Bulbous vegetables are a type of vegetable that grow from an underground bulb. Leeks, tulips, and tulip bulbs are all examples of bulbous vegetables. Leeks are a four-letter bulbous vegetable with a mild onion flavor. Tulips are a six-letter bulbous vegetable that is often used as a decorative flower. Tulip bulbs are a five-letter bulbous vegetable that can be planted to produce the tulip flower.