Danube Virtual Museum

Plants

Flora of the Danube through Serbia

Although, on its way through Serbia, the Danube flows along the foot of Fruška Gora and near the southern parts of Deliblato sands, in botanical terms the most interesting and important parts are those at the beginning and the end of the Serbian part of the flow.

Along the left bank of the Danube, starting from the border with Hungary to Bogojevo, there is a large marshy-swampy area, while at the other end, there is an Iron Gate/Đerdap Gorge with a characteristic polydominant forest vegetation of relict character.

Wetland area of the Danube in Serbia, a part of a unique complex located in the neighbouring countries Hungary and Croatia as well, represents one of the last great European floodplains still existing due to the Danube and its many meanders, oxbows, backwaters, and nearby ponds. Due to the specific flora and vegetation, as well as other wildlife, this area is called: Special Nature Reserve "Upper Danube" and it has been protected by the law of the Republic of Serbia since 2001. The main reason for protection is the fact that it is remains of a once much larger area of forest, meadows, ponds and swamps, with developed groups typical of swamps and floodplain ecosystems. Even today, although to a lesser extent, through a complex system of different aquatic and wetland habitats, this area has a remarkable diversity of wildlife composed by, among other things, more than 1000 species of plants. There are still well developed wetland forests that form wood such as: Oak (Quercusrobur), White Poplar (Populusalba), Black Poplar (Populusnigra), White Willow (Salixalba), Polish Ash (Fraxinus angustifolia) and White Elm (Ulmuslaevis), as well as different types of shrubs: Dogwood (Cornus sanguinea) and Black Hawthorn (Crataegusnigra). For wetlands and wet meadows and along the edge of ponds too, there are among other herbaceous plants, several types of orchids (Genus Orchis), Greater Spearwort (Ranunculus lingua), Iris (Irisspuria), Yellow Iris (Irispseudacorus), Reed (Phragmites communis) and Cattail (Typha genus). The water surface of ponds and backwaters are adorned with many large white and yellow flowers and almost round green leaves of white (Nymphaea alba) and yellow (Nuphar luteum) lilies.

The Đerdap area, with the National Park "Iron Gate/Đerdap” on the right Serbian side, is a natural system of several gorges and canyons with high and steep sides, intersected by broad open valleys. During the Ice Age, these steep limestone cliffs were excellent protection from the impact of the significantly colder climate of surrounding areas. The fact that the Danube contained large amounts of water, which also served as a heat storage and temperature control, significantly reduced the local adverse effects of a severe glacial climate. For this reason, Iron Gate is the largest European refugium (shelter), with plants from the Tertiary – a period that preceded the Ice Age, largely preserved to this day, as well as a type of forest vegetation typical of that warm ancient geological period.

Polydominant forests, well-developed even today, testify to the constant favourable climatic conditions of the region. These thermophilic forests of relict age resemble forests typical for tropical and subtropical regions due to the face that they produce a large number of tree species equally present, as well as the number and distribution of shrubs, creepers and herbaceous plants. Iron Gate Polydominant forests consist mainly of wood that are Tertiary relicts: Walnut (Juglans regia), Turkish Hazel (Corylus colurna), Common Hazel (Corylus avellana), Nettle Tree (Celtis australis), Black Ash (Fraxinus ornus) and shrubs: Lilac (Syringa vulgaris) and Smoke Tree (Cotinus coggigrya).
Besides the native species of plants, on the banks of the Danube, its natural backwaters and dug canals, there are also so-called adventive plants, which have been brought here from remote parts of the world usually by unconscious and inadvertent human assistance. These are primarily American species, such as low tree called Maple Ash (Acer negundo) and False Indigo Bush (Amorphafruticosa); herbaceous plants, Evening Primrose (Oenotherabiennis) and Goldenrod (Solidago serotina).

White Willow (Salix alba)

This is a deciduous tree up to 25 (30) metres tall with broad crown, brown-grey furrowed bark and branches with ends bent down.

The leaves are alternately arranged with short handles, lanceolate or broad lanceolate, pointed in the base and on a tip and finely serrated on the edge. The leaves are 4-10 cm long and about 1.5 cm wide, dark green on the face and bright, while on the reverse side they are covered with thick soft whitish hairs. Flowers are monoeciuos (male or female), grouped in separate inflorescences, erect catkins that develop on separate individuals (dioecious species). Grown in valleys of the rivers, floodplain areas, marshes and swamps, White Willow form pure groups or grow with other woody species in wetlands.

