corymb [ KAWR-imb, -im, KOR– ] noun: a racemose inflorescence in which the outer/lower flower stalks are longer than the inner/upper stalks so that they all reach about the same height and in which the outer flowers usually open first; adjective: corymbiform, corymbose
A corymb is a flat-topped or convex inflorescence (flower cluster) shaped by the varying heights of its pedicels (flower stalks). Individual stalks grow upward from different levels on the rachis (main axis), with the outer, lower stalks being longer than the upper, inner stalks so that they all rise to approximately the same height. The pedicels can be arranged in either an alternate or opposite pattern along the rachis.
A simple corymb has unbranched stalks, as exemplified by Vaccinium corymbosum* (northern highbush blueberry). A compound corymb has branched stalks forming smaller secondary corymbs, as found in Aronia (chokeberry), some Crataegus (hawthorn), and Kalmia latifolia* (mountain laurel).
Corymbs are usually an indeterminate or racemose inflorescence where the flowers open from the periphery to the center or from the bottom to the top and continue to grow. However, some plants, like Hydrangea arborescens (wild hydrangea), have determinate or cymose corymbs, where the center or terminal flowers open first, stopping further growth.
Sometimes, corymbs form secondary arrangements. For example, a capitulum is the primary inflorescence of the Asteraceae (the aster or composite family). However, capitula, which are not borne singly, are borne in secondary arrays. When these arrangements are structured like a corymb, they are described as corymbose. If they have the appearance, although not necessarily the structure, of a corymb, they are referred to as corymbiform.
Corymb Inflorescences
(some plants are pictured with fruit to show how the pedicels attach to the rachis)
Corymbiform or Corymbose Inflorescences
*Various published Flora and botanical sites may differ in their descriptions of inflorescences. For example, both Flora of Virginia (FVA) and Flora of North America (FNA) describe Vaccinium inflorescences as racemes. However, FNA further describes the inflorescences of Vaccinium sect. Cyanococcus (and its lower taxa like Vaccinium corymbosum) as corymbs. Likewise, both FVA and FNA describe the inflorescence of Kalmia latifolia as a terminal panicle, while the Manual of the Vascular Flora of the Carolinas says that its inflorescence is a terminal compound corymb.
References
Ashe WW. June 1904. East American Thorns. Journal of the Elisha Mitchell Scientific Society. 20(2): 47-56.
Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico [Online]. 25+ vols. New York and Oxford. http://beta.floranorthamerica.org. (accessed October 23–27, 2025)
Hydrangea arborescens — American hydrangea. Go Botany. © 2025 Native Plant Trust.
Illinois Wildflowers, © 2002-2020 by John Hilty. (http://www.illinoiswildflowers.info/index.htm accessed May 31, 2025).
Kalmia latifolia — mountain American-laurel, mountain laurel. Go Botany. © 2025 Native Plant Trust.
League, KR. 2005. Kalmia latifolia . In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer).
Lobstein M. New York Ironweed (Vernonia Noveboracensis). Prince William Wildflower Society. Virginia Native Plant Society.
Radford AE, Ahles HE, Bell CR. 1964–1983. Manual of the Vascular Flora of the Carolinas. The University of North Carolina Press, page 803.
Vander Kloet SP. Vaccinium sect. Cyanococcus. Volume 8. Flora of North America North of Mexico [Online]. (accessed December 13, 2025)
Weakley AS, Ludwig JC, Townsend JF. 2012. Flora of Virginia. Bland Crowder, ed. Foundation of the Flora of Virginia Project Inc., Richmond. Fort Worth: Botanical Research Institute of Texas Press.