ENVIRONMENTAL NEWS - Easily recognised by its distinctive silvery-white feathery plumes, pampas grass is becoming increasingly invasive in George and elsewhere along the Garden Route.
“Also known as silwergras, Cortaderia selloana, this highly invasive weed thrives in damp, disturbed areas, especially along streams and rivers, but also in wetlands,” says Dr Arné Witt of the Centre for Agriculture and Biosciences International (Cabi).
Originally from South America, this grass was introduced as ornamental and for mine dump stabilisation because of its dense root system and vigorous growth.
“The weed is popular in gardens because of its tall stature and striking, feathery plumes that appear in the Western Cape from February to April. However, it has now become an ecological menace, out-competing indigenous grasses and other plants,” says Witt.
“More importantly, pampas grass also poses a significant fire risk by significantly increasing the fuel load. It is often referred to as a ‘biomass bomb’ or ‘fireball’. We already face significant risks in the Garden Route due to the proliferation of invasive wattles, pines and gums - and pampas grass amplifies that risk.”
The weed spreads rapidly through the abundance of seeds in its plumes, which are easily dispersed by the wind to areas up to 30km away. Beneath the soil, the plant extends its reach through rhizomes (underground stems) that facilitate the rapid formation of new clumps nearby.
“Property owners need to know that pampas grass is a category 1b species under the National Environmental Management: Biodiversity Act. This means that it must be removed, and failure to do so can result in prosecution. This applies to all landowners, including government institutions that are responsible for managing weeds in road reserves, one of the main pathways through which weeds are spread across the landscape.
“Autumn is a good time to tackle this plague. Residents can cut down the seed-bearing plumes (wearing masks and eyewear) before they mature and then bag and leave them to decompose in the sun, instead of dumping them at the municipal site from where the seeds can be dispersed or even germinate,” he says.
The plants can then be removed using a hoe or pick, ensuring that all rhizomes are removed to prevent regrowth. For larger invasions, it may be more cost-effective to use herbicides such as Lumberjack or Timbrel. Ideally the plants should be cut down to just above ground level and the herbicide applied to the new shoots, as a foliar application, a few weeks later. A second application may be needed.
According to Witt, it is critical that the herbicides are used as per label instructions, that users wear protective gear and that non-target impacts be reduced as much as possible by not applying them in windy conditions.
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