Sunflower is one of the few crop species that originated in North America. Records indicate that the western Native Americans domesticated the crop as early as 1000 BC. Its strong taproot and phototropic broadleaves allows the plant to increase light interception, photosynthesis, and resource use from soil. Although typically harvested for its seed, sunflower can also be used as a silage crop when seed crop is not possible due to early frost or other reasons. Earlier research has indicated that sunflower yields are generally less than corn but the nutritional quality is often higher.