The wild trees currently found in the Canaries can be divided into native and non-native (allochthonous) species. Native trees represent the primitive island vegetation and many are of incalculable scientific value, since they are the remains of trees that lived in southern Europe and North Africa more than 20 million years ago. Non-natives are introduced species that, when becoming established in the wild, have occupied the ecological niche of native species, in some cases coexisting with them and in others displacing them (invasive species).
Some trees have been planted for fruit production, like oranges (Citrus aurantium), mulberries (Morus), plums (Prunus domestica), almonds (Prunus dulcis) and loquats (Eriobotrya japonica). These trees include the fig (Ficus carica), which is thought to have been introduced by the Canarian natives, and the sweet chestnut (Castanea sativa), which is widely distributed and can comprise almost entire woodlands in humid zones of the montane level where the soils are sufficiently well developed. Many animals have contributed to the spread of these trees by consuming their fruit and dispersing the seeds.
Many other trees have been imported for their ornamental value. This is true of many found in urban and landscaped areas. Among these are the Chinese banyan (Ficus microcarpa), jacaranda (Jacaranda mimosifolia), magnolia (Magnolia grandiflora), cypresses (Cupressus sempervirens and C. macrocarpa), and the tree of heaven (Ailanthus altissima). Sometimes some species ‘jump’ from cultivated areas, forming stands on abandoned land, in open fields, ditches and roadsides, like the chinaberry tree (Melia azedarach), the London plane (Platanus hispanica), some tamarisks (gen. Tamarix), the black locust (Robinia pseudoacacia), the thorny locust (Gleditsia triacanthos), the Peruvian pepper (Schinus molle), and the Jerusalem thorn (Parkinsonia aculeata). Some of these ornamental trees have adapted so well to the environmental conditions on the Canary Islands that they have become very aggressive towards the local flora (invasive species), like the sweet pittosporum (Pittosporum undulatum) and the acacias (gen. Acacia). Often, species were chosen for reforesting based exclusively on their lumber potential, which is why some of them have proven inadequate for regenerating or maintaining the original ecosystems. This is the case of the eucalyptus (gen. Eucalyptus) and some foreign pines (gen. Pinus), that now form fairly important stands.
On the other hand, willows (Salix fragilis), which are associated with riverbanks and water courses, were planted mainly for their use in basket making. Certain species of eucalyptus (gen. Eucalyptus), mulberries (gen. Morus), holm oaks, English oaks and cork oaks (gen. Quercus) have benefited from plantations set up for commercial purposes or domestic use. These plants have spread from the areas forested with them and colonised other environments.
