Early ecologists believed that growth form categories are crucial tools for ecological research. For distinction of plant growth forms, the whole plant appearance is used. There are many classifications of growth forms that may have a few or many categories and either describe diversity of plant growth habits per se, or describe categories that are considered as adaptations to some environmental gradient (e.g. climate or soil) and are called life-forms. The most used classification was developed by Christian Raunkiær and defines life forms that represent plant adaptation to survive a seasonal adversity. The life forms are classified according to position (in respect to the soil surface) of the highest bud that serves for resprouting after seasonal rest. According to Raunkiær’s original idea, the spectrum of the forms in a community should be compared with the theoretical spectrum of the whole world flora. Currently, rather than comparison with a theoretical spectrum, the spectra found in individual communities are compared with one another. The functionality of life form or growth form categories is only rarely experimentally tested.