Tamarix aphylla [syn. T. articulata] (Salt Cedar or Athel Pine) is a tree with a thick trunk and broad crown, which may, under good conditions, reach an old age and a height of 15 m. It is the only Tamarix species that grows not loke a bush but forms a tree. The bark of the tree is brown and has deep grooves. The leaves are tiny scales that encircle the top of each node on the fine twigs. The twig appears to be divided into small internodes, which is the source for the scientific and Hebrew name of the species. This sign makes it easy to distinguish between this species and other Tamarix species, whose leaves are somewhat larger and do not encircle the node.
Tamarix aphylla blooms between July and November, mainly in August and September, with a plentiful and concentrated inflorescence. The flowers are tiny, and are arranged, as in other Tamarix species, in dense spikes at the tips of the branches. The flower has 5 small sepals and 5 white petals. There are 5 stamens, and 3 stigmata at the head of the pistil. In order to definitely differentiate between this species and other Tamarix species, which have a similar flower structure, it is necessary to examine the shape of the stamen-carrying disc under the microscope. The fruits of the Athel Pine look like red pointed cones, 5 mm long, which contain numerous tiny seeds that are dispersed by pappi that carry them in the wind. The fresh seeds germinate easily when they fall on wet soil, but if they do not reach a suitable place they lose their viability within a few weeks.
Tamarix aphylla is characteristic of sandy soils in southern Israel – in the Coastal Plain and the Negev. Its global distribution spreads over the Arabian deserts and North Africa. It has been transferred and planted also in other continents. In Australia it is called Aethel, which may be a distortion of the Hebrew name. Remains of Tamarix aphylla were found in archeological excavations as building material and as burning material beginning from the Upper Paleolithic Period, 25,000 years ago, until today. The skeleton of the Roman battery at Masada is built mainly of branches and trunks of Tamarix.
The species exhibits excellent adaptation to its conditions: The young seedling of Tamarix aphylla has 5 mm long leaves, which are arranged alternately. They are shed a few months after sprouting. Such leaves, with a special shape which appear only in the early stages, are called juvenile leaves, and are a known phenomenon in many perennial woody plants.
The mature plant has several traits that indicate adaptation to dry conditions: the thin branches contain the chlorophyll and carry out photosynthesis. The stomata are sunken within grooves along the internodes, and are thus protected from excessive water loss. Furthermore, the Tamarix aphylla, similarly to other plants of the Tamaricaceae family, such as the Reaumuria, has special glands for excretion of salt to the surface of the small green branches. These glands concentrate salts that have reached the shoot together with the water that was absorbed from the soil, and excrete them as a very concentrated basic solution. During the day the solution dries, and dry salt precipitate accumulate on the leaves. In this manner the tree gets rid of the toxic salts, which could have accumulated in the cells and harmed their viability. In areas where the water is salty, table salt (sodium chloride) comprises the main salt excreted. The salt that accumulates on the branches absorbs water during the humid nights and the resulting concentrated salt solution drips to the ground under the tree. The soil beneath the crown thus has an upper layer that is rich in salt, and most competing plants cannot germinate in it. Tamarix aphylla is unique among the Tamarix species in that in the absence of sodium salt it excretes a calcium solution. Since this solution is very basic, it absorbs carbon dioxide from the air and creates a layer of lime on the branches. This lime is not easily washed off, and it imparts the branches a light color. Another adaptation of the tree to desert conditions is by means of its root system, which can reach water stores at a great depth of many meters in sandy soil. Because of its ability to grow as a high and shade-providing tree, which can live and grow without irrigation under harsh conditions, and can also produce beams suitable for construction, the tree was chosen to be planted in the yards of the houses in Arab villages and near wells in the south of Israel. Today, remains of the trees still indicate dwelling places that existed in the past in the Judean Plain and the Northern Negev. The forestry authorities also planted Tamarix aphylla trees along roads in the south and in sandy regions. In the Arava it is used as a windbreaker. An erect variety of this species that was imported from Cyprus, but whose original origin is unknown, is planted for this purpose together with the common wild type.
The genus Tamarix contains 90 species of trees, mainly in salt marshes and deserts. It is difficult to differentiate between the species. The trees resemble coniferous trees (but are not). They have a delicate crown and are very branched. The leaves are tiny, and most of the photosynthesis is carried out in thin needle-like twigs. The root system is well developed and can extract water from a large area of soil. It also has horizontal roots that spread to a great distance and vertical roots that descend to a great depth. Many Tamarix species can utilize saline water and to grow in saline soils. In order to rid themselves of excess harmful salt in their tissues, they excrete salt from special glands in their leaves. A few species of Tamarix host aphids that secrete a sweet substance, which is identified with the manna that our forefathers ate in the desert. The wood is good for carpentry and for construction. There are 14 species in Israel, some of which are rare.
Written by Amram Eshel and Mike Livne