To capture the essence and physicality of a plant, or a bird , or a feather you have to give up thinking about the design and what you think you know exists. There is no "It should go there" in nature. You have to trust your observational skill and let your eyes relax onto the object of contemplation. The hand must be ready , a willing tool. Your own will coming through your hand must be prepared to fade into the background betraying your presence in the drawing with only a tremor or flick of line, your subconscious signature. The role your own personality plays in the observation of nature is in the germination of interest in something hidden or overlooked. Once the eyes and hands are engaged it is your task to just observe, look closely. Open your brain so it is free from assumption to see what is in front of your eyes.
Would DA appreciate the addition of and extra vein on a leaf for "balance"? No he would not. Anthropomorphizing subjects leads to mistaken conclusions in both art and science.