Two years ago I posted an entry about the arrival of alien invasive plants in this country as a result of the seeds being brought in with the fodder required for the horses used by the British troops during the Anglo-Boer War (1899-1902). To my surprise, there have been a number of regular views since then from people wanting to know more about Khakibos, known elsewhere as Mexican Marigolds.
While my interest stems from their link to a conflict from the past that has had long-term consequences in this country, I have been intrigued by the interest shown in it as a plant in its own right. As I have mentioned before, Tagetes minuta was dubbed Khakibos (khaki bush) by the Boers in South Africa because of the khaki uniforms the British troops wore during the Anglo-Boer War – in sharp contrast to the traditional red and white uniforms worn during the earlier Anglo-Transvaal War (1880-1881). The British Army probably realised that wearing drab coloured uniforms would be a better camouflage.
Despite being regarded as invasive alien plants, these hardy weeds have been put to good use over time. Khakibos has long been used as a tick and flea repellent – I can remember besoms being made of Khakibos to sweep around the farm yard and laying Khakibos in the farmhouse before it was closed for long periods of time in order to limit the presence of fleas. It has a pleasant aroma when dried and a distinctive smell when fresh – one that takes me right back to my childhood forays into the veld.
With the development of technology and a broader understanding of the advantages of this plant, it now forms an important ingredient in many pet shampoos and other products. Having grown up in an environment where the Khakibos was simply regarded as a weed, I still find it astounding that it is actually cultivated in order to extract essential oils by means of steam distillation. According to the late Margaret Roberts, it is also useful to include Khakibos in one’s compost heap as it discourages the presence of egg-laying insects. It has also been recommended as a natural insect repellent for the vegetable garden: either growing it alongside one’s tomatoes or pumpkins, for example, or cutting it and placing it between such plants.
So, far from being an invasive alien – still detested by some – the Khakibos has turned out to be a useful plant after all!
A number of different species of Cotoneaster are grown in South African gardens, five of which have been declared as invasive aliens. Existing plants may be retained in one’s garden providing they do not grow within 30 m from the 1:50 year flood line of watercourses or wetlands, and that all reasonable steps are taken to keep the plant from spreading. They used to be popular hedging plants and we were advised to plant them as such in our Pietermaritzburg garden. They have been planted in some gardens specifically for their attractive clusters of red berries.
These trees originated from Asia and are spread by birds feeding on the berries – as we have discovered to our cost in our present garden. While this plant is a particular problem in the Western Cape, our experience is that we ignore a seedling at our peril because before long there will be a forest of fully-fledged trees. Unless removed, they can form dense stands which shade out indigenous plants. They can reduce available grazing land and, when eaten in quantity, the berries are toxic to animals.
Cape White-eyes have a predilection for the berries. Black-eyed Bulbuls, Black-headed orioles, Red-winged Starlings, Speckled Mousebirds and Olive Thrushes feast on them too.
We have severely pruned some impossibly large Cotoneaster trees and actually removed others to little avail: seedlings continue to pop up all over the garden.
The purpose of our trip to Fort Beaufort was to see the Martello Tower, which formed part of the extensive British fortifications authorised for the Eastern Cape by the then Governor of the Cape, Sir Benjamin D’Urban. The tower was constructed by the Royal Engineers in about 1844 and was manned until 1869. It is unusual for a Martello Tower to be erected so far inland, as they were more commonly used for coastal defence.
Dressed stone from local quarries as well as baked clay bricks were used for its construction. The base is 9,6 metres in diameter and the tower is 9,5 metres high. The stone walls are 1,9 metres thick. The garrison’s quarters were situated on the middle floor of the tower, with the magazine situated on the ground floor. There are four firing ports, each with a flue above it to carry away the smoke from the muzzle loaders that were in use at the time.
There is also a fire place for warmth during the winter and all the smoke from this and the weapons comes out from a chimney vent at the top of the tower.
That is where the flat gun-roof is, with a Machicouli gallery for defending the entrance from above.
The tower was originally equipped with a nine-pounder swivel gun that could traverse a 360 degree arc. A reproduction gun carriage is there to give visitors an idea of what the original looked like and a different gun is lying on the floor.
The Martello Tower was declared a national monument in 1938. It is disturbing to note that figs have got a firm hold on the walls – destruction of these is vital for the safeguarding of the masonry.
