Pampas grass (Cortaderia species) is as distinctive grass that has escaped from gardens and other plantings and become a major threat to native vegetation. Once established, the plant is very competitive, restricting the establishment of native trees, and can become a fire hazard and harbour vermin. Pampas grass is of greatest potential weed significance to forestry operations. Pampas grass is not considered an agricultural weed, because young plants are readily grazed by stock and it shows no ability to establish in cropping systems.
Individual plants have the ability to produce vast quantities of windborne seed – up to 100,000 per flower head – which can infest areas within a 25 km radius. In many cases, garden plants are the seed source for infestations.
The method of control for pampas grass depends on the site on which it occurs and the potential risk for causing new infestations. Permanent mechanical removal is recommended wherever possible. Grubbing of plants, particularly when small, is the best method of control in urban and bushland areas. This can be difficult with large plants because of their extensive root system and the abrasive nature of the leaves.
Control of large plants is easier and more effective if any seed heads are removed first and the plant is slashed before grubbing the crown and roots. Seed heads should be placed in a plastic bag and destroyed in an appropriate way. The best conditions for grubbing are when the soil is moist so removal is easier. The crown and roots must be completely removed from contact with the soil. Suitable disposal methods for plant material are necessary to prevent re-establishment.
Use of herbicides (low-risk areas) Only a registered herbicide used according to the direction on the label should be used to control a weed.
Smaller plants (less than 40 cm) can be controlled using a wiper applicator with the recommended herbicide. For larger plants, slash the plant to reduce the foliage, taking care to dispose of any plant material in the appropriate way to prevent re-establishment, and then spray with the recommended herbicide. Alternatively, the plant can be burnt (if local conditions allow), allowed to recover, and any new growth sprayed with the recommended herbicide. Do not spray plants stressed by drought or frost, and ensure there is thorough wetting of larger plants with the herbicide. Follow-up treatment may be required if regrowth occurs. (Source NSW DPI)