Imbricate cactus (Cylindropuntia imbricata)(Cactaceae)

The weed

South Africa has no indigenous cacti, although some of our local succulents resemble members of the Cactaceae family. Most of our cacti were introduced from South America in the early 1900s. Fortunately, most species are not invasive aliens because they need controlled conditions to germinate and survive. Those that do invade, however, cause great damage to the veld.

Once they have taken hold in an area, they are extremely difficult and expensive to control, let alone eradicate. Prickly pear, queen of  the night, torch cactus and jointed cactus are all familiar to farmers. A lesser known cactus weed is the imbricate cactus (Cylindropuntia imbricata), or devil’s rope pear. It’s an aggressive invader that often goes unnoticed in tall vegetation on river banks or hills. But it can grow quite rapidly into impenetrable thickets, with some plants reaching up to 4m in height. Its spiky joints cling to the coats of passing game, dropping off when the animals clear a fence. This helps to spread the weed.

Imbricate cactus (Cylindropuntia imbricata), also known as devil's rope pear, occurs naturally in central and northern Mexico as well as in the southern parts of the USA. It is a shrub, often tree-like, 1-4 m tall, with a short trunk and side branches arranged in whorls. The segments of the branches are dull grey-green, with prominent tubercles that give the branches the appearance of woven rope. Groups of long, stout, barbed spines which can be silver-grey, yellow, reddish or brown and have silver-grey to yellow sheaths, are scattered sparsely across the stems. The dark pink to magenta or purple-red flowers are open during the day, giving rise to spineless, yellow fruit, clustered at the end of the terminal segments. The fruits have distinct tubercles that are nearly equal in length. The fruits do not form long chains, but a secondary fruit develops occasionally from an older fruit. Despite having a large number of seeds, the fruit is hard and unpalatable and not eaten by man or beast, and seed dispersal is therefore not very effective.

Imbricate cactus was probably brought to South Africa for ornamental purposes but has escaped from rockeries and is now invading large areas of the Northern and Eastern Cape, Free State, North West, Gauteng and Limpopo Provinces. It is problematic mainly in pastures, where its vicious, barbed spines can seriously injure animals. The extraordinary ability of the weed to spread rapidly and completely take over a patch of land is cause for great concern. Imbricate cactus is also naturalized in Australia.

GEOCACHING ETIQUETTE 101 - REPLACE THE CACHE EXACTLY AS YOU FOUND IT