The name pinto bean comes from the Spanish word for painted: pinto. The bean is characterized by a mottled skin, and is the most common bean in the United States, and is staple of southern and southwestern cooking. When cooked, the bean takes on a uniform brown color.
The bean itself is a seed. Bean seeds are found in the pods of bean plants. The structure of bean seeds is common to all bean plants in that it has a seed shell and an embryo of a bean plant as well as the initial carbohydrates and nutrients that a bean sprout needs to begin the chemical process for germination and to grow and develop into a mature bean plant. The nutrients are known as cotyledons, and in pinto beans they are split into two halves. This causes scientists to classify pinto beans as dicots or dicotyledon. The embryonic plant nestles on one end of the bean between the two halves of the cotyledons.
Germination can happen quickly after a bean is planted. The typical time for a bean to sprout is within 8 days. During this time, the seed coating loosens, and the cotyledon begins the chemical reaction that leads to the plant embryo growing. The embryo's primary root emerges and grows downward while a stem with the first two leaves on it will grow up through the soil and into the sunlight.
Tiny root hairs will grow from the primary root, and the seedling will begin to take in water and nutrients from the soil. Once the plant emerges from the soil, it begins to straighten. Although some beans form on bushes, the structure of the pinto bean is a climbing vine. In gardens and commercial crop growth, the vine will grow straight up if the farmer or grower trains it up a trellis.
As the plant matures, it will begin the process of producing new beans through sexual reproduction. A pinto bean plant produces tiny flowers after the first 30 days of growth. These flowers will cross pollinate with other pinto bean flowers. Once the plant is pollinated, the flower dies, and a seed pod begins to form on the stem. The typical pod may contain between four and seven beans. It may take up to 90 days for a bean plant to grow from a seed to the harvesting stage.