Ruin Habitat

Introduction

In the different vegetated areas we can find communities which have installed themselves where the fields under cultivation have been abandoned or at the margins of the places where men live. In these areas there are often accumulations of organic substances determining an increase of nitrates in the soil.

On the ruins and on the rubbles we can often find Ricinus communis, Nicotiana glauca and Rumex lunaria, some species of neo-tropical origin as Tropaeolum majus, prickly pears (Opuntia dillen ii, 0. ficus-barbarica) and Ageratina adenophora who have by now become naturalised not only in the archipelago of the Canary Islands, but also in great parts of the Mediterranean. Near the above mentioned communities, dominated by shrubs or under-shrubs and still in the same ecological conditions we can find coenosis dominated by perennial herbs such as Pennisetum setaceum, Psoralea bituminosa, Achyranthes and Glaucium corniculatum, species common especially by the sides of the main roads or in every kind of strongly disturbed areas. To these we can add Oxalis pes-caprae and Carpobrotus edulis, species imported by man as ornamental plants, respectively from South Africa and Central America.

Among the annual species we can list Mesembryanthemum crystal/mum and M. nodiflorum, two prostrate and succulent species that originally came from south Africa and which have become naturalised in many hot-arid regions of the globe. Both species grow in the period going from autumn to winter, creating polychromatic carpets on rocky soils next to the sea. In the abandoned cultivated fields, especially where large quantities of weed killers have not been used, we can find Fchium plantagineum, Sisymbrium officinalis, Asphodelus aestivus and Scrophularia arguta.

Ricinus Communis

(Euphorbiaceae) Higuera infernal

The "castor-oil plant" is a species belonging to the family of Euphorbiaceae, even if its appearance is completely different. This plant with herbaceous trunks can reach 12 meters in height, but generally it does not grow over 4 meters. Its palmate leaves can be up to 60 centimeters wide in diameter and their colour may vary from more or less deep green to purple. The flowers are grouped in glomerules at the end of the trunk, with female flowers at the base of the inflorescence and the male ones at the end. It is a wild plant in north-east Africa and in the Middle East, but it has spread all over the Mediterranean basin, in Europe and in the Canary Islands. Many are the cultivars created by man in order to obtain different kinds of variegations of the leaves. Ricinus communis is cultivated for the oil that can be extracted from the seeds even if their cuticle contains an extremely dangerous principle, the ricinus, which, even in small doses is considered as one of the most poisoning natural substances

Nicotiana Glauca

The "arboreal tobacco" is a plant up to 7-8 meters high with a flexuous trunk and hairless glaucous leaves with petiole. The light yellow flowers are grouped in spikes at the end of the small branches. This plant, native of South America has become naturalised in the hot-arid regions of North Africa and the Canary Islands and is strangely called the "mustard tree". Like all the species of the genus Nicotiana, it has alkaloids (the nicotine) which may make it toxic.

Rumex Lunaria

It is the only shrubby species belonging to the genus Rume which grows in the Canary Islands where it is endemic. R. lunaria is a shrub with a light coloured trunk and flexuous branches which are easily recognisable thanks to its ovate-round-shaped leaves.

Tropaeolum Maius

It is an endemic species of the island of Tenerife where it can easily be observed in the underbrushes of the thin pine forests, particularly on the western slopes of mount Teide. The yellowflowers of this creeping herbaceous plant catch the eye on the grey lava.

Opuntia Ficlis-Barbarica

(Cactaceae) Tunera

Opuntia Dillenji

(Cactaceae) Tunera

The genus Opuntia encompasses plants generally called "prickly pears". Actually, it consists of more than 200 species, all native to the American continent, from Canada to Patagonia. They are shrubs or small trees and their trunks have rounded blades which are generally flat, with leaves turned into more or less stiff thorns. Many species of the genus Opuntia are grown in the hot-arid regions all over the world and some species have many cultivars. In the hot-arid areas of the Canary Islands we can find two species of "prickly pears" but behaving as if they were part of the surrounding wild flora. They can be distinguished from each other for the stiffness of the thorns: Opunt dillenji has long and stiff thorns divided in clusters of three, while 0. ficus-barbaric has short, thin thorns divided in larger groups. When they are in bloom distinguishing them is easier because 0. dillenji has yellow flowers, while the other has reddish ones. Both are native of Mexico.

