I've never thought about it until your question, but:
The building is more important, BUT, the shrubs, grass and trees are essential - you really can't have one without the other, they are part of the building project.
I think you have to also learn to "think like a landscaper." I have three photos that are examples below.
The farmhouse looked strange without a few bushes and weeds growing up around it - there the look required a rather untrimmed, wild look to it. Dino's restaurant and 77 sunset strip, I copied as closely as I could plants and such in photos of the original.
Even something like a diner needs not just some scrubs, but some scrubs arranged in a realistic way, to make it look, well . . . realistic. I actually drove to a shiny aluminum diner near us to take a photo of the plants before I got it right.
![DSCN1413 DSCN1413](https://ogrforum.ogaugerr.com/fileSendAction/fcType/0/fcOid/40004357713671386/filePointer/40004358307370876/fodoid/40004358307370870/imageType/MEDIUM/inlineImage/true/DSCN1413.JPG)
![DSCN1415 DSCN1415](https://ogrforum.ogaugerr.com/fileSendAction/fcType/0/fcOid/40004357713671386/filePointer/40004358307370877/fodoid/40004358307370871/imageType/MEDIUM/inlineImage/true/DSCN1415.JPG)
![DSCN1417 DSCN1417](https://ogrforum.ogaugerr.com/fileSendAction/fcType/0/fcOid/40004357713671386/filePointer/40004358307370878/fodoid/40004358307370872/imageType/MEDIUM/inlineImage/true/DSCN1417.JPG)