Geranium ‘Johnson’s Blue’ and Geranium ‘Rozanne’ (cranesbill) have beautiful blue iridescent flowers. My hardy geraniums are flowering in a part shade bed, where their colour brightens the garden. I appreciate the long sequence of blooms in summer and into fall.
The flowers of these geraniums are often described as blue, but compared to the blue of the lobelia across the path, the petals are leaning towards purplish blue. It’s a lovely colour in the garden, with a shimmery sheen when it catches the light.
Geranium Johnson’s Blue has many of these five lobed blooms with shimmery threads running through the petals. These give the flowers a slight iridescent appearance. The petals are a little more blue than Rozanne, which leans more towards purplish blue. The flower of my Johnson’s Blue started blooming 9 days before Rozanne, but Rozanne was new last year, so that might still be affecting the natural bloom time.
The plants of Johnson’s Blue sprawl a bit more than Rozanne. Mine are about 45 cm (1.5 ft) tall and a little wider. They have a loose structure, and suit a cottage garden style, or being placed next to plants that they can mingle with at the edges. I have mine under a lilac, and they share the space beautifully. There is a tall Aruncus (goatsbeard) perennial to one side, that doesn’t mind the odd blue flower resting on it.
Geranium Rozanne has a gorgeous purplish blue colour. Like Johnson’s Blue, each flower has a white centre, but the white centre is larger on these flowers. The blooms themselves are a little larger too, and the individual petals of Rozanne are wider, overlapping more than Johnson’s Blue.
The foliage of Rozanne is a lighter green colour than Johnson’s Blue. There is a faint marbling effect to the leaves on this perennial. Mine are a little shorter than than Johnson’s Blue, with the foliage closer to 30 cm (12 in) tall.
The hybrid name for Rozanne is actually Geranium ‘Gerwat’, but I haven’t seen it sold under that name around here, not even as fine print on a label. I’ve seen Rozanne generally rated for a warmer area than zone 3, but all eight of my plants overwintered fine, and last year had typical temperatures. They just had a bit of leaf mulch that blew over for protection, but seem perfectly hardy. Mine are in a somewhat protected suburban garden, so the wide open zone 3 prairie might be different.
Here’s a Rozanne flower on the left, and a Johnson’s Blue on the right for comparison. If you are looking for an informal perennial for the part shade, both of these hardy geraniums are super additions to the garden. Give them some neighbours that don’t mind mingling at the edges. They also look great next to a path, especially if you are looking for a plant to soften the edges as they spill over.
Here is a post showing pictures of the pretty blue Geranium ‘Rozanne’ planted with the lavender blue flowers of Campanula lactiflora (milky bellflower) in my garden.