Cultivar classification in Tulipa L. (Liliaceae)

A total of 43 Tulipa gesneriana (section Tulipa) cultivars, 25 cultivars and wild accessions belonging to 11 species of sections Tulipa and Eichleres and three species hybrids were subjected to multivariate analysis based on data of 30 morphological characters recorded in two subsequent years. The main division according to earliness of flowering, which has been in use since Clusius made this division early in the 17th century, was confirmed by the distribution of the accessions in the principal component plots. The repeatability of measurements is high for most characters, as is deduced from the Pearson correlation coefficient per character between years. A cultivar classification system is proposed with two levels. The acceptance of a two-level cultivar classification is based on the structure of variation encountered and is a continuation of four centuries of tulip cultivar classification. The top level should include three supergroups for Early, Mid-season and Late flowering cultivars. Recommendations are made concerning the restoration of certain cultivar-groups and the placement of some cultivars. It can be concluded that multivariate methods provide basic insight in the diversity among cultivars. This information can be used as a basis for the construction of cultivar classifications.