Ageratina Adenophora

This small shrub, up to one and half meters high, has flexuous trunks covered with glandular hairs. The opposite whitish leaves are ovate, pointed and generally pubescent on the lower face. The flower-heads are whitish. This plant is native of Mexico, but it has become naturalised and it behaves like the wild flora.

Pennisetum Setaceum

Along the main roads we can observe a grass, up to a meter high which is characterised by very close bushes and plumose purple pink spikes. P. setaceum is reminiscent of the high herbs of the African savannah. Thanks to its characteristics it has good value as an ornamental plant and for this reason there are several cultivars. P. setaceum is spread all over the hot African region and by now it can be considered a species that has become naturalised in the Canary Islands.

Psoralea Bituminosa

It is a herbaceous perennial plant up to a meter high, with trifoliate leaves and a petiole up to 8 centimeters long. Its dark purple flowers are grouped in hemispheric flower-heads. Even if Psoralea can be distinguished quite easily, in case of uncertainty it will be sufficient to rub it and a strong characteristic bitumen smell will come out of it.

Achyranthes Aspera

It is a small shrub, 50-80 centimeters high, with upright branches which are tetragonal in the upper part and densely pubescent with many leaves. The leaves are quite small (not more than 2,5 centimeters wide and 3,5 centimeters long) and are dark green in the upper face and whitish, owing to the close hair, in the lower one. The light pink flowers are grouped in long and narrow inflorescences, at the end of the small branches.

Eschscholzia Californica

This annual plant, tending to become perennial, is not higher than 60 centimeters. Its glaucous leaves are finely pubescent or hairless. Its flowers have four yellow or light orange petals. The fruit can be up to 8 centimeters long. This species is indigenous to California and it has been widely cultivated in every region with a hot and arid climate; in these areas it tends to become wild and intrusive. There are many cultivars of E. californica with variegated flowers changing from light yellow to white and orangy red.

Oxalis Pes-Caprae

The genus Oxalis consists of species which now can be found all over the world, even if its original areas have been identified as South Africa and South America. The "four-leafed clover of the Bermudas" has been used for long time as an ornamental plant in many regions, specially those with hot-arid climates. Oxalis pescaprae is a herbaceous plant, bulbous, with four-lobed leaf and petioles up to 12 centimeters long. The bright yellow flowers are grouped in umbelliform inflorescences with long stalks.

Carpobrotus Edulis

Also the " Hottentots' fig" is a species native of South Africa that has become naturalised in many parts of the world, especially where it can find a hot and arid season (Australia, California and South Europe). It is a creeping herbaceous plant characterised by fleshy and edible leaves. The opposite and trigonal leaves are carinate in section, thick and 8-1 2 centimeters long. The yellow-purple flowers are 5-6 centimeters in diameter.

Mesembryanthemum Crystallinum

The genus is native of Namibia, but most of the species have spread all over the world, especially in the countries next to the sea and with hot climates. The "adder's tongue" is an annual plant, with trunks creeping on the ground and ovate-spatuliform, papillate and fleshy leaves. The whitish or pinkish flowers (usually 2-3 centimeters in diameter) open only when the sun directly strikes them.

Mesembryanthemum Nodiflorum

This plant is very similar to the previous one with which it shares the same surroundings. It can be distinguished from the other thanks to its narrow leaves (2-3 millimeters thick) which are linear, semi-cylindrical and covered with larger papillae.

Echium Plantagineum

It is an annual grass, covered with blackish, strigose and glandular hairs. The leaves are complete, lanceolate or ovate and the ones at the base are larger than the cauline ones. The light blue flowers are up to 3.5 centimeters long and are arranged in branched inflorescences long and narrow. F. plantagineum is a very common plant in the agricultural areas all over southern Europe.

Sisymbrium Officinalis

It is an annual grass, up to 80 centimeters high. The upright trunk feels coarse owing to the presence of many strigose hairs which are reddish to violet in colour. The leaves are pinnate, the yellow flowers have petals not larger than 2 millimeters and are arranged in long and narrow linear inflorescences.

Scrophularia Arguta

It is an annual grass of up to 25 centimeters high and characterised by a tetragonal trunk. The ovate leaves have dentate margins. The small purple flowers are arranged in spike-like inflorescences.

Asphodelus Aestivus

The genus Asphodelus encompasses herbs with flat leaves of up to 60 centimeters long which are held in a basal rosette. When the plant is mature, the flowers are arranged on an upright small trunk (sometimes branched on the top) leading off the centre of the rosette. In this species, the caulis is strong, up to 2 meters high and the whitish flowers are sometimes numerous.