The Invaders The tiny flowers are usually grouped together to form rounded heads of many flowers Most of the 600 or so species of plants found on the Rock will be found on the Upper Rock, the East Side or the southern Flats. However a surprisingly large number will be found mainly in urban areas, growing from i.e. grow in the wild without the help of man. This article concerns itself with some such naturalised species. Most people are familiar with the Bermuda buttercup or Vinagrera (Oxalis pes-caprae) since this is a serious weed throughout the Rock. Much less obvious is the Creeping wood sorrel (Oxalis corniculata), which is a weed of gardens and other planted areas, but can also be found growing on pavements and roadsides in the town area. The flower is quite small, 5 to 10 mm across. Its country of origin is uncertain. The scarlet pelargonium (Pelargonium inquinans) is a well-known pot plant which is used to add colour to urban areas throughout the world. Gibraltar is no different, but here is has escaped from its original planted areas and can be seen growing wild in various places such as the Upper Rock and, in particular, the cliffs above Camp Bay and Little Bay. It is a non-invasive species and therefore poses no problems to native species. It is a native of South Africa. More problematic is the soap aloe (Aloe maculata). This grows alongside the more common Tree aloe (Aloe arborescens), and can be distinguished from the latter by the flowers which are in flat-topped clusters rather than conical ones. The leaves are green to purplishgreen, covered with pale markings, and have sharp yellow teeth along the margins. This species, which is a native of South Africa, is found mainly around the southern end of Gibraltar. Also found around Europa Point is the highly invasive purple dewplant (Disphyma crassifolium). The flowers are similar to those of the more widespread Hottentot fig, but are much smaller, up to 4.5cm across, and pale pink in colour. The leaves are also smaller, and more rounded in section. This species is native to South Africa. This species is a problem as it spreads quite readily, forming dense mats, and replacing native species. The pink houseleek (Aeonium haworthii), has established itself on the cliffs around southern parts of Gibraltar, but in particular those above Little Bay. It forms dense, rounded clumps, and produces creamy-pink flowers in dense panicles from February to April. The grey-green leaves have purple margins. It is a native of the Canary Islands. Most people are familiar with the prickly pear cactus (Opuntia ficusindica), and perhaps with another similar species, the prostrate cactus (Opuntia vulgaris), which is found mainly around Catalan Bay. One splendid specimen of a third member of the family was discovered in 2006 growing half-way up Mediterranean Steps: the red flower prickly pear (Opuntia bergeriana). Where this plant has come from is anyone’s guess, as there are none of the species growing in Gibraltar save one plant in the Alameda Botanic Gardens. This species is a native of Central America, and is spectacular when in flower. The dragon tree (Dracaena draco subsp. ajgal) can be found growing in the Alameda Botanic Gardens, the Mount Gardens, the Convent Gardens, and in a few other places around Gibraltar. This subspecies originates from northern Morocco. The fruit is eaten by the yellowlegged gulls, and the seeds dispersed in their droppings to such an extent that young trees can be seen growing all around Gibraltar, from Rock Gun to the Waterworks entrance, and around North Gorge and Buenavista. When the trunk is cut it exudes a red gum known as dragon’s blood.

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