Hardy geraniums are the most popular perennials in Britain. And it’s easy to see why. They’re tough and easy to grow, many flowering for months at a stretch.
What’s the difference between a geranium and a pelagonium? Most people call pelargoniums “geraniums.” But Geranium is actually a different plant genus. To help avoid confusion some refer to Geranium as ‘hardy geraniums’, and Pelargonium as ‘tender geraniums’. These 10 hardy geraniums have won the RHS Award of Garden Merit (AGM). They are perfect for your garden.
When it comes to hardy geraniums, two of the most popular varieties are ‘Johnson’s Blue’ and ‘Rozanne’. Both offer stunning purple-blue blooms and easy care but there are some key differences between these two plants that are worth considering when making your choice.
An Overview of ‘Johnson’s Blue’ and ‘Rozanne’
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‘Johnson’s Blue’ is a classic cottage garden plant, valued for its prolific flowering in early summer. First introduced in the 1940s, it forms a compact mound to around 12-18 inches tall and wide, with cup-shaped flowers in a rich violet-blue shade with white centers.
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‘Rozanne’ is a newer variety, introduced in 2000. It is taller, reaching 18-24 inches tall and wide. The flowers are a similar violet-blue but have a more open form with ruffled petals. ‘Rozanne’ blooms for an exceptionally long period, from early summer until first frost.
Both are exceptionally hardy, coping well in zones 4-8 and requiring minimal care once established. They prefer full sun to part shade and average, well-drained soil.
Flowering Time and Abundance
One of the biggest differences between these two geraniums is their flowering performance over the season.
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‘Johnson’s Blue’ blooms vigorously for 3-4 weeks in early summer. Flowering starts in early June peaks in mid June with abundant blooms and winds down in early July. The flowers are produced in clusters, completely coating the foliage in rich color.
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‘Rozanne’ has a much longer flowering window from early summer to fall However, it does not flower with the same intensity as ‘Johnson’s Blue’ at peak bloom. The flowers are produced steadily but not abundantly Often just single blooms appear sporadically amongst the foliage from July through October.
So while ‘Rozanne’ offers months of color, ‘Johnson’s Blue’ makes more of an impact at its peak bloom time. If you’re looking for a bold floral display for 3-4 weeks in early summer, ‘Johnson’s Blue’ is the better choice. For continued color all season long, opt for ‘Rozanne’.
Growth Habit and Foliage
In terms of their growth habit, ‘Rozanne’ is taller and more sprawling than the compact, mounding ‘Johnson’s Blue’.
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‘Johnson’s Blue’ forms a tidy clump at around 18 inches tall and wide. Its leaves are medium green and lightly textured.
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‘Rozanne’ can reach 24 inches tall and 36 inches wide. It has a more open, spreading habit and larger leaves with bolder veining and a slight chartreuse marbling.
The lower, spreading growth of ‘Rozanne’ gives it a floppy tendency, so it benefits from cutting back after flowering to improve its shape. ‘Johnson’s Blue’ holds its form well all season.
Hardiness and Care Requirements
Both ‘Johnson’s Blue’ and ‘Rozanne’ are very hardy and easy care in the garden. They have similar needs:
- Full sun to part shade
- Average, well-drained soil
- Moderate watering, avoiding wet feet
- Cut back after flowering to promote new growth
- Divide congested plants every 3-5 years in spring
‘Rozanne’ appreciates a bit more sun to flower her best. ‘Johnson’s Blue’ is a little more shade tolerant.
Over time, both may become prone to fungal leaf spots. Good airflow and pruning helps prevent this. Overall, they are unfussy, tough plants. ‘Johnson’s Blue’ is a slightly easier care variety.
Uses in the Garden
These geraniums have different habits, so they work well for different garden uses:
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‘Johnson’s Blue’ is ideal for the front of borders, edging paths and walkways, and containers. It forms a perfect compact, mounding shape.
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‘Rozanne’ can be used in borders but shines spilling over walls, tumbling down slopes, and softening steps and retaining walls with its spreading form.
In Summary
- For prolific color in early summer, choose ‘Johnson’s Blue’
- For long blooming from early summer to fall, ‘Rozanne’ is best
- ‘Johnson’s Blue’ has a tidier habit, ‘Rozanne’ is more spreading
- Both are very hardy and easy to grow
- ‘Johnson’s Blue’ works well in beds and containers, ‘Rozanne’ is ideal for slopes and walls
When chosen for their different strengths, both ‘Johnson’s Blue’ and ‘Rozanne’ make fantastic additions to gardens. Their long flowering, vivid color, and easy care make them ideal for any garden setting. Whether you favor one over the other comes down to the look you wish to achieve and your personal preference.
The ideal ground cover
You could say that Geranium ‘Orion’ is like the old Geranium johnsonii ‘Johnson’s Blue’, but much, much better. It is one of the best new hardy geraniums. Large blue flowers with lavender tints and purple veins open in huge numbers all summer long, making a great ground cover. The broad petals overlap to create bowl-shaped flowers and the white centres accentuate the colouring. A seedling of Geranium ‘Brookside’, another fine AGM winner. 75cm (30in). Hardiness rating H7.
Geranium ‘Mavis Simpson’ is a low and spreading, almost evergreen plant. It has silvery leaves with lobes that look beautiful against the pink flowers that have a silvery top and dark veins running through them. From June to October, flowers bloom, and the stems spread out a lot, but they’re easy to cut back because they don’t grow roots. Found as a chance seedling at Kew, and named after a Kew gardener. 20cm (8in). Hardiness rating H6.
The flowering ground cover grows quickly, spreads out wide, and blooms for a very long time. The magenta pink flowers with purple veins open in July and stay open until a hard frost. Geranium ‘Dilys’ doesn’t like it when it’s dry, but it’s useful because it can handle poor drainage and does well in both full sun and part shade. Named in honour of Dilys Davies, for many years an influential member of the Hardy Plant Society. 40cm (16in). Hardiness rating H7.
Purple veins, purple veins
Geranium Rozanne (‘Gerwat’) is a stupendous plant making vigorous ground cover or a dramatic container specimen. From July to October, a lot of saucer-shaped flowers bloom with purple veins and a bright white center. They are set against fresh green leaves. It needs a lot of room or looks great planted as a single plant in a big pot, where it makes a blue waterfall of color. ‘Jolly Bee’ has now been pronounced as identical. 60cm (2ft). Hardiness rating H7.
Geranium renardii has some of the most beautiful leaves of all hardy geraniums. Each broad, lobed, grayish leaf has the soft feel of sage leaves. In June and July, sprays of white flowers with deep purple veins grow just above the leafy mound. This plant stays small and slowly spreads, making it perfect for the front of a sunny border. The leaves look their best when they are dry. 35cm (14in). Hardiness rating H6.
This form of our native Geranium pratense (meadow cranesbill) has delicate patterns that look good both up close, where you can admire the rich colors, and far away, where the haze of color stands out. Geranium pratense ‘Mrs. Kendall Clark’ has pale blue flowers that open in June and July. The flowers have a network of white veins, and they will bloom again if you cut off the dead flowers. In spring, the mound of new lobed foliage is also attractive. 90cm (3ft). Hardiness rating H7.
Many varieties of this widely grown
A hybrid plant is the offspring produced by cross-pollinating one specific cultivar with another different cultivar. Cross-pollination, as opposed to pollination between plants of the same cultivar, usually makes offspring that are stronger, healthier, and better. These offspring are called “hybrid vigour.”
Geranium Rozanne: 6 Reasons to Plant This Special Long Blooming Perennial
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