Sometimes artists power on in their haste to finish a painting. Details omitted from the master drawing can result in an inaccurate painting. Not having the correct placement of the midrib vein is also something that absolutely stands out in a finished work.
With botanical art there are really no shortcuts. The more information and detail you do in your drawing and colour study, the better the final painting will be.
I write an article for each issue in Back to Basics quarterly magazine and my latest article for the current issue is 'Drawing and Foreshortening Leaves'. A frequent question from students is 'how do I show a foreshortened leaf?" This article takes all the guesswork out of drawing leaves.