Seed, a reproductive structure produced by plants as a means of giving rise to new plants similar to the parents. Not all plants produce seedsonly those that bear flowers or cones. And even some of these plants can reproduce by other means, such as by bulbs and runners.

Seeds vary greatly in size, shape, and color. Orchid seeds are scarcely larger than specks of dust, while a coconut seed can weigh as much as 50 pounds (23 kg). The size of a seed does not indicate the size of the plant that will grow from it. For example, a redwood that is 300 feet (90 m) tall grows from a seed that is only 1/6 of an inch (4 mm) long, but a lima bean seed that is one inch (2.5 cm) long produces a plant only two feet (60 cm) tall.

Some seeds are round, some are flat, and some are irregularly shaped. Some have a ridged surface; others are smooth. Seed color varies from species to species, as well as among plants of the same species. Some seeds have a characteristic shading or patterning. It is often possible to identify the species of plant from which the seed comes by the external appearance of the seed.