Although a large number of studies describe sustainability in horticulture for individual crops or use individual sustainability characteristics as examples, there is still a lack of information on what consumers regard as being the relevant criteria for sustainability in horticultural production in the German market. The aim of this paper is to provide a broad overview of the relevance of different sustainability characteristics for flowers and ornamental plants as well as for fruit and vegetables from a consumer perspective. First, the sustainability characteristics from the literature were grouped according to the four sustainability dimensions of ecology, economy, and social and corporate responsibility. Second, an exploratory online consumer survey was conducted for both non-food horticulture (ornamental plants and nursery products) and food horticulture (open field fruit and vegetables) with the aim of determining the initial significant indicators for various sustainability characteristics for consumers. A confirmatory factor analysis confirmed the four dimensions of the literature research. According to the survey results, the characteristics of ecology were highly relevant to the respondents, followed by the characteristics of social sustainability. However, some characteristics of social sustainability and corporate responsibility could not be confirmed by the model.