An investigation into the performance of species in ecologically based ornamental herbaceous vegetation, with particular reference to competition in productive environments.

The use of ornamental herbaceous plants in ecologically based planting schemes (EBPS) requires selection of species which are compatible, particularly for productive environments where competition is likely to be intense. Competitor, Stress tolerator, Ruderal (CSR) theory is considered and rejected as a guide to plant selection, although some of its insights are regarded as valuable. Competition between component taxa in EBPS is considered a key issue. Researching competition for practitioners in horticulture and allied industries involves a less reductionist and a greater observational methodology than is customary amongst plant ecologists. Simple competition trials are evaluated with regard to not just their outcomes in terms of understanding competition, but also their suitability for practitioners. A system for the classification of ornamental herbaceous plants is suggested, based on easily recognised aspects of their morphology and phenology. Plant architecture, the potential to spread through ramets and an ability to exploit growing seasons of various lengths are regarded as key variables. Relationships between the suggested categories and estimates of competitive performance in garden and EBPS conditions are considered. Biomass, as represented by a combination of canopy height and spread, an ability to spread extensively through ramets and an ability to grow over a long growing season are suggested as key factors in predicting both long-term survival and competitive performance. A knowledge of plant traits is suggested as being of key importance to practitioners in predicting plant performance over time, more so than comparison of environmental conditions in the region of origin and in cultivation. The contribution of genetically derived traits to distinct growth characteristics in different growing conditions is recognised, and their relevance to practitioners working with a variety of different design methodologies is discussed.