Abstract
One of the tasks of a program of greenery monitoring is the task of determination of plant species which are the most adapted for severe ecological conditions of urban environment with the purpose of planning of various measures to be performed at amenity planting objects. Taking into account that even a highly qualified expert may not always be absolutely sure of assigning plants to one of the categories of state we formalize the results of expert evaluation of plants with the help of semantic spaces. These formalizations are used for clustering of plant species and for determination their ratings.