control
Lippia can be extremely difficult to control. Long term control usually requires a combination of herbicides, mechanical control and good pasture management.
Short term control of Lippia can be achieved through mechanical removal – ploughing or harrowing the ground. The seeds are easily captured and spread by machinery so it’s important that any equipment used is hosed down before leaving infected areas.
Herbicides are best applied when Lippia is actively growing, though it is worth enquiring with the local rural authority about which product to use. Some herbicides can be used to reduce Lippia without harming competing grasses, though the rapid recovery rate of the weed means several applications may be necessary for long term control. This method of control is unsuitable for use near waterways.

Prevention
To help prevent the re-establishment of Lippia, it is essential to sow infected areas with perennial pasture species. As Lippia can release allelopathins, it is recommended that the land be allowed to lie fallow for at least two to three months to allow time for toxins to disperse. Re-sown pastures should be maintained and monitored to ensure any Lippia growth is suppressed.

For more information on Perennial Pastures, refer to Volume 31, No 3, page 48 of the Green Horse.