A plant that completes its life cycle in one year is called an annual.
An annual plant germinates, grows, flowers, produces seeds, and dies within a single growing season. The phrase “one year” is a useful shortcut, but botanists often define the cycle by one season rather than exactly 12 months. In some climates, an annual may complete its entire life cycle in only a few weeks.
Annuals survive from one generation to the next mainly through seeds. This strategy allows plants to take advantage of temporary conditions such as disturbed soil, seasonal rainfall, or a brief period of warmth. Common annuals include peas, beans, marigolds, sunflowers, and many weeds. Some annuals are planted deliberately because they flower or produce food quickly.
The main mix-up is with perennials and biennials. Perennials live for more than two years, often flowering repeatedly, while biennials generally spend their first year growing leaves and roots, then flower and set seed in their second year before dying. “Ephemeral” describes a short-lived plant or plant part, but it is not the standard category for a one-season life cycle.