Before the arrival of colonialism in 1881, Tunisia was based mainly on the agriculture. Despite the early settlement of the nomadic population, major urban centers, with the exception of the capital, Tunis, were almost rare. Tunisian towns that were built by the style of Moroccan Arabic cities were simultaneously known as the religious, political, economical (and especially commercial) center of the country and they were under the command of the Bey. The city could be opened to the main directions and join the widespread cultivation of citrus and olive plantations. At the time, Agriculture and Business were the foundation of life for the city. In this case, the Tunisian residents had practical and economical experiences from the trees. In this paper, the transformation of the concept of public space since the pre-colonial period (late 19th century) to the present time in Tunisia is followed with a focus on significant times of history. Therefore, it tries to discuss the relationship of trees and the city in these special times; from the time when it was a part of private space ( the time where there were no public spaces), to the time when it carried a new function in common spaces and displayed a new relationship between the citizens and public spaces in the colonial period. The colonialism changed the public opinion about public spaces. Before tree colonialism; this natural element was absent in the tradi-tional culture of public spaces and the commercial and religious activi-ties were predominant in these spaces. There was a different relationship between a person and a tree in the private space of a traditional Tunisian house. This semi-hidden and simple relationship which was also known as a public (common) imagination of citizens was pretty worthy. The pub-lic space only had meaning in religious buildings such as mosques and schools. No tree was seen in public spaces because these spaces were allocated to religious and commercial (market) activities. Trees were lo-cated in houses especially in patios to offer a relaxing space. In this case, not only the functional aspect (beauty, freshness, fragrance, fruit) were considered, but also they reminded a paradise in Islamic tradition. Increasing of trees in Europeanized city began during French colonial-ism by relying on the concept of public space and its role in the struc-ture of urban spaces. That resulted in organized cities with linear roads, streets and squares full of planted trees and open spaces, which were appropriate for impeding diseases such as cholera and plague, unaware of traditional central cities. The new decorative function of trees in new urban spaces and their network structures (streets) was the new policy of colonialism for companying the traditional culture of public spaces in Tunis with the concept of public space required for rapid communication, readability and interaction. Since the officials believed that the modern form of the city did not con-flict their demands, there were a little change in the urban structure of colonial period after the independence of Tunisia. As a result, no basic changes were made in spatial organization neither of the city nor in the exterior spaces of Europeanized city. The migration of the rural population to urban spaces was noticeable since 1970. Consequently, the officials began to build new urban spaces and two main interventions were con-ducted in the North and West sides of the city. Tunis City has been constantly developing mostly in northern and south northern regions since 1980. New neighborhoods almost had the qualities of the adjacent neighborhoods as the northern developments included rich neighbors and west developments were allocated to poor ones. The northern part of the city continued developing in form of villas, buildings and other forms of housing. Therefore, after Tunisia's independence, the «Europeanized» city de-velopment was mainly focused on the concepts of public space which were planned in future urban organization in colonial period. The conse-quent was a duality in the concept of space; a treeless traditional city and a functional, beautiful and useful public space with plenty of trees which reminds the colonial period. [ABSTRACT FROM AUTHOR]