In gardening and botanical
terminology, a volunteer
is a plant that grows on its own, rather than being deliberately planted by a human farmer or gardener. Volunteers often grow from seeds that float in on the wind, are dropped by birds, or are inadvertently mixed into compost
before it is used.
Unlike weeds, which are unwanted plants, a volunteer may be encouraged once it appears, being watered, fertilized, or otherwise cared for.