The period of time during which flowers are open (the calyptra has fallen) is called bloom (also flowering or anthesis) and can last from 1 to 3 weeks depending on weather conditions. Photo by Patty Skinkis, Oregon State University. The majority of commercial grapevine varieties have perfect flowers, that is, both male and female components.Īn individual grape flower is shown with floral parts labeled. Vines with female, pistillate flowers need nearby vines with staminate or perfect flowers to produce fruit. Pepin) have either pistillate (female) or staminate male flowers - that is, the entire vine is either male or female. Wild grapevines, rootstocks (and a few cultivated varieties such as St. The anthers produce many yellow pollen grains, which contain sperm. The broad base of the pistil is the ovary, and it consists of two internal compartments, each having two ovules containing an embryo sac with a single egg.
The pistil is roughly conical in shape, with the base disproportionately larger than the top, and the tip (called the stigma) slightly flared.
A flower consists of a single pistil (female organ) and five stamens, each tipped with an anther (male organ). The cap encloses the reproductive organs and other tissues within the flower. The grape flower does not have conspicuous petals, instead, the petals are fused into a green structure termed the calyptra, but commonly referred to as the cap. Illustrations courtesy of Eric Stafne, Mississippi State University. Grape flowers from initial formation to cap fall to pre-fertilization (left to right).