Pietermaritzburg - the weed capital of South Africa
The municipal area of Pietermaritzburg lies at the interface of several of bioresource and climate zones. The rainfall ranges from about 700 mm to over 1 300 mm per year and the soils range from shallow developing soils to deep humic soils high in organic matter. This extensive range in environmental conditions invites a wide range in suitability for plant growth and in the Ferncliffe area alone over 80 species of declared and invasive weeds have been identified.
The tragedy is that it is the watercourses in particular that are choked with alien weeds, forcing the indigenous forests to give way. The beautiful Cascades, where the Town Bush stream tumbles over a series of rocky shelves, must have been the most marvellous area of natural beauty in Pietermaritzburg.
Today it is hidden by a mass of ginger lilies, gum trees cut out the sun, and a tangled jungle of Mauritius thorn prevents access to the stream above the Cascades. One can just imagine the fun that children had in the past, playing in the stream while their parents relaxed at a picnic site nearby. What also spoils Cascades is the tarred road constructed almost on the bank of the stream.
Just how did all these weeds become such an enormous problem? Many of them were brought in as ornamental plants, some for their fruit and others as commercial timber trees. Others are reported to have come in hay which was imported for horses of the English army during the Anglo-boer war. They then thrived and seeded so well that they were able to compete with the indigenous vegetation, dominating forest verges and eventually invading into the forests. In addition they were able to thrive because they arrived here without their natural enemies. In many areas poor management of the vegetation caused it to lose vigour and create an opening for alien invaders. An example of this is what is often referred to as "cancer spots" in the veld. A single wattle tree will germinate in the veld, survive fires and grow to a size when it will produce seed. Strangely enough this happens so often. If the land owner got in timeously and hand-pulled the young tree he would have avoided a huge problem of the future. Instead the tree drops seeds annually and the single tree becomes a grove, and then a "jungle", resulting in a loss of grazing land. At this stage the landowner sees the problem as insurmountable - it will cost him two to three times the value of his land to remove the trees and rehabilitate the area effected. Anyone travelling through the midlands of KwaZulu-Natal will see how extensive this problem is. Even if the trees are removed, a threat will remain for many years - the seeds of Acacia species have been germinated after lying dormant for 45 years.
Most of the weeds which plague Pietermaritzburg and are exceptionally difficult to control, originate from central and South America. These include ageratum, bugweed, Indian canna, cat's claw creeper, lantana, sesbania and triffid weed, which are all category 1 weeds. Asia contributed a few category 1 weeds including the camphor tree, ginger lily, and the wax tree. The latter is not only invasive but can dangerously affect people who come in contact with it. Children playing with the berries and even adults chopping down trees have suffered severe allergic reactions. Yet this tree is common in Hilton where it can be seen growing out of hedges. Australia has produced long-leaved wattle and escapees from our timber plantations namely gum and wattle trees, while the Mediterranean region produced Spanish reed. One of the biggest problems of the midlands of KZN is American bramble. Other invasive weeds of the area are castor oil plant, peanut butter cassia, jacaranda, mulberry and privet, all category 2 and 3 weeds.
The threat of alien weeds was first taken seriously when it was realised the huge amounts of water that these plants utilised. It was calculated that it was cheaper and more effective to remove alien plants than it was to build dams to store water. In any case, aliens weeds in the catchment of a dam reduced the runoff which was essential for feeding water to the dam. It was found that when alien plants were removed from a catchment, streams that had not flowed for years suddenly started running. To solve this problem an organisation called Working for Water came in to being with the purpose of removing trees from key catchments. This has functioning with varying success.
Why does it appear that so little has been done to tackle the problem? For one thing the process of removing aliens and stabilising an area is very expensive and generally money is allocated to areas that are seen as more important. Then it is not only a matter of clearing the trees - the area must also be stabilised by replacing the weeds with suitable indigenous vegetation, usually a mixture of grass species. This does not mean that the problem is over. The rehabilitated area will have to be monitored and weeded regularly as there will be a long-term seed bank in the soil, and seed will be carried in by birds, the wind and other seed dispersing agents. In fact the area will have to be carefully controlled for evermore.
It is disappointing that the general public of Pietermaritzburg is so apathetic about the weed problem right on their doorsteps. Some are just not aware and an example of this is a nature reserve outside town that has a huge bugweed tree shadowing the path to their entertainment area. The Ferncliffe Catchment Conservancy (FCC) has encouraged homeowners to adopt the river reach on their boundaries with little success. This proposal will be dealt with in a subsequent article. In the Cape hacker parties are organised in many of the suburbs to control alien invader plants and in Gauteng organisations such as "Friends of Rietvlei" meet regularly to care for nature reserves and their own specific areas. Attempts have been made to stimulate the interest of residents in the northern suburbs and recently a request was made for residents to turn up to assist in the restoration of the wetland at the foot of Hawkins Road. Three committee members of the FCC turned up. Unless residents take an interest in their environment, their suburbs will continue to be a weed jungle instead of the magnificent forested area that it has the potential to be.