Germination Stages for Lima Bean Seeds

Moisture Absorption and Swelling

• Lima beans, like other seeds, require warm temperatures and moisture to begin the germination process. Presoaking the seed in water can help to speed up germination. First the seed coating that contains the embryo and the endosperm that provides food for the emerging plant begin to absorb water from the surrounding medium. The moisture often dilutes the chemicals that keep the seed in a state of dormancy. The moisture then activates growth enzymes that begin cell division within the seed. These cells develop according to individual DNA patterns to do particular tasks within the plant.

Root Development

• The seed swells with moisture, triggering the development of a root, called the radicle, from the bottom of the seed. This root holds the plant in place in the soil and allows the developing seed to absorb water and nutrients from the surrounding soil, according to Washington State University extension agent Holly S. Kennell. The roots continue to extend, allowing increasing support for the growing stem and leaf cells.

Cotyledon Emergence

• Cell growth causes the hypocotyl arch of the stem to emerge from the top of the seed and then, from the surface of the soil. Gradually, this stem straightens out to hold the cotyledons or seed coverings. These are the first leaves seen above ground.

  Emergence of the leaves occurs in four to eight days, according to Texas A&M University horticulturalist Roland Roberts. These cotyledons are generally larger and stronger than the true leaves of the bean plant and their function is to break the soil above the seed, making it easier for the true leaves to emerge.

True Leaf Development

• The cotyledons fall away, exposing the first true leaves of the lima bean plant. These are quite fragile at first and should be monitored closely for adequate moisture until the stems and leaves grow stronger. Inadequate irrigation at this point will cause the newly emerged plant to shrivel and die. Conversely, adding too much water to the growing seedling may cause root rot and collapse of the seedling. The lima bean plant then extends and adds leaves in preparation for eventual flowering, fruiting and seed production.