As soybean plants mature, leaves drop and stems lose their green color. But "green stem syndrome” can prevent the stems from drying down properly and cause the stems to remain green after seeds are mature. Occasionally, green leaves also remain. The green stems are tough, hard to cut, and more likely to plug the combine. It is a natural inclination to wait until the stems lose this green color before harvesting. But harvest should proceed if seed moisture is 13% or lower; as seed quality may suffer, shatter losses will increase, and seed moisture will continue to decrease.