In general flowers are classified on the basis of the presence or absence of different floral parts and the types of flowers are as follows:
A flower is said to be complete, when it has all the four whorls. Examples of these types of flowers are calyx, corolla, androecium and gynoecium e.g., Hibiscus (chinarose), Brassica (mustard) and Datura.
A flower is incomplete, when any one of the four whorl is absent. Examples of these types of flowers are Polyanthes (calyx absent), Beta (corolla absent), Cucurbita male flower (gynoecium absent), female flower (androecium absent).
Bisexual or Hermaphrodite flower
A bisexual flower is that, which contains both the male and female reproductive whorls, i.e., androecium and gynoecium; examples are, Hibiscus (chinarose), Brassica (mustard).
Unisexual or Diclinous flower
A flower is unisexual, when either of the male or the female reproductive organ is absent. Examples of these types of flowers are staminate and pistillate flower of Cucurbita (gourd).
Regular or Actinomorphic flower
A flower is said to be regular types of flowers, when all the floral members of the respective whorls (viz., sepals, petals, stamens, carpels) are having equal size and shape and are more or less equidistant from each other, hence the flower can be dissected into two equal halves at any plane, e.g., Hibiscus (chinarose); Datura.
Irregular or Zygomorphic flower
A flower is said to be irregular, when the floral members vary in their size and shape, and hence the flower can be cut into two equal halves through one plane only ; example Pisum sativum, (pea). Sometimes the flowers cannot even be cut into two equal halves even through one plane and they are called asymmetrically zygomorphic, example Canna (B. Kalabati).
Types of flowers are said to be cyclic, when all the four whorls (viz., sepals, petals, stamens and pistils) are arranged in whorled or verticellate manner example, Hibiscus (chinarose).
Types of flowers are said to be acyclic, when the floral members are arranged spirally on the thalamus. e.g., Paoenia.
The floral members of a spirocyclic flower are both arranged spiral as well as in whorled manner example, Nymphaea, Magnolia.
The types of flowers are said to be naked, because neither calyx nor corolla is present, example Male flower within the cyathium of Pedilanthus.
A flower is said to be neuter, when it is devoid of both male androecium and female gynoecium, as an example the Ray florets of sunflower.
The types of flowers are said to be monochlamydous, when either calyx or corolla is present, e.g., Polyanthes (tuberose).
A normal flower with both the accessory whorls, i.e., calyx and corolla is called dichlamydous. Example, Hibiscus (chinarose).
The types of flowers are in which the floral members are in multiples of whole numbers. They may be of the following types:
i) Trimerous : The number of floral whorls are three or in multiples of three, e.g., Polyanthes (tuberose).
ii) Tetramerous : The floral whorls are four or in multiples of four e.g., Brassica (mustard).
iii) Pentamerous : The floral whorls are five or in multiples of five, e.g., Most common in dicot flowers like in Hibiscus (chinarose).