Brassica rapa is a plant species growing in various widely cultivated forms including the turnip; napa cabbage, bomdong, bok choy, and rapini. The oil made from the seed is sometimes also called canola or colza.
Field mustard is an upright winter annual or biennial that is a member of the mustard family (Brassicaceae). Plants exist as basal rosettes until flowering stems develop at maturity, usually in the second year. Plants grow 1 to 3 (or 4) ft tall from a sometimes fleshy, enlarged taproot, with a many-branched stem. The foliage is generally hairless and sometimes covered with a whitish film. Lower leaves can reach 12 inches long, have a large central lobe, and usually one to four pairs of smaller side lobes. Upper leaves are smaller, non-lobed, and have a pointed tip and widened, clasping base. The bright yellow flowers are clustered at stem tops and have four petals that are ¼ to ½ inch long. Plants flower from January to September. It can be invasive in western parts of the US and Canada.