Acaena inermis 'Purpurea' is an excellent ground cover for crawling over gravel paths or stones with gorgeous purple-blue-grey foliage.

Acaena saccaticupula 'Blue Haze' is an excellent ground cover with powder blue foliage.

Achillea millefolium, the common yarrow, is an important nectar source and host plant for a diversity of insects.

Agapanthus 'Galaxy Blue' has large umbels of royal blue, trumpet-shaped blossoms. Hardy to zone 6!

Agapanthus 'Galaxy White' has five inch wide umbels of white, trumpet-shaped blossoms on tall stems. Hardy to zone 6!

Agapanthus 'Poppin' Purple' is a compact, fast-growing lily-of-the-Nile with violet purple flowers.

Agapanthus 'Summer Love Blue' has fragrant violet-blue flowers on strong green stems and green, strap-like foliage.

Among the best of the blue Agastache, 'Black Adder' has blue flowers and deep purple blue bracts for a bicolour effect.

Agastache 'Blue Bayou' is a long-blooming hummingbird mint with blue tubular flowers and aromatic foliage.

Hot sunny spots will never be the same with long-blooming Agastache 'Blue Boa'. Butterflies and bees will love you!

'Crazy Fortune' is a sport of Agastache 'Blue Fortune' with lavender blue flowers and variegated foliage.

Agastache 'Danish Delight' is an anise hyssop with vibrant hot pink to reddish-purple blooms and fragrant green foliage.

Agastache 'Mango Tango' is a compact, long-blooming hummingbird mint with dusky rose and peachy orange flowers.

Agastache 'Morello' is a dramatic hummingbird mint with huge, dense infloresences of deep burgundy rose flowers.

Agastache 'Pink Pearl' is a stunning hummingbird mint with dense spikes of mid pink buds opening to glowing light pink flowers.

Agastache Meant to Bee 'Queen Nectarine' has soft peach flowers with mauve calyxes on tall three foot stems.

Agastache 'Rosie Posie' is a compact cultivar with two-tone, magenta and pink flowers that will bloom all summer and attract pollinators.

Agastache 'Royal Raspberry' is a long-blooming hummingbird mint with fragrant purple tubular flowers and aromatic foliage.

Agastache 'Tango' is a dwarf cultivar with big flower power in firey orange for containers or the front of the border.

Agastache Kudos 'Red' hummingbird mint has bright true red flowers atop aromatic foliage for months in the sunny garden.

Agave 'Little Penguins' is a cute dwarf century plant with many linear, bluish leaves each tipped with a prominent black spine.

'Mr Ripple' is a fantastic agave with wide, blue-green undulating leaves.

Agave bracteosa 'Calamar' looks more marine-like than plant-like with long, narrow, notably spineless, bluish to apple green leaves.

Agave chrysantha has long, narrow, bluish leaves with bold marginal spines. The flowers are bright yellow.

Agave deserti var. simplex is a small to medium-sized century plant with silver-blue leaves.

Agave havardiana is a very cold hardy cactus to zone 5 with broad, impressive bluish leaves forming impressive rosettes.

Agave ovatofilia 'Frosty Blue' is a cold hardy century plant with blue-green foliage also known as whale's tongue agave.

Agave 'J.C. Raultston' has a particularly beautiful form of wide, bluish grey, succulent leaves and greater tolerance of wet winters.

Agave parryi var. huachucensis is a dramatic form with bluish-grey succulent leaves held in tight artichoke-like rosettes.

Agave parryi var. truncata is a dramatic, bluish-grey succulent with tight artichoke-like rosettes and shorter leaves than other forms.