The branch of biology that deals with plant studies is called botany. According to this discipline, flowers are specialized structures responsible for fertilization purposes. Every blossoming plant, including common grass, have these structures, which differ in color, shape, size, etc., amongst other features. Also, the mode of their arrangement in the stalk is studied under types of inflorescence.
The whorls represents the four basic parts of a flower, which are arranged on the receptacle. The male and female reproductive structures (androecium and gynoecium respectively) are essential whorls, while the sepals (calyx) and petals (corolla) are accessory parts to mediate fertilization.
Classification of Flowers
Based on Sexuality
According to the presence and absence of the essential whorls, there are two kinds of flowers:
Bisexual: Also referred to as perfect flower, it bears both the reproductive structures in the same bloom. Examples are hibiscus, rose, lily, etc. When they have sepals and petals, they are called complete flowers.
Unisexual: Also known as imperfect flower, it possesses only one functional reproductive structure, either androecium or gynoecium. Accordingly, it is known as male or female flower. Examples are cucumber, pumpkin, papaya, etc.
Based on Morphology
Morphology varies from one type of plant to another, basically in terms of calyx and corolla.
Polypetalous/Polysepalous: In this type, the petals are free and separated each other. Familiar examples are camellia and rose. Likewise, the one with free sepals is called polysepalous flower. Examples are rose and magnolia.
Gamopetalous/Gamosepalous: Also known as sympetalous flower, their petals are fused together, either partly or completely. Examples include elderberry and blueberry. Similarly, a bloom bearing partially or fully fused sepals, is called gamosepalous flower. Examples are periwinkle and hibiscus.
Based on Symmetry
A flower can be divided in one or many planes, to give two or more similar parts. This attribute is called floral symmetry and based on it, there are two kinds of blooms.
Actinomorphic: It bears similar petals and can be separated into many equal halves, which are mirror images of each other. They are radially symmetrical, and examples include hibiscus, buttercup, clematis, etc.
Zygomorphic: It can be divided in only one plane, so as to give two equal halves. The shape and size of petals and sepals are different in this bloom type. They are bilaterally symmetrical and examples include orchids, digitalis, lavender, snapdragon, etc.
Based on Position
Development of flowers in a stalk may vary from one plant to another. Depending on whether they are borne in the terminal position or not, they are of two kinds:
Axillary: In case of this type, a single one or a group of blooms are developed in the same manner as an axillary bud. They are borne in the junction between the leaf petiole and the stem. The hibiscus and periwinkle plants produce such types of blossoms.
Terminal: In this type, a single one or a group of blooms are borne in the terminal end of a branch. The terminal bud matures into a flower (or flower bunch) and dies out. Examples are nerium and magnolia.
Based on Inflorescence
Inflorescence is defined as the basic pattern for arrangement of blooms in the flowering stalk. With respect to inflorescence, they are of two types:
Racemose: These blossoms are developed in an indeterminate branch, which grows continuously. The youngest blooms are present at the tip, while the base represents oldest ones. Examples are caesalpinia, mulberry, and coriander.
Cymose: It is exactly opposite to the previous type, where the axis or branch has a determinate growth. The oldest blossoms are present in the tip portion, while successively younger ones are developed below them. Examples are jasmine, hibiscus, and nerium.
Based on Blooming Season
Annual: These blooms thrive and produce seeds in the sowing season itself. Or in other words, it lasts for only one season, and you will need to replant them again in the coming season. Examples are marigold, petunia, impatiens, and zinnia.
Biennial: These blossoms thrive in the second year of plantation, as the plant develops vegetative parts in the first growing season. Examples include Sweet William, foxglove, and dicentra.
Perennial: They require least maintenance for the gardener, and they bloom recurrently, as the flowering period arrives. You do not have to uproot these plants in every season. Examples are rose, dahlia, common chicory, and begonia.
Though flowers can be classified in myriad ways, the above classification gives a brief idea about their different types.