Smoke bush: Purple smoke bush makes a great moody backdrop for billows of 'Monch' blue aster, or for sulphur-yellow 'Moonbeam' coreopsis. You can clip it low, to stay an accent piece in a smaller-scale garden, or you can prune off the bottom branches and train it into a graceful tree. Or slice it off at ground level in spring before budding and it'll send up poker-straight new shoots that look great with June perennials. Smoke bush's foliage turns muddy brown by late summer, but all is forgiven when it flames into a burst of orange and red for fall.
Photo: (cc) mark wordy/flickr
Shrubs: I use Physocarpus 'Diabolo', Weigela 'Wine and Roses', and Sambucus 'Black Beauty' to complement the perennials and to help tie the garden together. My favorites all grow well in my zone and do not require spraying, extra fertilizer, or staking. Plants that need the "intensive care unit" to survive do not make for a sustainable garden.
—Stephanie Cohen, coauthor of the Perennial Gardener's Design Primer (Storey Publishing, 2005)
Photo: (cc) redcaz22/flickr
Mondo grass: I have a much-loved, incredibly slow-growing black mondo grass in an old Japanese pot—it's a great container plant.
Photo: (cc) brewbooks/flickr
—Lauren Springer Ogden
Vegetables: I would grow some of my favorite black vegetables for their magnificent color alone. The tomatoes 'Black Cherry', 'Black Plum', and 'Black' are stunning on a plate. The color of the ornamental peppers 'Purple Delight' and 'Royal Black' is a saturated ultramarine violet. And the pumpkins 'Futsu' and 'Yokohama' are gorgeous traditional Japanese varieties.
—Amy Goldman, author of The Compleat Squash (Artisan, 2004)
Keep Reading: 7 Secrets for a High-Yield Vegetable Garden
Photo: (cc) Matevz Umbreht/flickr