Mustard greens and spring greens are two different varieties of vegetables. Mustard is a cruciferous plant with pinnately lobed leaves that have a pungent flavor and are often used in cooking to add flavor. Spring greens, on the other hand, are a heart vegetable with round or ovate leaves that are tender and crunchy, making them suitable for raw or stir-fried dishes. Mustard is mainly used to make mustard sauce, mustard and other condiments, but also can be used in stir-fry or cold; spring vegetables are commonly used in cold, hot pot, stir-fry and other cooking methods.