Not really. Actually, there are not research papers or medical textbook shows that looking at greenery will improve eyesight. Greenery does not have any magical sight-improving qualities nor can any color in the spectrum improve your eyesight one bit.
But why so many people think that greenery can improve eyesight, the reason is that greenery is usually at a distance. A grass patch, a group of trees is usually at least a few meters away from us, if not more. This means the eye is focusing at an object far away when we look at greenery. The eye muscles have to change the shape of the natural lens of the eye in order to help it focus for near. The medical term for this muscle action is called accommodation. The more the eye accommodates, i.e. the more near work we do, the more the short-sightedness will increase.
These muscles are relaxed when we look far. This is why we always hear about good eye care habits that include reducing time spent reading, writing and using computers/hand-held devices; and to look far away after every half hour of reading/writing. So, while it is not likely that looking at greenery will help "improve" our vision, it will do us some good for us to look at greenery, or more accurately, looking at objects that are far away as it will help us prevent an increase in short-sightedness.
