How much space to give plants/shrubs?

ClubDead

The shady area in my garden (L shape that covers about 12 feet x 8 feet) has a conifer some cabbage trees and a rose bush. However the ground is just soil. I think different types of ferns would look good but how much space do I need to give the rose bush and conifer? Will I damage their roots buy planting near to them? Is there a general rule (give each plant/tree x amount of space)? Thank you.

Ferns or most other shade tolerating plants won't have any negative effects on established trees and shrubs. As long as the ferns have enough space to leaf out and aren't completely swamped they can be planted as densely as you see fit.

Far too many gardens have individual plants surrounded by lots of brown dead space. I don't know if it's supposed to look tidy or something, much better to have a thriving, living oasis.

Reckless Abandonment

Alot depends on the type of rose. But especially the conifer . Do you know what it is. Im a big fan of planting everything close, doesn't always work but its all trial and error . Roses can usually have other plants under them conifers can be a different story.