Say you've been offline for awhile, unable to check your plants. Or you have forgotten to do so. A warning would be nice, like the tutorial tips from various professors and NPCs in the Spiral. Say if your plants have had needs for awhile and are about to start wilting, Marley, Barley, Charley or whoever could give you a tutorial tips reminding you to check on them before they start wilting and/or dying.
Plants only wilt when you leave them with needs. And they only die if you see them wilting and ignore them again.
Take care of all needs before you leave the area, and your plants will be fine even if you log off and stay away for a year.
If there's going to be a warning that would be useful, it would have to be a ping that reminds you to take care of needs BEFORE you port away or log out of your garden. Something like, "Are you sure you want to leave? Your plants still need water/have pests/etc. If you don't take care of them now, your plants will be wilted when you return..."
Or, you could just look at the little round gardening icon at the right side of your screen. It shows green when your plants are fine, yellow when there are needs, and red when there's wilting or death. Don't leave until that little icon shows green, happy plants.
Alia Misthaven