Ash-tree (Fraxinus excelsior) – Fraxinus excelsior, Fraxinus ornus, Ash-tree, Ordinary Fraxinus excelsior from the Oleaceae family. Its area of distribution is in broad-leaved forests, mainly in foothills and mountains up to 1200 metres altitude throughout Bulgaria. It grows upon moist soils which are rich in minerals. Fraxinus excelsior is a broad-leaved tree which reaches a height up to 40 metres, it has a grey-brown or grey bark. Younger twigs are light grey in colour with a greenish shade. The leaves are old-pinnate, large, with a petiole, without stipules, heavily runcinate, mucronated to the tip, intact to the base, dark green above and light green below. The blossoms are gathered in panicle flowerheads, they come out of the axils of last year’s leaves and grow before the tree comes into leaves. The blossoms are synoecious – both the male and female blossoms neither have a chalice nor corolla. The fruits are an elongated winged seed and are often retained in the crown even during winter and they also provide food for different bird species. Fraxinus excelsior blossoms in April – May and bears fruits in August – October.

Robinia pseudoacacia is a high tree and honey-bearing plant which belongs to the Leguminosae family. It is also known as White acacia. Robinia pseudoacacia (acacia) reaches a height of 25 metres. It has a branchy crown and shaky grey-brown bark. Its leaves consist of a large number of smaller leaves which are positioned oppositely in the leafy formation. The petiole is short and two small thorns are located in its base. Robinia pseudoacacia reaches a height of 25 metres. It has a branchy crown and shaky grey-brown bark. The natural area of distribution of Robinia pseudoacacia is North America. It grows elsewhere in the world. It withstands low and high temperatures and its best place to thrive on are fertile soils. Robinia pseudoacacia is used as a tree which stabilizes soils. It is planted on many places – parks, alongside roads, private yards and gardens, railways, etc.

Sycamore, Ordinary sycamore (Acer pseudoplatanus, Sycamore maple) is a broad-leaved and deciduous tree belonging to the Aceraceae family. Acer pseudoplatanus is a species of the Acer genus. The genus is sometimes classified in its own family - Aceraceae but is also grouped in Sapindaceae (together with Hippocastanaceae) in the latest version of the system for angiosperms Phyologeny Group (Stevens 2001). It reaches a height of 40 meters and the diameter of its trunk reaches 2.5 metres. It has a thick, broad and massive crown which has the shape of a conversely inverted egg.

Red Oak - Quercus Rubra. American red oak (Quercus rubra) is a deciduous tree of the first magnitude which belongs to the group of red oaks (section Lobatae). Its natural area of distribution covers the Eastern part of the North American continent. This tree has been introduced in Bulgaria since the beginning of 20th century as an ornamental tree due to its remarkable autumn colouration combined with its good tolerability to urban conditions; forest plantations were also formed of red oak which perform forestry, landscape development and rehabilitation functions. The Northern red oak is a photophilous species. Its representatives reach a height up to 20-30 metres (individual species reach up to 49 metres) with an average diameter of the trunk about 50-100 cm (maximum 2.40 metres). Its rate of growth (particularly during the first 10 years) is among the quickest one for the Genus Quercus. The life span of Quercus rubra in optimal conditions is estimated to be over 500 years.

Quercus petraea, also known as Sessile oak and Durmast oak, is a large broad-leaved tree of the Fagaceae family. The species is not protected by the Act on Biological Diversity. The Durmast oak is the national symbol of Ireland. It reaches a height of 30-40 metres. Its crown is ovate-rounded while the crown of older and single trees (in the open air) grows in width. The bark is shallowly cracked and is thinner than that of the ordinary oak. Its distinctive mark (combined with the presence of a petiole) are acorns with their specific shape which are clustered in groups of 2-5 pieces over a strongly shortened axle or sessile. Quercus petraea and Quercus robur are opposites in relation to the presence of a petiole for their leaves and acorns.

Oak (Quercus cerris) is a broad-leaved deciduous tree with well-developed root system which deeply penetrates the ground. Oak is relatively simple to the environmental conditions and it withstands both high and low temperatures. However, when temperatures get extremely low, the cold can cause frost crack to the tree – the water in the tissues freezes and then cracks start forming along the stem. Then pathogenic organisms enter through these cracks. This tree grows on almost all types of soils but it grows best on gray forest soils as well as maroon soils. Oak is a drought-resistant species and grows well in drier and warmer conditions. Oak reaches a height up to 30-35 metres.

Tilia is a tree species with remedial properties in its blossoms. It is classified to the Tiliaceae family. Tilia species are about 40. Some of them are known to us as herbal remedies - Tilia cordata, Tilia platyphyllos, Tilia tomentosa. Tilia reaches 30-40 meters high and its life span is 1000 years. Its crown is very large and greatly branched. The leaves are heart-shaped and are slightly runcinate along the edge of the leaf. They are consecutively positioned on the branches and have long petioles and stipules at their base. Usually the upper surface of the foliage is colored in dark green while the bottom is lighter and is sometimes covered with a flakes. The blossoms are small, delicate and collected in a semi-umbel flowerhead coloured in pale yellow. A single flowerhead reaches 5-7 blossoms while in other Tilia species the blossoms may reach a number of 15. The flowerhead itself has a flowerhead bract which is a long ribbon-shaped leaf. Depending on the Tilia species, this bract may be or not be covered with flakes. The blossoming season starts in early June.