Panicum virgatum 'Heavy Metal' is a dramatic switch grass forming vertical pillars of metallic blue.

Passiflora caerulea is one of the hardiest of passionflowers with blue, black and white flowers.

Passiflora 'Alba' is a pure white form of the hardy blue passion flower.

Passiflora 'Clear Sky' has greater vigour and larger flowers with greater substance.

This is our selection of the hardy blue passionflower, Passiflora caerulea, with larger flowers with bluer blues and blacker blacks!

The hardiest of all passionflowers, Passiflora incarnata 'BluePop' has ornate bluish flowers and tasty fruit.

Passiflora 'Betty Myles Young' offers exquisitely detailed, large, lightly scented passionflowers.

Passiflora 'Silly Cow'/'Damsel's Delight' has dark purple filaments against pale lilac petals. Gorgeous.

True blue spikes of tubular flowers.

Penstemon barbatus Riding Hood 'Delft Blue' has deep blue, tubular flowers with purple infusions on slender stems.

Penstemon caespitosus 'Wagon Wheel' is a ground hugging perennial with stems that grow into circular mats of small blue flowers.

'Margarita BOP' is a strong, winter hardy Penstemon with tubular flowers in shades of blue and purple produced in masses all summer long.

Penstemon linarioides var. coloradoensis 'Silverton' forms evergreen, silvery mounds topped with spikes of blue, purple, and pink tubular flowers.

Penstemon strictus is a tall, dramatic species to about 30 inches with bold blue and purple tubular flowers.

Penstemon 'Cha Cha Lavender' offers tubular lavender purple and white flowers all summer long.

Perovskia atriplicifolia 'Blue Steel' has some of the darkest blue flowers of the Russian sages.

Perovskia 'Denim 'n' Lace' is a dwarf cultivar of Russian sage with silvery foliage and purple-blue flowers.

Perovskia 'Lacey Blue' is a dwarf cultivar of Russian sage with the classic silver-green foliage and purple-blue flowers.

Perovskia 'Silvery Blue' is a dwarf cultivar of Russian sage with extra silver foliage and purple-blue flowers.

Phlox divaricata 'Blue Moon' is an eastern North American native ground cover with fragrant, pale blue flowers.

Phlox divaricata 'Blue Ribbons' is a woodland ground cover with fragrant lavender-blue flowers and variegated foliage.