The flower head of the Asteraceae family is its iconic trait, yet little is known about its development. Understanding the fundamentals of the flower head development will help construe the evolution of one of the most successful plant families. In this thesis, we carried out an investigation into the role of auxin in flower head development and patterning in Matricaria inodora and Senecio vulgaris. Auxin is one of the most crucial plant hormones and has been implicated in almost all stages of growth and development. In Matricaria inodora and Senecio vulgaris auxin was found to be involved in flower head development and pattern formation. Manipulation of the endogenous auxin in planta showed homeotic conversions of disc florets to phyllaries or ray florets. Analysis of lateral organ identity genes revealed a concentration dependant response of the identity genes to auxin. The homeotic change of lateral organs in a concentration dependant manner is one of the key traits of a morphogen that had never been documented in planta before. We suggest that auxin acts as a morphogen in the developing flower head to control development and pattern formation. Visualisation of auxin distribution using a Beta-glucuronidase marker gene further confirmed the presence of an auxin gradient in the developing flower head. Auxin appears to have a secondary role in the petal outgrowth and shape in ray florets. In summary, auxin appears to be controlling the development and pattern formation in the flower head through the concentration dependant recruitment of lateral organ identity genes.