Pampas and Purple pampas
Scientific name: Cortaderia selloana and C. jubata
- Large, stout tussock grasses up to 3 m tall
- Leaves, up to 2 m long by 2 cm wide, are rough, tough and sharp edged with a conspicuous midrib
- Tall upright, feathery flower heads on long stout stems up to 3 m for purple pampas and 5 m for pampas
- Pampas has ivory coloured flower heads while those of purple pampas are purple
- Frequently confused with the native toetoe (Austroderia spp.)
- Key differences between pampas and toetoe:
- Generally, pampas is larger and more robust than toetoe, including having larger flower heads
- Toetoe flowers in December to February, Pampas flowers in March/April
- Old dry leaves at the base of the pampas tussock are rolled (see photos), those of toetoe are not
- Toetoe have a white waxy coated leaf-base and leaves have many prominent veins.
Diagnostic differences between pampas and purple pampas
- Purple pampas have purple flowerheads when fresh, fading to dirty brown, while pampas have white or pink flowerheads
- Purple pampas flowerheads are usually held well above the leaves, while pampas flowerheads are closer to the foliage
- Purple pampas have hairy leaf bases, while pampas leaf bases are hairless.
- Both originated from central South America.
- Pampas was introduced to New Zealand in the 1920s and was widely planted as shelterbelts. In the 1950s it was used as cattle fodder.
- Purple pampas was introduced as a garden plant in the 1960s.
- Both are perennial tussock plants that grow for many years, producing copious quantities of hairy, wind-borne seed each year
- Pampas plants are either female or bisexual, with the female plants producing large amounts of seed
- All purple pampas plants are female but produce seed by a self-fertile process called apomixis, thus producing copious quantities of seed which enables it to become a serious environmental weed.
- Pampas was frequently used as a shelterbelt. However, the use for fodder was short-lived, as the tussocks had to be burned each year because only the new shoots were eaten by cattle.
- Purple pampas and some varieties of pampas were grown as garden ornamentals.
- The flower heads of pampas are frequently used in ornamental arrangements, but this has led to further distribution of seed.
- Grows especially well in disturbed areas, roadsides and broken ground
- Pampas is found throughout New Zealand. Purple pampas was limited to the northern North Island but is rapidly moving south and is now found throughout the North Island and in the north of the South Island
- Of particular concern is pampas as an invasive weed in establishing forestry plantations and in sensitive nature reserves, especially in sandy soils.
Impact on pasture
- Pampas and purple pampas do not invade good pasture but can be problematic in hill country and broken ground.
- If they establish, pampas plants are not readily grazed and can also limit access due to their size.
Impact on stock
- Generally unpalatable to livestock
- Main impact on livestock is due to its reduction of area of useful pasture grasses and legumes.
- Difficult to control once established.
Prevention and early eradication
- Be careful not to import hay from farms where the weed is prevalent and ensure contractors donâ€™t bring it onto your farm from contaminated properties
- Check fence and property boundaries as the seed can blow long distances from neighbouring land
- Removing the first few plants that appear on the farm can pay big dividends by saving on future costs. Pulling plants out and putting them in plastic bags before burning or burying first invaders is a good strategy. Take care not to let plants produce seed.
- Mob-stocking when seedlings are very small may hinder successful establishment.
- Once established grazing will have little effect as plants are unpalatable to most classes of livestock.
- Mowing small plants with a rotary slasher will allow livestock better access to useful pasture species but will not kill the pampas plants.
- Novel endophytes in ryegrass can help pastures resist weed invasion and spread
- Endophytes can allow pasture species to be more drought tolerant and resistant to insect attack. This enables sown pasture species to grow more vigorously, making it more difficult for weeds to establish.
- Ensure soil fertility levels are appropriate for good pasture grass growth as this can increase the vigour of sown pasture species and reduce weed establishment.
- Pampas is a grass species and the grass specific herbicide haloxyfop (Gallant Ultra, Ignite, etc.) gives effective control but can only be used as a spot treatment in pasture.
- Glyphosate is effective as a spot treatment.
- Note, for both these herbicides, the plants must be thoroughly wet with the spray and for large tussocks this may result in extensive overspray that may damage pasture.