Traditionally, plants were classified based on their morphology, which involves the observable physical characteristics like shape, structure, color, and size. While this method is straightforward, it can often lead to misidentifications and inconsistencies. Morphology can be influenced by environmental factors, leading to significant variation within a single species. This makes it difficult to accurately categorize plants solely on their appearance.

For example, plants within the same genus can exhibit vastly different morphologies. Take the genus Senecio from the Asteraceae family. Some species of Senecio look remarkably similar to daisies, with their iconic yellow or white ray flowers. Others, however, are succulent and bear a striking resemblance to cacti, with thick, fleshy leaves adapted to arid environments. Despite their different appearances, these species are genetically related and belong to the same genus. This highlights the limitations of morphology-based classification.