Arid Habitat

Introduction

This ecosystem has developed almost evenly between the coast and the first slopes of the relieves in the islands, up to a height of 700 meters and is characterised by a hot and arid sub-desert climate with rainfalls fluctuating between 150 and 250 millimeters per year and by an annual average temperature almost always beyond 20° C. The vegetation can be compared with that of the arid areas of Sudan, Ethiopia, Arabia and Iran and is typical of the steppe in the African continent. In this area we can find open formations of succulent shrubs, divided into several communities all dominated by different species belonging to the genus Euphorbia. The most common of these is E. canariensis with the classic cactaceous habit. It is a succulent plant whose leaves have turned into small thorns arranged along the margins of the trunk which usually have quadrangular or pentagonal dissection. As there are no leaves, the photosynthetic function is carried out by the green branches and trunk; also the function of storing water is accomplished by these organs which slowly transfer the liquid during the dry periods. Very often a liana, Periploca Iaevigata, creeps on the trunks of Euphorbia canariensis.

Besides these species, this strip of vegetation is characterised also by Campy/ant/mis salsoloides, Euphorbia obtusifolia, Plocama pendula, Argyranthemum gracile, Allagopappus dichotomus, Sonchus canariensis and Kleinia nerilfolia. The last one has a habit very similar to the species belonging to the genus Euphorbia and differs, in only by the absence of the typical whitish latex. In this wide, hot and arid strip of vegetation we can also find several species belonging to the genus Euphorbia with non cactaceous habit; they are wooden plants between one and three meters high, characterised by the presence of a visible small trunk, more or less prostrate, from which a series of branches starts. These branches in turn tend to branch out in a dichotomous way. The result is a sort of small tree, with short trunk and almost round-shaped foliage - very similar to a candelabra or an umbrella with the wide part upside-down. These species and some others are the origin of some types of coenosis which have evolved due to the characteristics of the surroundings.

In the hottest and most arid parts there are coenosis with F. balsamifera. This beautiful plant forms some open coenosis where we can find other interesting plants, among which two graminaceous grasses: Tricholaena teneriffae (which can be found in Africa and in Canary Islands) and Hyparrhenia hit-ta, with a wide range including almost every tropical and subtropical area in Africa and Asia.

Euphorbia aphylla, Ceropegia dichotoma and Argyranthemum coronopifolium form communities developing on the rocky coasts where the influence of the sea can still be felt. Such coasts are called aeroaline as they are related to the aerosol transported by the marine winds.

In the Masca valley, on the northwest slopes of the island of Tenerife and at a height between 700 and 1 100 meters, communities dominated by Euphorbia atropurpurea develop with Retama raetam, Echium aculeatum and Lavandula canariensis. This Euphorbia with a candelabra shape is an endemic plant of Tenerife and it can easily be recognised from the others thanks to its purple flowers. Wild palm grove can also be found in the same strip of vegetation. Such communities are now very rare in all the islands of the archipelago, owing to the action of man which has greatly reduced the habitat suitable to the Canarian palm (Phoenix canariensis). This species prefers deep alluvial soil with a superficial water table for most of the year. The rare places where the Phoenix canariensis can be found are at the base of "barrancos" where, even during the dry season, a small amount of water is always present in the soil. The only natural populations of Phoenix canariensis are in the following places: Haria, Lanzarote; Rio Palmas, Fuertenventura; Fataga and Maspalomas, Gran Canaria; Gran Rey Valley, Canadas de Hurona, La Gomera; Masca, Tenerife; Brena Alata and La Palma. In some places where the Phoenix canariensis is present, Dracaena draco, known as the "Canaries drake", can be found wild; this species has become very rare owing to the action of man on those areas with a hot and humid micro climate. The wild palm groves with P. canariensis are a habitat of priority interest inside the European Community.

Communities of nitrophilous shrubs dominated by Launaea arborescens can be found in areas containing a certain amount of organic material. In these areas Launea arborescens can easily be observed at the sides of the main roads.
The range of this kind of vegetation is really wide, from Iran to the Canary Islandsand through the hottest parts of the Mediterranean basin. In the same places Gonospermum fruticosum, Lavandula buchii and Lavatera acerifolia can also be found. Another coenosis of this kind has developed on the slopes of the Anaga massif, in the north-east part of Tenerife, and it is dominated by Argyranthemum broussonetil, Artemisia thuscula, Lobularia canariensis, Plantago arborescens and Echturn simplex.

Euphorbia Canariensis

This is the plant which best characterises the arid and humid environment of the lowest areas in the Canary Islands. It is a small tree, up to 3-4 meters high, with succulent trunks like a cactus. The green trunk is quadrangular or pentagonal. The leaves have turned into spines of up to 5-14 millimeters long, arranged in clusters of three or four. The flowers are reddish-green. It is an endemic species of the Canaries but has become rarer in the oriental islands.

