You walk into an area with some withered plants growing next to some healthy ones. The old farmer bends down and examines pulls up a branch with some small leaves on it.
"Now, ye have to get to know yer plants. Each one's like a little child, no two alike. Walk over here -- Yes, come on! Don't be shy, the plants won't bite! -- stand right over the bush. Now bend down an' really look at the plant. Have ye ever studied Herbalism? Excellent! That skill will come in handy right about now.
"Once ye've got yerself acquainted with the bush, ye'll be able to tell at a glance how healthy it is. When ye start pickin' leaves from it, be gentle, an' after each one, look the bush over. If it's still full of blossoms then it's in great shape, an' ye can keep pickin' leaves without hurtin' it too much. Once the blossoms are all gone, it gets a little trickier. But, look at these two. See the difference? This one on the left is still strong, but this one on the right is startin' to look withered. If the bush is strong, you can still pick leaves from it, but be careful, 'cause it might become withered at any time. Once it's started to wither, ye'd best not harvest from it any more, 'cause ye might kill the bush!
Head back.