• Let color unify the gardens. "I'll pick one dominant color ― red, orange, dark purple, gold ― then use that with liberal amounts of dark green and lime green foliage," Will Green explains. Lime and chartreuse also add light to the garden.
• Use hedges as garden walls. Vine-covered lath panels also work to create a sense of enclosure. Don't let your garden rooms get too small, though; 12 by 20 feet is a good minimum size.
• Provide for flow between rooms. Connect various paths to create a route through the separate garden rooms. Provide each one with an entrance and an exit; they do not have to be opposite each other.
• Create views. Locate seating away from the garden's perimeters so there's something to look at ― whether a great container or wall fountain, or a peekaboo view ― on all four sides.
• Hang a mirror. It'll reflect light and create the illusion of infinite space. In Green's checkerboard courtyard, an eye-level mirror is framed with vines that dangle just enough to keep birds from flying into it.