We tend to associate green in the garden with foliage, but there are flowers that supply that same color. They can be combined to great effect with dark-leaved plants, or those with variegated foliage. Here are some of our favorite options:
Hellebores: Among the hundreds of hybrid hellebores on the market, you'll be able to find some green-flowered options, such as 'Green Gambler' and Helleborus argutifolius 'Sliver Lace', with beautiful silver-flocked leaves and large creamy green flowers (USDA Zones 4–9). Or look for the species H. foetidus, called the stinking hellebore. It has light green blossoms and blue-green leaves (Zones 5–9).
Zinnias: Try 'Green Envy' or 'Benary's Giant Lime' for lush green flowers. Zinnias are annuals typically grown in full sun, but some gardeners report better color from the green selections if they are kept in part shade.
Flowering tobacco: Nicotiana alata 'Lime Green' is a three-foot, bushy perennial in USDA Zones 8–10, grown as an annual elsewhere. It often self-sows. It blooms for a long time, with trumpet-shaped chartreuse flowers. The species Nicotiana langsdorffii has a similar size but its pale green flowers are more drooping. For a compact flowering tobacco, try N. a. 'Starmaker Deep Lime', which grows just a foot tall and bears outward-facing, two-inch flowers.
Coneflowers: Purple coneflower (Echinacea purpurea; Zones 4–9) can be found in a rainbow of colors, and green is not lacking. 'Green Envy' has mostly light green petals; toward the center of the flower they turn pinkish red, and the central cone is dark green. There's also 'Green Jewel', which is solid in color, or the bicolor 'Sweet Sandia', which combines lime green and watermelon pink.
Hydrangea: For a green-flowered shrub, there's the six- to eight-foot panicle hydrangea Hydrangea paniculata 'Limelight' (Zones 3–8), which has soft lime green flowers in late summer. Several mophead cultivars of smooth hydrangea (H. arborescens; Zones 3–8) also bloom green, including Lime Rickey and Invincibelle Limetta.
Bells of Ireland: The true flowers of Molucella laevis, a cottage-garden classic, are actually white; they are tiny and surrounded by the large green calyces that inspire its common name. This annual grows best in cool weather. Its seeds can be sown outdoors in early spring.
Photo credits: Stinking hellebore by F. D. Richards/CC BY-SA 2.0; Zinnia by Carmen Castells Schofield/CC BY 2.0; 'Starmaker Deep Lime' tobacco by Cultivar413/CC BY 2.0; 'Sweet Sandia' coneflower courtesy of Terra Nova Nurseries, Inc.; Bells of Ireland by Dwight Sipler/CC BY 2.0