Periploca Laevigata
(Asclepiadaceae) Comical

It is a plant with a wooden base and long, narrow herbaceous sprouts creeping on other plants' trunks, in particular on F. canariensis. The opposite leaves are ovate-lanceolate, with pointed ends. The flowers are two-coloured with a purple-brown inner part and a greenish outer one.

Kleinia Neriifolia
(Compositae) Berode

It is a shrub with succulent trunk of up to a meter high. Its branches are articulated, that means that they have constrictions making them look like a row of small sausages. The leaves are arranged in clusters at the end of the branches: they are caducous, juicy, more or less lanceolate and up to 12 centimetres long. The flowers are arranged in whitish flower-head, but it is very difficult to be able to see this plant in bloom. It is an endemic plant of the archipelago

Campylanthus Salsoloides
(Scrophulariaceae) Romero marino

It is a shrub of up to 2 metres high. It has linear and succulent leaves. Its flowers vary from pink to light blue up to whitish and they are grouped in inflorescences, at times crooked. It is an endemic plant of Canary Islands.

Euphorbia Obtusifolia
(Euphorbiaceae) Tabaiba amarga

Like the other species of the genus Fuphorbia which can be observed in the most arid parts of the Canary Islands, E. obtusifolia is a small tree characterised by a short trunk and an expanded foliage, almost round-shaped, with branches ending in a cluster of leaves. It is a common plant, in particular in the hottest and most arid zone, of up to 2.5 meters high, with an upright trunk. It has linear leaves, with pointed ends of up to 7 centimeters long and not more than 6 millimeters wide. The flowers are arranged in inflorescences called ciazi with light green bracts. This species can be found in north Africa and the Canary Islands.

Plocama Pendula
(Rubiaceae) Balo

It is a small tree up to 5 metres high, characterised by a very evident small trunk and open foliage, with curved, flexible and drooping branches. The persistent light green leaves are needle-shaped and up to 5-6 centimetres long. The flowers are whitish, solitary, and they are arranged only in the terminal part of the branches. It is an endemic plant of the Canary Islands and its presence tends to get rarer when we move from the western to the eastern islands It has got an extremely dangerous latex, particularly harmful to the eyes.

Argyranthemum Gracile
(Cornpositae) Margaritas

The aspect of this Argyranthemum is very similar to the others, except for the dimensions of its needle-shaped leaves and the smaller flower-heads which are smaller. It is an endemic plant of Tenerife where it is quite common at less than 700 meters.

Allagopappus Dichotomus
(Cornpositae) Madarna

It is a shrub up to a meter high with a yellowish trunk. The lanceolate leaves have toothed margins and mucronated apices; they are viscous owing to the presence of essential oils. The flowers are grouped in yellow flower-heads, and in their turn they are grouped in clusters at the end of the branches. It is an endemic plant of Canary Islands, but it is not present in Hierro, Lanzarote and Fuertenventura

Sonchus Canariensis
(Cornpositae) Cerraja arborea

It belongs to the group of arboreous Sonchus (Dendrosonchus section) among which it reaches the largest dimensions. It is a shrub consisting of an upright axis, which can be single or with two or three ramifications, each with a rosette of leaves on its end. This rosette is similar to the one that is near to the soil in the herbaceous Sonchus. The trunk is up to 3 metres high. The pinnate and saw-toothed leaves are up to 15-20 centimetres long. The flower-heads are carried by one or more axis departing from the centre of the rosette, and each axis can carry as many as 100-150 small yellow flower-heads. It is an endemic species of Canary Islands.

Euphorbia Balsamifera
(Euphorbiaceae) Tabaiba dulce

This plant can reach as high as 2 metres and has a very strong, many branched, creeping trunk. The leaves are always carried in clusters at the end of the branches but, in this case, they are not longer than 2,5 centimeters. The inflorescences have yellowish green bracts. Apart from the Canary Islands it can also be found in north Africa and Somalia. As with the other species belonging to the Euphorbia genus, this plant produces a kind of latex which can be used to curdle milk.

Tricholaena Teneriffae
(Graminaceae) Cerillo Blanco

It is a perennial, graminaceous grass that grows to 60 centimeters high and is characterized by white, pubescent spikes. This plant can be found in Africa and the Canary Islands where it is quite common in the hottest and most arid zones.