While in Fort Beaufort, we looked at the historic Victoria Bridge over the Kat River.
It is the oldest triple-arch bridge in the country. The bridge was designed by Andrew Geddes Bain and Major C.J. Selwyn and was built by the Royal Engineers in 1844. Having visited it some years earlier, I was relieved to note that several large trees that had been growing out of the stone walls have been removed in the interim.
There is a forest of alien vegetation growing on the banks below it though!
Jacaranda trees have been growing in South Africa for so long that most people regard them as being indigenous. That they are not, although the Jacaranda has been a beloved naturalised plant citizen, from the time it was introduced from South America in the early nineteenth century. Jacarandas (Jacaranda mimosifolia) have been planted by municipalities all over the country since then, thanks to their beautiful mauve flowers that more than meet the criteria for ornamental purposes. The most prolific plantings are surely in Pretoria, where it has been estimated that over 70 000 Jacarandas are growing – no wonder it is known throughout the country as Jacaranda City!
A number of these trees grew on the campus of the then University of Natal in Pietermaritzburg, covering the lawns and paths with a mauve carpet when I was a student. The trees flower from September to November – the periods differ slightly in different parts of the country. Certainly it was an urban myth in my student days that if you had not started preparing for the end-of-year examinations by the time the Jacarandas blossomed, your chances of getting a good pass were diminished. On the other hand … if a blossom fell on your head, you were bound to be fortunate in one way or another! The flowering season starts later in the Eastern Cape and so that myth would hold no water for the Rhodes University students in Grahamstown, for example.
Why then would this beautiful tree fall foul of the alien audit of my garden? Some years ago the government listed the Jacaranda as an invasive species that required eradication – can you imagine the uproar that resulted in places such as Pretoria? This is because they tend to invade river banks, rocky ridges and gorges in some parts of the country such as Limpopo, KwaZulu-Natal, Gauteng and Mpumalanga. The classification is in line with a countrywide decision to get rid of invasive aliens (this includes some species of eucalyptus as well as black wattle) in order to improve the natural supply of water from rivers and other wetlands.
A compromise was reached: although Jacarandas are still regarded as invaders, existing ones do not have to be eradicated. No further trees may be planted though and so they are no longer available at nurseries. We have some Jacaranda trees growing on the verge and in all the years we have lived here I have not found a single seedling growing in my garden. I commented last month on the exquisite carpet of mauve flowers covering the pavements and streets in the early morning. The reprieve on total eradication is appreciated.
For years now, South African gardeners have been urged to rid their gardens of invasive alien plants. Ironically, many of these plants were recommended to us as ‘fast growers’ by the local nursery when we started our first garden from scratch in Pietermaritzburg many years ago. Times have changed, along with a broader understanding of how some of the more aggressively spreading alien plants can displace our indigenous vegetation. The former tend to grow well because they are not prey to local insects or diseases.
While we can look back with satisfaction at all the indigenous trees we have planted in our present garden over the years, and having got rid of an infestation of Lantana spp. – as attractive as they are – a recent ‘audit’ shows that we still have a way to go. Many of these plants were either inherited with the garden or have arrived uninvited. In this occasional series I will highlight some of the alien visitors we still need to see the back of.
The first is an old ornamental stand-by in gardens all over the country, the hardy Sword Fern (Nephrolepsis exaltata).
Swathes of Sword Ferns have commonly been used to fill empty spaces where ‘nothing else will grow’ and have even been given pride of place in large pots to provide a flush of green on hot verandas. If you look around, many city buildings have Sword Ferns growing in neglected cracks and they feather damp patches in old walls and outbuildings. Sword Ferns have been popular because they are tough and apparently drought-resistant – qualities that have endeared them to even the most lacklustre gardeners.
The Sword Fern is an import from North and Central America, however, and is difficult to get rid of once it takes hold of one’s garden. I can attest that the small patch we inherited has spread vigorously, almost taking over the area where the infestation began and in doing so has crowded out some of the plants that were growing there. Try pulling them out and you are met with stolons and tubers that break off and get left behind to spawn another colony while your back is turned! Apart from the afore-mentioned, Sword Ferns are also spread by the dispersal of their wind-borne spores.