In cities, the increase of artificial surfaces to the detriment of natural areas deteriorates the environmental quality and energy consumption. The VegDUD project is an interdisciplinary assessment of vegetal technics projected in the future dense city with a focus on climatology, hydrology, energy and ambiences. It aims at increasing the necessary knowledge to orientate urban planners and policy makers. The problem is tackled from several complementary points of view: - Practises: What are the traditional and new practises of urban vegetation? After some initial surveys we focus our researches on five families of vegetal devices. - Tools: Can we quantify vegetation environmental impacts? What are the best spatial and temporal scales to assess them? How do they combine with urban morphology? Urban vegetation representations are implemented in models of climatology, hydrology, sound propagation and building energy from the architectural scale up to the city scale. Measurement techniques and experimental campaigns are developed to understand the physical processes generated by new vegetation devices and to validate our models. - Documentation: Can we rapidly acquire a sufficient knowledge of urban vegetation presence at a large scale? We develop a communal geographical information system (GIS) to integrate the results of field surveys, propose urban development simulations and render the building-vegetation interactions in the actual and future cities. - Analysis: What will be the long-term impacts of the present policies? What are the possible alternatives? We compare retrospective and prospective simulations using our models. With these physical assessments, economical constraints, sensible aspects and vegetation practises are also considered.