They are sentient. All plants are, from flowers to grass. They require food and water to grow just like us, and they reproduce. They respond to sunlight and music. From what I read, that fresh lawn smell is a chemical grass let off when they are in danger to alert the grass around them. They are literally crying out in pain everytime the lawn gets cut.
If u wanna be vegan or vegetarian that's your choice, but don't sit on a pedestal like u r better than anyone, you eat dead life forms just like meat eaters, there is no difference.
And if u vegan, stay true to your cause. Stop murdering the plants. Stop mowing your lawn. Let the grass grow