The review of general problems connected with modern state of city gardening of St. Petersburg and related to the improvement of the existing assortment of arboreal plants is given. These are the errors in taxa’s identification the usage of synonyms, out of date and mistaken names the emergence of inter-species hybrids. There are unfavourable ecological factors which influence the plants, especially planted along roadsides. There is the necessity to elaborate the new steady and decorative assortment, which is especially important in the age of climate change. This results the wide distribution of Dutch elm disease (since 1998). There is the urgent need to study the ecological peculiarities of plants for landscaping and to sum up the experience of botanic gardens of North-Western Russia and of adjacent Scandinavian countries.