Taraxacum is a rather intricate genus, in which about 2000 microspecies have been described. In our laboratory, the biosystematics and ecology of this genus are under investigation. In the Netherlands, Taraxacum exhibits abundant flowering in early spring. To test the hypothesis that this flowering is influenced by the amount of biomass present in the tap-root in the previous autumn, an experiment was carried out with the microspecies T. ekmanii Dt, T. hollandicum v.S. and T. hygrophilum v.S. 40 Tap-roots of each species were weighed and planted in a Lolium perenne L. lawn in November, 1978. The plants were dug up in May, 1979, and dried. The relations between the fresh weights of the tap-roots in November and some characteristics of the corresponding plants in May were analysed with linear regression and rank-correlation methods.