All plants and trees, whether flowering or not, go through four basic stages of life: germination, growth, reproduction and death. As explained by the U.S. Fish and Wildlife Service, "plants are categorized by three life history strategies: annual (one year), biennial (two years), and perennial (many years)." Simply put, a seed germinates, and becomes a seedling. The seeding grows into a plant with roots, stems and leaves. The plant forms a flower when mature. The flower (or cone) forms a seed.
The Oregon State University "Glossary of Botany Terminology" defines germination as: "The initial growth phase of a seed, spore or pollen grain." Seeds generally have three main parts: The seed coat (outer layer) protects the embryo (new plant) and endosperm (stored food). Plants have either one or two cotyledons. These structures resembling tiny leaves process the stored food until the plant forms its first roots and leaves.
Once the roots and stems have formed, the plant enters a period of growth. Stems and roots continue to enlarge, and leaves are formed. During this time, the plant creates and processes its own food through photosynthesis. Leaves and roots take vital nutrients from the air, sun and soil. Stems or shoots transfer this food via vascular tissues throughout the plant. This process continues until the plant reaches reproductive maturity.
Once mature, the plant forms its reproductive parts. In the case of biennial plants, this occurs after a period of winter dormancy. Perfect flowers contain both male and female reproductive parts, while imperfect flowers lack one or the other. By some environmental means (wind, insects, rain) pollen from the stamen (male part) is transferred to the pistil (female part). Fertilization occurs, and the seeds of flowering plants form in a ripened ovary, or fruit. In the case of coniferous plants and trees, the seeds are formed inside cones and are protected by a strong outer layer. Some plants also recreate themselves through vegetative reproduction. Examples of vegetative reproductive structures listed by the U.S. Fish and Wildlife Service "are rhizomes (underground stems) and stolons (stems running along the surface of the ground) from which new plants develop."
Death or Dormancy
Once the seeds have formed, the plant enters its final life stage. For annuals, or biennials in their second year, this is death. The stems, leaves and roots die back. The fruits fall to the ground, and the new seeds are in a position to germinate once again. For perennials, this stage is dormancy. Herbaceous perennials lose their above-ground structures for protection, while woody plants may lose leaves. Above-ground growth ceases for a time, and it may be many years before death finally occurs.