These pictures were all taken under the same conditions except aperture--Pentax Kx with 50mm prime lens at various F stops. The buds were near the minimum focus distance--if the subject is farther away the background will not be as blurred at a given aperture.
f1.8. Normal DSLR zoom lenses do not have an aperture this wide/fast. Virtually no background details visible. (click any picture to embiggen)
An example of distance affecting depth of field, this is also same camera and lens at f:3.5--but since it is focused farther away the background is much clearer.
f:7--Buds are almost there, beginning to see the bushes farther back.
f:22, the minimum aperture most cameras have. Buds farther back now show some details.
It is unfortunate that modern cameras don't have a good method of showing depth of field. In the 70's, a manual focus version of the 1.8 50mm used here would have been the standard kit lens. Zoom lenses are quite a bit slower, and therefore dimmer--the kit zooms for my camera are typical, letting in 1/4 to 1/8 the light compared to the 50mm. To counter that the viewfinders have been modified to brighter ones that makes everything appear to be more in focus than it will be on the final picture.