Flowering plants are widely classified into three groups--annuals, perennials and biennials. Marigolds and tomatoes are annuals that die after one life cycle. Flowers such as roses, daisies, daffodils and tulips are perennials that wither in the winter and frost, but bloom again next spring. Biennials such as foxglove and carrots, bloom the second year of their growth, but self-seed and die.
Most garden flowers contain male and female reproductive organs. Stamen, the male reproductive organ, exists in the center of each flower. Each stamen comprises a long filament with an oblong parcel on one end, known as the antlers. Antlers are usually yellow or orange because they contain pollen. The female reproductive parts are called carpels, which comprise a stem (called style) and a slightly swollen end (called stigma) arising from the ovary.
Pollination and Fertilization
Pollination occurs when wind, birds, butterflies, bees, insects or hummingbirds carry pollen from the antlers to the stigma when searching for nectar. A flower self-pollinates when male and female parts ripen together. The grains of pollen release tubes that penetrate the stigma, then the style and finally the ovary, where each pierces the nucleus of a single egg. Some flowers produce one seed, while others have many in a single flower. This process of fertilization is similar to the human reproduction.
After fertilization, the eggs develop into the seed, while the ovary wall becomes the fruit that contains them. This tough, protective coating contains nourishment for the growing plant. A layer called the endosperm stores short-term nutrients and protects the seed, while two cotyledons store long-term nutrition.
Seeds are dispersed by a number of methods. Some flowering plants self-disperse, shooting seeds in all directions when they burst due to excessive heat. Animals eat fruit or flowers and excrete them, thus helping in dispersal. Wind and rainfall also assist seed dispersal. DIspersal of seeds is essential to separate and thus eliminate competition between the seeds and parent plant, and to ensure seeds reach new areas so they grow into new plants.
Sunlight, water, nutrients in the hard casing and correct temperature are essential elements that assist the dispersed seed in germination. Under favorable conditions, the hard casing or shell cracks open, the seed sprouts and sends out roots in the ground. This process is called germination. Depending on the species, germination may take a few days to several weeks. Soon a few leaves (called cotyledons) appear on the shoot. These leaves assist the plant in photosynthesis, so the young plant produces its own food and grows bigger. The roots grow and spread in the soil as the plant matures and the number of leaves increase. Eventually, tiny buds appear to protect developing flowers. Buds develop into blooms, complete with petals and male and female reproductive organs. The stamen produces pollen, and a new cycle starts.