Barks of several close relatives of white willow (Salix purpurea, Salix fragilis, Salix daphnoides) are used for medical purposes because of their high level (up to 7%) of phenolic glycosides, also known as salicin. In the nineteenth century, it was especially valued as a raw material for obtaining salicin – with primary antipyretic and antirheumatic effects. However, it lost its importrance in medical therapy after the industrial production of synthetic salicylic acid and its derivatives, acetylsalicylic acid and metilsalicilata began.

White Willow bark contains less than 1% salicin and it is not used as a raw material for obtaining this substance, but it is a part of tea mixtures and other products used to reduce fever, headache and rheumatic pain.

Nettle, hackberry (Celtis australis)

Iron Gate/Đеrdаp Gorge, East Serbia

This is a deciduous tree growing up to 20 m tall with a high crown. The trunk is smooth and grey even in old age. Leaves are elongated and ovoid, pointed at the top and serrated on the edges. They are 4-15 (20) cm long and 6 cm wide. Flowers are monoecious (male) and dioecious, grouped in a cluster, although the dioecious appear individually in the axils of leaves. Dioecious flowers bloom at the top of the pole, while monoecious at the lower pole. The fruit is a small rounded stone fruit up to 1 cm wide, and is reddish and edible with a sweetish taste.

The plant of Mediterranean origin is a tertiary relict and to date has also survived in some continental habitats such as the Iron Gate/ Đеrdаp Gorge where, together with walnut, make forests. It also grows in Northeast Africa, the Iberian Peninsula, and the Apennine Peninsula, Sicily and in the Mediterranean parts of the Balkan Peninsula, as well as in northern and southern Asia Minor.

The Hackberry tree is heavy, hard, and very tough. It is resilient and very durable, used in cart construction and carving, as well as the making of musical instruments, agricultural tools and sports equipment. It is successfully grown as an ornamental tree in parks and alleys.

Turkish Hazel (Corylus colurna)

Iron Gate/Đеrdаp Gorge, East Serbia

This is a deciduous tree 25 to 35 m tall with large broad rounded crown. Its leaves are broadly ovoid or nearly round, coarsely double serrated on the edges. The leaves have a heart-shaped babe and are 6-15 cm long and 5-13 cm wide. Flowers are monoecious, the male grouped in single-sex catkins, while the female make a very small inflorescence and are largely concealed in the buds with a tuft of red columns of the pistil.

The fruit, known as the hazelnut, is edible and very tasty, although smaller than that of ordinary hazel. It is egg-shaped, widest in the middle or lower part, light brownish/yellowish, 17-20 mm long, surrounded by a thick, softly spiny and bristly involucres (husk).

Turkish hazel is a relic of the Tertiary, widespread in the Balkan Peninsula in the past. Today in Serbia it grows in the Iron Gate/Đеrdаp region and the surrounding area creating mixed forests. It also grows in South-Eastern and Western Serbia.

The Turkish hazel tree is tough and strong, with a very beautiful pink nuance. It is therefore used for making furniture, veneer lathes and a variety of products. It is planted in certain areas as a wind protection, but also as an ornamental tree in alleys, parks and gardens.

Маklеn Тvrdsk (Acer Intermedium)

Iron Gate/Đеrdаp Gorge, East Serbia

This is a deciduous tree up to 12 metres that can reach the age of one hundred years. The leaves are palmate veined and pentamerous, with three broad veins clearly visible, each leading to a lobe, serrated shallowly on the edge. The leaves are long and 3-9 cm wide and slightly leathery. The flowers are grouped in pendulous inflorescences. The fruit consists of two seeds, each with a wing used to carry the seed on the wind.

Besides in the Iron Gate/Đerdap area, this species grows in Serbia on almost all of the limestone mountain ranges, especially successful in the massifs in Eastern Serbia (Rtanj, Svrljiške Mountains, Suva Mountain, Stara Mountain). The Iron Gate/ Đerdap area is the northern limit of distribution of this species, which normally grows only in the Balkan Peninsula.


