Beth Chatto taught it to me in her terrific book titled "A Green Tapestry"..................
"I do not aim for a showy display of unseasonal plants in flower but tend to concentrate on the effect of contrasting shapes, sizes and designs of leaves."
and
"I cannot emphasize enough that the form and shape of the plant and the texture and color of its leaves are as important as the color of its flowers. Leaves have a much longer-lasting effect than flowers................"