Contrary to its usually perceived image as a fairly barren desert
Kingdom, the south-western lowlands and mountains of Saudi Arabia
have an wide variety of flora and fauna. Beautiful flowering plants
can be seen and enjoyed, particularly following good winter rains.
Flowers are a key component of the food chain, providing food
for many insects as well as certain birds, such as the gorgeous
nectar-drinking sunbirds.
The lowland Tihama is drier and relatively poorer in vegetation
compared to the Sarawat mountains, which typically rise to an
escarpment rim elevation of 2500 m. These impressive mountains
run parallel to the Red Sea and the west-facing escarpment is
situated approximately 50-100 km from the coast, from which it
is separated by the lowland plains and hills of the coastal Tihama.
Most of the Tihama flowers are found on drought-resistant woody
shrubs and small trees. Many of these woody plants have quite
small and waxy leaves and relatively tiny flowers, both intended
to minimize the dessication effects of strong sunlight. Beautiful
flower displays can be seen when there has been enough rainfall
over the winter months.
To discourage grazing animals from browsing their foliage, the
surviving dominant plants have developed two principal types of
defence – physical and chemical. Physical defence is typified
by the lethal-looking thorns of the acacia family of trees. Nonetheless,
camels can often be seen grazing acacias, with apparent impunity.
Chemical defence against grazing occurs in those plants that contain
substances which are toxic to animals. The milkweed shrub (Calotropis
procera)and the bottle tree (Adenium obesum)are two good examples.
The milkweed is common throughout the region and is so-named as
its leaves ooze a milky sap when cut.
The spectacular bottle-tree is found especially in the southern
foothills of the Tihama. Classed as a succulent, these plants
are unmistakable from their enormous trunks. The bottle-tree reaches
a height of up to 4 m with a bulbous trunk measuring approximately
a metre in diameter. The single pink flowers produce a lovely
delicate display and form a favoured food source for nectar-drinking
Shining and Nile Valley Sunbirds.
The most attractive flowers in the Tihama are found on the Delonix
elata tree. These trees are often located on boulder outcrops,
where more water can be trapped. Their gorgeous creamy flowers
turn yellow with age and have a long flowering period in the spring
months January-April. In years of lower rainfall the trees do
not flower.
Abutilon muticus is a widespread shrub which has lovely apricot-yellow
flowers with deep crimson centres. These open from the late afternoon
into the evening, thus minimising water-loss and providing valuable
nectar for nocturnal moths.
Carulluma russeliana , a succulent with unusual looking deep purple
flowers, occurs in the Tihama foothills close to the escarpment.
Some euphorbia species are spiny succulents, which are very similar
in appearance to the cacti of the Americas. Euphorbia have a white
latex-type sap, which can be very poisonous and is also capable
of causing temporary blindness. Large euphorbia are often found
in the wadis and foothills of the southern Tihama.
Moving up into the mountains, herbaceous flowering plants can
be found, which are closely related to more temperate species.
Geranium ocellatum has beautiful magenta flowers, usually found
in late January and into February. The plant occurs on the escarpment
slope and close to the rim in damper, rocky clefts which are kept
moist by the fairly regular rainfall on the escarpment. Voracious
herds of goats have overgrazed many areas, so the herbaceous wild
flowers are now often restricted to less accessible locations.
Beautiful asphodels, such as Asphodelus aestivus, can be locally
abundant close to the escarpment rim. The terraced fields characteristic
of these mountains are rewarding places to look for these striking
plants, which are members of the lily family.
Pterocephalus pulverulentus is another attractive herb, related
to the scabious which flourishes in the mountains within the open
woodlands of juniper trees. The bladder dock(Rumex versicarius)
is a small herb with attractive red flowers which can often be
seen in roadside cuttings. Bedouin eat its leaves in salads.
As in the Tihama, woody shrubs are also widespread in the mountains.
Euryops arabiscus is a lovely yellow-flowered shrublet which has
an extended flowering period covering most of the year. There
are also attractive purple lavenders, such as Lavandula dentata,
which produce luxuriant flower displays in spring time. In May,
Rosa abyssinica can produce an attractive splash of white flowers
along the edges of terraced fields.