Liz Wheeler writes:-
Over the last two or so years I had notice the occasional small pretty plant flowering during summer in the shallow parts of the Liesbeek in the Rondebosch area. This Summer past it just suddenly proliferated in size and numbers particularly at the Albion Spring reach. One gets a feel for these invasives so I decided it best be identified.
Thus learning the news above we set out to search for it. The Friends of the Liesbeek River Team therefore in January 2009 removed all plants seen from Bishopscourt (Winchester Avenue) to the N2. This does not include private property from below Paradise Park to Sans Souci Road. The island and wetland around Liesbeek Lake in Observatory still needs attention. A stable canoe or boat is needed on site as well as waders. It is very difficult to remove from amongst the reeds in wetlands. The root mass is big, wet and heavy.
I find it strange that we were not told about the plant as we gave input to the original list for the CARA regs and had we known we would not now have the problem we have especially down in the Liesbeek Lake area!
Anyone with this weed in their garden or on their private river bank is requested to please remove it immediately, bag it and notify river warden James Cooper at firstname.lastname@example.org or on 073-2700-889 He will arrange collection thereof. The River Team will help if you are unable to remove it. Again just contact James.
More about purple loosestrife
Lythrum salicaria – purple loosestrife
Category 1 – declared weed – prohibited in South Africa
An erect perennial herbaceous plant up to 2m high with showy dense spikes of rose-purple flowers. In full flower in summer.
Leaves are stalkless, lance-shaped and opposite or in whorls of three.
Mature plants can have 30 to 50 stems arising from a single root stock. (rhizome)
Roots in the substrate with most stems, leaves above the water.
Invades wetland habitats including marshes, river and stream banks and the shores of lakes and ponds. Can form dense stands in wetlands. Difficult to dig out and heavy to carry out.
Indigenous to Europe and Asia; now naturalised and invasive throughout temperate North America.
It out competes and replaces native grasses, sedges and other wetland plants. It has an extended flowering season and a single mature plant produces two to three million seeds annually.
Warning from USA – so-called sterile cultivars are highly fertile.
A biocontrol programme has been initiated in North America.
So far in South Africa only recorded in the Liesbeek.
Reference: Invasive Aquatic Plants by Lesley Henderson & Carina J Cilliers
Plant Protection Research Institute
Agricultural Research Council
For more info see the wikipedia article.