Hyparrhenia Hirta
(Graminaceae)

The species of the genus Hyparrhenia can be found in the tropical countries of every continent, where they are part of the flora of the great savannahs. Among the species of this genus are grasses as high as 6 metres (H. cymbaria (L.) Stapf). H. Hirta is one of the smallest of this family only reaching 60 centimeters in height. It can be recognised by its violet-red leaves and spikes which are arranged at the end of the culm like the fingers of an open hand. It can be found mainly in the hottest and most arid zones. Also present in the Canary Islands are H. arrhenobasis (Hochst. ex. Steud.) Stapf, and H. hirta, yet there is still debate as to whether they are two different species.

Euphorbia Aphylla
(Euphorbiaceae) Tabaiba salvaje

It is a small shrub that grows to no higher than 50 centimeters. The trunk has very small and articulated grey-green branches, with opposite ramifications, which can be dichotomous or vertical. The thin leaves are small and precociously caduceus. It is an endemic plant of Canary Islands.

Ceropegia Dichotoma
(Asclepiadaceae) Cardoncillo

It is a small shrub with succulent trunks no higher than 60 centimeters and practically without leaves for most of the year. The trunk is greenish-grey-light brown, and smooth with some constrictions which make it look like a row of small long sausages. Clusters consisting of two to seven flowers are grouped at the end of the trunk. It is an endemic species of Tenerife.

Argyranthemum Coronopifolium
(Compositae) Margaritas

It is a creeping shrub no higher than 40-50 centimeters. The leaves are succulent, hairless, oblanceolate and dentate at their apex. The flowers are grouped in flower-heads of about 2,5 centimeters in diameter, with a yellow inner part and white-cream flowers. The flower-heads vary in number from one to eight. It is an extremely rare plant which can be only found in the Teno region in a small area between the Rocks of Fraele and Cape Bellavista on the humid basaltic flows at a height of between 50 and 200 meters. It must be considered as a vulnerable plant and it must therefore be protected.

Euphorbia Atropurpurea
(Fuphorbiaceae) Tabaiba mejorera

It is a plant which often grows to two meters in height. The glaucous leaves are oblanceolate and grouped in clusters at the apex of the branches. The flowers are arranged in wide inflorescences with intense purple-red bracts, whilst the fruits are brown or deep red. This beautiful Euphorbia can only be found in the south-west part of Tenerife, between 300 and 1 200 meters high.

Retama Raftam
(Leguminosae) Retama Blanca

This is a species which can be found both in northern Africa and the Canary Islands except for Lanzarote and Fuertenventura. It is a shrub grows up to 5 metres high, with flexible, reed like grayish-green branches and foliage characterised by the distance between the leaves. The young branches are articulate and shiny. The leaves are almost always absent and they can only be seen after a rainy season. The white flowers have a very strong, sweet honey smell and they are arranged in wide and huge inflorescences. It a plant with high decorative value and its flowers are sold at local markets.

Echium Aculeatum
(Boraginaceae) Taginaste

It is a small tree of up to 3 meters high, with a short trunk and branched, round-shaped foliage. The linear leaves tend to be carried in the highest part, next to the inflorescence. The flowers vary from pale blue to white and are grouped in small spike-like inflorescences. It is an endemic plant of the Canary Islands, but it cannot be found in Lanzarote and Fuertenventura.

Lavandula Canariensis
(Labiatae) Hierba del risco

This endemic species of the Canary Islands is a wooden based shrub with upright herbaceous branches ending in inflorescences. The opposing greyish-green leaves are pubescent, pinnate and with rounded lateral processes. The violet flowers are grouped in long and narrow spike-like branched inflorescences.

Phoenix Canariensis
(Palmae) Palma

This palm can grow up to 15 meters high and it is characterised by a cluster of leaves at the top of a straight trunk. It is practically always pruned and therefore its foliage consists of few leaves. The unpruned plants are shorter but with more leaves, sometimes as many as 60-100. The pinnate leaves are very long - up to 7 meters - with 100-150 couples of leaflets, coriaceous but flexible. These leaflets have auxiliary double series of short and very hard yellowish thorns. The flowers are small and grouped in close and branched inflorescences, up to one and half meters long; male flowers are whitish and the female ones yellowish. The fruit is similar to the date "tamanares" and is oval shaped, 1.5-2 centimeters long and with little flesh - they are edible but because they are of little value they are not picked and when they fall down they are eaten by birds mice and pigs.

The very young shoots may be eaten raw in salads. On La Gomera the local people use the "palm honey" whose production obstructs the formation of the inflorescences. It is used as an ornamental species in parks and gardens, where it gives good results. In the islands where the date palm (P dactylifera L.) is grown, hybrids between the two genuses can be found.

This plant, with the drake, can be considered the symbol of Canary Islands, even if its wild presence tends to diminish more and more.

