Inflorescence: Flower Arrangement on a Stem

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An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. It is categorized on the basis of the arrangement of flowers on a main axis (peduncle) and by the timing of its flowering (determinate and indeterminate).

Types of Inflorescence

  • Catkin – A spike with only pistillate or staminate flowers (alder, poplar, walnut, and willows)
  • Composite or Head – A daisy-type flower composed of ray flowers (usually sterile with attractive, colored petals) around the edge and disc flowers that develop into seed in center of the flat head (sunflower and aster) On some composites, the ray and disc flowers are similar (chrysanthemums and dahlias)
  • Corymb – Stemlets (pedicels) arranged along main stem. Outer florets have longer pedicals than inner florets giving the display a flat top. (yarrow, crabapple)
  • Cyme – A determinate, flat or convex flower, with inner floret opening first.
Types of Inflorescence

Types of Inflorescence

  • Panicle – An indeterminate flower with repeated branching. It can be made up of racemes, spikes, corymbs, or umbels. (begonia)
  • Raceme – A modification of a spike with flowers attached to a main stem (peduncle) by stemlets (pedicel). (snapdragon, bleeding heart, Canterbury bells)
  • Solitary (or single) – One flower per stem (tulip, crocus)
  • Spadix – Showy part is a bract or spathe, partially surrounding the male and female flowers inside. (calla, caladium)
  • Spike – Flowers attached to main stem, without stemlets, bottom florets open first. (gladiolus, ajuga and gayfeather)
  • Umbel – Florets with stemlets attached to main stem at one central point, forming a flat or rounded top. Outer florets open first. (dill, onion)
  • Symmetrical – Symmetrical flowers (lily)
  • Asymmetrical – Asymmetrical flowers (snapdragon)

Source: ext.colostate.edu

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