The life cycle of all flowering plants depends whether they are annuals, perennials or biennials, these words describing how long the plant lives. Annuals live for one growing season, so gardener must replant them annually. Biennials live for two growing seasons and perennials live for at least three growing seasons. Perennials include trees, some of which can live for many hundreds of years.
Though flowering plants can reproduce through vegetative propagation--stem cuttings, division and so on--vegetative propagation is more of nature's back-up plan. Flowering plants' main reproductive method is through seeds.
Plants disperse seeds by dropping or even propelling them, by relying on the wind to blow them to ground or by relying on animals to either eat the seeds or snag seeds on their coats as they brush by the plant. When a seed finds favorable conditions, it awakens, and an embryonic plant within grows, feeding on endosperm tissue contained in the seed.
The embryonic plant emerges from the seed sporting either one or two leaf-like structures called cotyledons. Those with one cotyledon are monocotyledons--monocots--those with two are dicots--dicotyledons. While the cotyledons emerge into the light, roots dig down into the dark underground.
As the plant matures, it grows true leaves and other vegetative parts like stems and branches. How fast and how long a plant adds vegetative parts depends a lot on whether the plant is an annual, biennial or perennial.
Flowers emerge when the plant is ready to reproduce. In annuals, this happens during the plant's first growing season, in biennials, it happens during the second season, while perennials tend to take their time, sometimes waiting many years before finally flowering. Some flowers produce sperm-containing pollen--male flowers--others contain eggs--females--some have both, being bisexual.
The pollen must get to the female parts of flowers so the flower can be fertilized. Small flowers rely on the wind for this. Showy flowers court birds, bugs and animals, drawing them near with nectar, scent, color and markings. The creatures pick up pollen when they visit, transferring pollen when they move on to another flower.
Fruiting and Seed
Once a flower has been pollinated, double fertilization takes place. Double fertilization is unique to flowering plants, which are collectively known as angiosperms. In double fertilization, one sperm fertilizes the egg, while another fuses with what are called polar nuclei, becoming the endosperm tissue within a seed that provides food for an embryonic plant. Meanwhile, floral parts or the flower's ovary swell and ripen around the seed, becoming fruit.
In pods, the ovary wall is the pod itself. In fruits like apples, the fleshy part is the transformed floral tube of the flower and the core is the transformed ovary. Annuals and biennials die after seeds have been created. Perennials can flower many times before dying.
Biennials and perennials also have a dormant stage. Instead of flowering during their first growing season, biennials produce food storage organs--tubers, bulbs and corms--these fueling new growth during a second and final growing season.
After creating the organs, biennials go dormant until awakening the next spring to complete their life cycle. Perennials also enter dormancy. In deciduous perennials, the dormant stage is marked by leaf loss, with new leaves bursting forth the following spring, perhaps including flowers.