What does it look like?
Pampas is a perennial, tussock-like grass. There are two species present in Northland (Cortaderia jubata and Cortaderia selloana). Both have coarse abrasive leaves that are bluish green above and dark-green below, with a conspicuous midrib. It grows 2-3m high and has flowering stems, which can be up to 5m high, have distinctive, erect, fluffy white or pinky-purple flower heads. Pampas may be confused with the three native toe toe species which have more creamy-yellow flower heads. The pampas species also have dead leaf bases which spiral, resembling wood shavings.
Pampas inhabits a range of areas including dunelands, plantation forests, quarries, roadsides, and disturbed native forests. It will establish most easily in wet, sandy, bare soil. Tolerant of drought once established. In some areas of Northland infestations along the road or rail corridor are the main or only infestations.
Why is it a problem?
Pampas plants are highly competitive once seedlings are established, and can out compete native plants. Very invasive forming dense, often impenetrable, stands. Colonises and becomes dense quickly, suppressing the growth of other vegetation including groundcovers, shrubs and ferns. Often followed by weedy vines. The rapid growth and accumulation of biomass above and below ground results in a domination of light, moisture and nutrient supply. In plantation forests, much of the fertiliser applied to trees is consumed by Pampas. Also forms habitat for pests such as rats, rabbits and possums which may have a detrimental impact on surrounding vegetation.
Produces flowering stems of up to 5m in the summer period from January to March (C. jubata), and in Autumn from March to May (C. selloana). Produces a very large amount of seeds (up to 100,000 with one plant able to produce millions of seeds over 10 - 15 years) that are predominantly dispersed by wind up to 50 kilometres. Seeds do not require fertilisation, and as such all seeds produced are viable and can result in the growth of a large number of seedlings.
Establish that the species is not the native toetoe (look for erect seed heads in autumn) before attempting control.
- Dig or grub out seedlings or small plants. Chainsaw small plants and remove sizeable plants by bulldozer. Compost or leave on site to rot down. Burn or bury any flowerheads.
- Weed wipe (all year round): glyphosate (200ml/L + penetrant).
- Spray: Gallant (150ml/10l + crop oil) for most sites or glyphosate (100ml/10L + penetrant) for very dense sites. Use a marker dye to avoid wastage and a foaming agent to help prevent spray drift. Leave the plants in the ground until the roots have died off.