Pinto bean growth resembles other bean plant maturation, although harvesting can be different. Pintos, which are herbaceous annual Central and South American natives, are considered dry beans, and are often harvested when the seeds are fully mature with a very low moisture content, according to Thomas Jefferson Agricultural Institute. Their skin is mottled and varies in color. The bean meat is a good source of fiber and protein. Pintos are frequently used in southwestern dishes, and they remain an important food crop in the United States.
According to Biology-resources.com, pinto bean and other bean seeds consist of two halves, called cotyledons, which store nutrients. Endosperm cells, which contain moisture and organics like starch, proteins and oils, feed the embryo, or tiny plant, contained between the halves as germination commences. A thick coating protects the seed until it begins to grow. Pinto beans come in many sizes and colors, depending on their variety.
Pinto beans like to grow in fertile, well-drained soil, and grow best and fastest when soil temperature is between 70 and 80 degrees Fahrenheit. For germination to begin, water must enter a small hole, called a micropyle, in the seed coat at the bean's thick inward curvature, causing the seed to swell and split apart, Biology-resources.com states.
The seed's structure continues to change as the plant embryo grows and other seed parts emerge. A radicle, or undeveloped root, pokes out of the seed and begins burrowing into the soil; while a shoot, or plumule, starts pushing upward.
The root continues to develop and form secondary roots, which serve as anchors and draw more water and nutrients from the soil. The shoot pushes through the surface, carrying the cotyledons with it. As the first leaves unfurl, the seed coat is shed.
An intricate, but shallow, root system grows while the plant that's above ground reaches upward. A thicker stem develops, carrying nutrients to the increasing number of leaves that unfurl from it. Via photosynthesis, the leaves turn sunlight into sugar and other organic material necessary for the plant to keep growing.
Blossoms emerge within about 32 to 40 days, and pod development continues for the next 14 days. Pinto bean plants are vine-like, but only reach about 18 inches high, the Thomas Jefferson Agricultural Institute notes.
Complete pod maturation occurs after about 100 days after seed planting, according to the U.S. Department of Agriculture. The pods contain edible seeds that perpetuate the growing process. Harvesting can occur when the pods and seeds are completely dry, or when some pods are brown and the majority are yellow. Seeds should contain 18 percent moisture.