For non-stop summer flowering geraniums, three hardy varieties immediately spring to mind - ‘Orion’, ‘Patricia’ and ‘Rozanne’. However, as they form large plants that billow out, all three need space to shine as they can cover a yard, almost a metre, of ground.
‘Orion’ (a seedling from ‘Brookside’ discovered by Dutch nurseryman Brian Kabbes in the 1990s) is a stunning deep-blue that begins to flower in early May. Masses of large dark-veined flowers are held on long stems almost smothering the divided green foliage. ‘Orion’ emerged as the best deep-blue on the extensive hardy geranium trial held at RHS Wisley between 2005-2007.
‘Rozanne’ (discovered in 1990 in Rozanna Waterer’s Somerset Garden) is a softer blue that flowers later, sprawling over the ground. At RHS Wisley ‘Rozanne’ (syn. ‘Jolly Bee’) is given the Chelsea chop (ie cut back hard in the third week of May) to delay flowering until August.
‘Patricia’, bred by Orknet-based specialist Alan Bremner, is a striking dark-eyed magenta.
Geranium flower power
All varieties above are sterile, so won’t set seed, and this is the secret of their non-stop flower power.
Sterile hybrid geraniums make excellent garden plants because they have hybrid vigour and, although they are popular with bees, their flowers never set seed. This means that the flowers last much longer and this is true of all sterile plants.
Many of these hybrids arose as spontaneous seedlings and were spotted by sharp-eyed nurserymen who recognized a difference in flower or foliage. Usually they are crosses between closely-related species and a chromosome incompatibility produces sterile offspring.
Deliberate hybridisation (with a brush) is usually very difficult although Alan Bremner has managed to raise several types. They include ‘Patricia’ AGM, ‘Anne Thomson’ AGM, ‘Dilys’ AGM and ‘Joy’. All these genarniums make excellent garden plants, although I find ‘Dilys’ and ‘Joy’ need good drainage.
Geranium growing advice
Most of the larger sterile geraniums are easy to grow, very hardy and their saucers add much to the border. When the plant begins to look ragged, typically after a couple of months, it’s possible to chop it back hard.
Hardy geraniums respond within days, sending out new leaves and then flowering four weeks later. This makes them versatile and useful with roses, peonies and other herbaceous plants.
Larger clump-forming geraniums can be divided as they break into growth. Simply chop up the clumps using a spade and replant chunks straight back into the ground, keeping them well watered. Smaller divisions can be potted up and replanted in September.
Smaller non-stop hardy geraniums
There are some smaller, non-stop sterile hardy geraniums, but they are generally plants for full sun and good drainage because they often involve grey-leaved, borderline-hardy species like G. traversii.
Find a hot spot or place it on a scree slope or rockery. Be prepared to divide every second year to raise new plants: once the mature plants begin to look gappy they succumb to winter weather.
Pull small pieces plus some stem away in June and July and root them in 100% coarse horticultural sand or a 50% mixture of coarse sand and compost.
Pot up once rooted and plant outside in the following spring, making sure that potted plants waiting to be planted avoid winter wet.
Geranium x riversleaianum ‘Russell Prichard’ AGM
This cross between G. traversii and G. endressi (or possibly G. sanguineum) first arose at Prichard’s Riverslea Nursery near Christchurch in Hampshire - hence the rather clumsy species name. It has magenta-pink flowers with red veins and is less said to be less hardy than ‘Mavis Simpson’, but it has been around since the 1930s at least. Propagate regularly.
Geranium x riversleaianum ‘Mavis Simpson’ AGM
One of the prettiest pale-pink geraniums with silver-grey foliage. Found at Kew in 1982 and named after the gardener who spotted it. Wonderful with silvered eryngiums or pale-blue nepeta.
Ten first-rate hardy geraniums for the garden
G. cinereum ‘Ballerina’ AGM
For a rock garden, scree of sunny hot spot. This dark-eyed pale-pink hardy geranium has dark veins and flowers held above a cushion of foliage. Alan Bloom 1962. Forms a tight clump and flowers for many weeks (6 ins/15cm).
G. cinereum ‘Purple Pillow’
Burgundy-red to magenta and very floriferous - a low growing variety for a hot spot (6 ins/15cm).
G. clarkei ‘Kashmir White’ AGM
Large, magenta-veined white flowers on an airy plant. Flowers in early summer (just once) but is excellent with pink, magenta or purple roses. Also performs in shade (2ft/60 cm).
G. phaeum ‘Rose Madder’
A phaeum-like spring-flowering geranium for dappled shape. Very pretty brown-pink flowers when grown in the right position (30 inches/75 cm).
Green scalloped leaves topped by gappy violet-blue flowers. The soft foliage is very pretty so the fact that it flowers once shouldn’t put you off (15 ins/35cm).
G.pratense ‘Mrs Kendall Clark’ AG
Pale-lilac flowers veined in grey-white on this upright midsummer-flowering meadow cranesbill. Sets lots of brown seeds - so dead head if this bothers you. Comes true from seed. There are double sterile forms with pom-pom flowers like the violet-blue 'Plenum Violaceum' AGM and a splashed blue and white form with a jumping gene correctly called ‘Striatum’ (3ft/90cm).
From Crug Farm Plants in North Wales, ‘Sue Crug’ is a dusky pink with dark staining - although hardiness may be a problem (1ft/30 cm).
Finely-cut foliage and masses of violet-blue starry flowers over many weeks make this a light, frothy hardy geranium that shimmers in sun, or dappled shade. Found at the Cambridge Botanic Garden and introduced by Axeltree Nursery in 1990.
Glossy foliage and pink-purple flowers without a dark eye make this a stunning plant. The middle of the flower looks silvered in sun. Honours are shared between Hans Simon of Germany and Alan Bremner - both raisers of fine geraniums who each bred this identical hybrid.
Geranium sanguineum ‘Album’ AGM
This low-growing geranium tolerates really dry conditions. Dark-green divided foliage and clean-white flowers make it look cool and fresh. Arose in a Scottish garden.