For any species of plant or animal to survive, it must ensure the best possible start in life for its offspring. Some animals nurse their young and move with them to safer ‘crèche’ areas. Others carefully choose where to lay their eggs to ensure plentiful food when their young hatch.
Plants generally do not have the luxury of being able to move to benefit their young. Simply dropping their seeds beneath them is rarely a good strategy, because the adult plant casts shade that would block the seedlings from the sunlight they need to grow.
Most plants therefore rely on an external mechanism to spread their seeds. Some produce seeds that blow in the wind or float on water. A few use spring-loaded mechanisms to catapult their seeds away. Others offer rewards to encourage hungry critters to spread their seeds on their behalf.
Some plants employ a ‘scatter-gun’ approach, producing thousands or even millions of seeds to ensure that at least one or two reach a suitable spot to grow. Others invest lots of energy into making just a few, highly developed seeds (eg coconuts) with mechanisms to give them the best possible chance of germination.
Some plants flower in the summer, set seed then die (annuals). That might fail in a bad summer, but their seeds usually last several years to ensure that some germinate eventually. Others take two years before they are ready to flower and seed (biennials). The majority flower and produce seeds for several, or even many, years (perennials), maximising the chances of spreading their kind.