Walnut (Juglans regia)

Iron Gate/Đеrdаp Gorge, East Serbia

This is a deciduous tree up to 25 m tall, with a rich crown. Its leaves are very large, up to 30 cm long, having odd-pinnate with (3) 5–9 (11) leaflets, and a characteristic odor of iodine. The flowers are monoecious (male) grouped in drooping catkins 5-10 (15) cm long, while female flowers are grouped in clusters of two to five. The fruit is a nut 3-6 cm long, hard and wrinkled, completely wrapped in ripening fleshy green protective husk.

This tertiary relic in Serbia grows naturally in ravines and canyons in the area Đerdap, Stara Mountain, Suva Mountain, in the Pčinja River Gorge near Vranje, as well as on the right bank of the Drina River from Bajina Basta to Mali Zvornik and Bаnja Kоvilјаča. Because of the delicious and nutritious fruits rich in oil used in cooking, medicine and cosmetics, as well as high-quality hardwood widely used in the making of furniture, flooring, musical instruments, wooden parts of airplanes, cars and weapons, it is widely grown, especially in areas with oak trees.

In Asia and Southeast Europe the walnut was grown as early as 4000 years BC. Due to such long domestication, as well as the ability to expand spontaneously from where it is planted, it is difficult to determine which parts of the general distribution of contemporary walnut occurred naturally, and which under the human influence. Nevertheless, the walnut is now widespread in the nature from the Balkan Peninsula to the east - the Himalayas and Southwestern China.

Yew (Taxus baccata)

Iron Gate/Đеrdаp Gorge, East Serbia

This is an evergreen tree that can grow up to 20 m in height. Even though it is relatively slow growing, the yew can be very long-lived (about 2000 years). The leaves are needles, hard and leathery, dark green and about 3 cm long and 3mm wide. The plant is dioecious, which means that male embryos and semen strobilusi form on different individuals. On so-called female plants, after the pollination, a seed is developed, partly surrounded by a soft, bright red berry-like structure called an aril. In addition to protecting the seed to maturation, aril has an important role in its dissemination. Juicy and sweet aril is the only part of the plant that is not poisonous, and the birds often feed on it. Seeds and other parts of the yew contain a poisonous alkaloid thaksin. Although the birds take the seeds, it just passes undigested through the intestinal tract and ends undamaged in their droppings.

Besides the Đerdap area, in Serbia the yew grows on the mountains Kopaonik, Zlatibor and Goč.

Because it is a very slow-growing tree, the yew is not used for afforestation, but is often grown as an ornamental park tree.

Lilac (Syringa vulgaris)

Iron Gate/Đеrdаp Gorge, East Serbia

This is a deciduous shrub or a low tree growing to 7 m high. The leaves are arranged in opposite pairs, simple, oval to cordate, pointed at the top, with an entire margin, 5-12 cm long, 4-8 cm wide. Its flowers are dioecious, small, lilac, with a very nice smell, grouped by 100-400 in large (10-20 cm long) pyramidal panicles. The fruit is a small brown shiny capsule.

Lilac is a tertiary relic that on warm sunny rocky habitats grows naturally in the Balkan Peninsula, in western Ukraine, Romania and Hungary. In Serbia, it is widespread in the hilly and mountainous areas, such as the Iron Gate/Đеrdаp Gorge area and Suva Mountain area, where it mostly grows on limestone rocks.

Because of its decorative and aromatic flowers, it is widely cultivated as an ornamental plant – almost 350 varieties that differ in color (white, purple), shades (from light to dark purple), flowers, body ("doubled") and intensity of smell. Essential oils from the flowers are used in the cosmetic industry, while a tree, that is hard, solid and lilac-brownish color, is used in turnery.

Literature

Flоrа Srbiје 1, Srpskа аkаdеmiја nаukа i umеtnоsti, Bеоgrаd, 1992; Flоrа Srbiје 2, Srpskа аkаdеmiја nаukа i umеtnоsti, Bеоgrаd, 2012; Flоrа Srbiје 3, Srpskа аkаdеmiја nаukа i umеtnоsti, Bеоgrаd, 1972; Flоrа Srbiје 5, Srpskа аkаdеmiја nаukа i umеtnоsti, Bеоgrаd, 1973;

(Text: Natural History Museum in Belgrade)