Northern Ontario Plant Database

Inflorescence Types

• Spike - an elongate, unbranched, indeterminate inflorescence with sessile flowers.
• Spikelet - a small spike, characteristic of grasses and sedges.
• Raceme - an elongate, unbranched, indeterminate inflorescence with pedicelled flowers.
• Panicle - a branched raceme.
• Corymb - a flat-topped raceme with elongate pedicels reaching the same level.
• Compound Corymb - a branched corymb.
• Umbel - a flat-topped or rounded inflorescence with the pedicels originating from a common point. Umbels can be determinate or indeterminate.
• Compound Umbel - a branched umbel, with primary rays arising from a common point, and    secondary umbels arising from the tip of the primary rays.
• Capitulum (or head) - a dense vertically compressed inflorescence with sessile flowers on a receptacle and subtended by an involucre of phyllaries, characteristic of the Asteraceae. Heads can be determinate or indeterminate.
• Thyrse - a many-flowered inflorescence with an indeterminate central axis and many opposite, lateral dichasia; a mixed inflorescence, with determinate and indeterminate shoots.

• Simple Cyme or Dichasium - a determinate inflorescence with 2 dichotomous lateral branches and pedicles of equal length.
• Compound Dichasium - a branched dichasium
• Compound Cyme - a determinate thyrse.
• Helicoid Cyme(or bostryx) - a determinate cyme in which the branches develop only on 1 side, due to the abortion of opposing paired bud, the inflorescence thus appearing simple.
• Cincinnus - a tight, modified helicoid cyme in which the pedicels are very short.
• Scorpioid Cyme(or rhipidium) - a zig-zag determinate cyme with branches developing alternately    on opposite sides of the rachis, due to abortion of opposing paired bud.