Dracaena Draco
(Dracaenaceae) Drago

It is a tree-like plant with a wide, short and squat trunk from which a series of almost dichotomous branches grow. The leaves are grouped at the apex of these branches and they are arranged in a rosette shape. The linear grayish-green leaves are rigid and in the biggest plants up to 60 centimeters long. The small whitish flowers are arranged in a pendulous inflorescence. The orange fruits are round shaped and fleshy. It is an endemic plant of the islands of Macaronesia. There are many legends concerning the drake of the Canary Islands: in medieval books is written that the blood-red lymph - "sangre de dragon" - coming out from the trunk when the bark is cut had both healing (for ulcer and dysentery) and magic properties. Many speculations have been made concerning what age the dracaena could reach: Mr. Alexander von Humbolt, one of the first men to explore the Canary Islands, reports that a plant in the Orotava valley that was destroyed by a hurricane in 1867 was over 6,000 years old and had a circumference of 27 meters

Gonosperum Fruticosum
(Cornpositae) Corona de Ia Reina

It is another composite which can be easily recognised from Launea by its larger flower-heads (up to 5 centimetres in diameter) with vitreous squamae of the involucre and grey leaves. Gonospermurn is a shrub that grows up to one and half meters high, with pinnate leaves and yellow flower-heads. Gonospermurn fruticosurn is an endemic species of the Canary Islands.

Launaea Arborescens
(Cornpositae) Ahulaga

It is a shrub with small branches turned into thorns and up to 70 centimeters high with a few small hairless leaves, lightly lobed. The yellow flowers are grouped in small flower-heads one centimeter in diameter.

Lavandula Buchii
(Labiatae) Mato risco

It can easily be recognised both by its light blue flowers tending to violet and by its pinnate comose leaves. Such duvet gives them a peculiar grey colour and they feel cotton-like when touched. It differs from the other species of the genus Lavandula that can be found in Canary Islands both for its comose leaves and for its calyx which is longer than the bract below.

Lavatera Acerifolia
(Malvaceae) Malva Silvestre

This endemic species of the Canary Islands can be recognised from the rarer L. phoenicea Vent. (another endemic plant of Tenerife) for its darker flowers which are narrower in the basal part. It is a shrub of up to two and half meters high, with large pinnatifid leaves with irregularly toothed lobes and very long petiole. The flowers are large (up to 7-8 centimeters in diameter) and its mauve colour is darker at the base; occasionally they are whitish.

Argyranthemum Broussonetii
(Compositae) Margaritas

It is a hardy shrub up to 1,2 metres high very strong and close. Its leaves are up to 16 centimetres long, oval, abruptly pinnate, completely hairless or with only few hairs along the midrib. The flowers are grouped in flower-heads whose inner part is yellow and whose ligulate flowers are white. Argyranthemurn broussonetii is an endemic species of Tenerife.

Artemisia Thuscula
(Cornpositae) Ajenjo

It is a small shrub easily recognised because when its leaves are rubbed a strong incense smell comes out of them. It is up to one meter high and its silver grey leaves are usually flabby. The flowers are closely grouped in small, gold yellow flower-heads. Arternisia thuscula is an endemic species of the Canary Islands.

Lobularia Canariensis
(Cruciferae) Hierba de la rabia

It is a small wooden shrub endemic in Macaronesia. The colour of the petal varies from white to pink, while the sepals vary from green to reddish. Lobularia canariensis is a variable species of which many sub-species have been recognised: Lobularia canariensis subspecies canariensis, Lobularia canariensis subspecies intermedia (Webb) Borgen, Lobularia canariensis subspecies palmensis (Christ) Bergen and Lobularia canariensis subspecies microsperma Bergen. The above mentioned sub-species cannot be easily distinguished from one another and the only characters to which we can appeal are the variations in the colouring of the sepals.

Plantago Arborescens Poir
(Plantaginaceae) Pinillo

It is a small prostrate wooden shrub not higher than 60 centimeters, igneous and much branched at the base. Herbaceous sprouts start from the wooden branches and end with very close spikes consisting of tiny flowers with sepals and petals with a white border. Once they have ripened, the sepals and petals get a yellowish colour owing to the anthers. Plantago arborescens is an endemic plant of the Canary Islands.

Echium Simplex
(Boraginaceae) Arrebol

It is a giant perennial grass, sometimes biannual with short trunk and no branches. The linear-lanceolate leaves are strigous owing to the short silver hairs. They are held in a close basal rosette. The floral scape is characterised by the presence of leaves and it is up to 2 metres high. The white flowers are arranged in a spike-like inflorescence very narrow and long. It is an endemic plant of Tenerife.