They have a similar flavor to onions but are much milder. Spring onions contain vitamins A, C, and K, flavonoids, potassium, calcium, and fiber. The Egyptians, Greeks, Romans, and Chinese all planted and used this vegetable. The spring onion is believed to have originated in the Far East and has been a favorite in China and Japan for centuries COLOUR: Green leaves grading to white at the base, white bulb with some thin green striping. MATURITY: No evidence of flower formation, or brown dry husk on the bulb (over mature). Spring onions are available year-round.