Use the word vegetation to refer to all plants and trees collectively, typically those in a specific region. The vegetation in your backyard might look very lush and green in the springtime, unless you forget to water it.
Vegetation, as well as meaning all plant growth, can refer to the growth process of a plant. The lettuce you planted a couple weeks ago is at an early stage of vegetation. Vegetation can also apply to people — or at least to those in a state of inactivity. Think about how slowly plants grow. It’s the same for a person who’s in a state of vegetation. You may sometimes enjoy the mindless vegetation of doing nothing at all.