“Dit is die maand Oktober! Die mooiste, mooiste maand!
Dan is die dag so helder, so groen is elke aand,”

• Oktobermaand, poem by C. Louis Leipoldt

Rough translation of the above two lines by one of South Africa's foremost writers of a by-gone time: “It is the month October, the prettiest, prettiest month!

Then the day is so bright, so green every evening.”

In October we are, of course, in the maturity of spring, about to go into summer. But in Pretoria, we are in the midst of one of the greatest displays of nature's colours, thanks to the ubiquitous jacaranda tree, which lines street after street, showering its bright petals on sidewalks and roadways, bringing a lightness to every day.

There are around 55000 of these beautiful, but potentially harmful, trees in the city. They were originally brought to Pretoria in about 1888 when two trees were planted at a school in the Arcadia area of the city, and have since proliferated all over. The tree, properly known as jacaranda mimosifolia, is a native of South America, and thrives in hot and humid climates, though it is fairly drought-resistant.

The tree has been declared a Category Three invasive alien plant, which means, in terms of the Conservation of Agricultural Resources Act, No. 43 of 1983, as amended in March 2001, that it can be kept only on certain strict conditions in South Africa:

• shall not occur on any land or inland water surface other than in a biological control reserve. However, plants already in existence at the time of commencement of these regulations (March 2001) may continue to exist, provided they are not within 30 metres of the 1:50 year flood line of a river, stream, lake or other type of inland water body. In addition, the "executive officer" can impose further conditions on Category 3 plants already in existence at the time these regulations were imposed, which might include removing them if the situation demands it.

• must be controlled by the land user to curtail the spread of these plants.

• may not be planted, established, maintained, multiplied or propagated.

• may not be imported or sold.

• may not be acquired.

• can be exempted from the above regulations through written exemption from "the executive officer", provided there is a good reason for it.

The trees in Pretoria were given a special dispensation in terms of which the City was allowed to keep all the trees and replace those that, for whatever reason, were destroyed or died. The reason for this dispensation was that the trees were part of the character of the City and the City would thus lose something unique if they were all eradicated.

Jacaranda is listed as “vulnerable” on the International Union for the Conservation of Nature and Natural Resources (IUCN) Red Data list.

In Pretoria the trees have been found to be infected with a fungus causing root rot that causes the trees to wilt and eventually die.

Vuledzani Muthelo, a Masters student at the University of Pretoria, is working on genetic and taxonomic aspects of Ganoderma species, the fungus suspected of causing the root rot of the jacarandas, in South Africa.

According to the website of the University's Forestry and Biotechnology Institute, Ms Muthelo's research indicates that “G. lucidum is causing root rot disease on the Jacaranda trees. This fungus is known to be a pathogen on many tree species in the tropical and temperate regions of the world, including Africa.”

It will be rather sad if a fungus achieves what officialdom was unable to – the eradication of the lovely trees from the “Jacaranda City.”

I took the accompanying photos in a matter of hours this morning, trying to capture some of the magic brought to the City by these lovely, if somewhat dangerous trees.