turns out I was the one wrong! what I did in my assignment is that I'd go around the leaf with my pen and add the details, highlighing all of it in the process and making my drawings visually noisy. here is an example of what I'm talking about http://imgur.com/gallery/JkuKHX9

when I wrote the first comment here I'd initially thought I was adding some kind of gradient to make things look more natural. But even that gradient would look the exact opposite.

the point is: your detailing is correct