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10 May 2021

How to grow hardy geraniums

Adaptable, dependable and colourful, hardy geraniums deserve their popularity. Discover our best geranium varieties and tips for how to grow them.
Hardy geranium
CT
Ceri Thomas

They’re surprisingly tough and very diverse, with varieties for almost every situation in the garden. Although many of them love the sun, plenty of varieties are said to be happy in shade, including tricky dry, shady areas.

Which? Gardening magazine grew a range of popular varieties to see which would give us the best display.

How to grow hardy geraniums: month by month

January February March April May June




PLANT PLANT FLOWERING FLOWERING
July August September October November December
FLOWERING/CUT BACK









Best hardy geranium varieties

Which? members can log in now to see the full results and which are our Best Buy varieties. If you’re not a member, join Which? to get instant access.

Best Buy hardy geraniums for sun
What it looks like Variety name Height x spread
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40 x 90cm
With small magenta flowers typical of many hardy geraniums, ‘this variety might not set pulses racing, but it has plenty to recommend it. The neat mounds were densely covered with small lobed leaves and plenty of bright blooms. It got going in June in north London and early July in Glasgow, then flowered well right through into October. It attracted plenty of bees, too, especially later in the season when fewer other flowers were out. Peak flowering:  June-October (July-October in Scotland).

What it looks like Variety name Height x spread
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40 x 70cm
The flowers of this variety were showy enough to compete with the more striking varieties, yet still subtle enough to work well in a cottage-garden setting. The dainty dissected foliage was also pretty, with a deep-green colour that made a good backdrop to the vibrant blooms. It didn’t produce masses of flowers, and tailed off a bit after midsummer – but it kept going well enough to be attractive into autumn, when the leaves turned red. Peak flowering: May-July.

What it looks like Variety name Height x spread
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55 x 135cm
Our plants of this variety were amazingly vigorous, especially in north London. They spread over a huge distance and flowered non-stop all summer, bees feeding on them all the while. In Glasgow, on heavier soil, they were less vigorous – which might be a good thing if your garden is small – but still carried plenty of sweetie-pink flowers, especially later in the summer. They also kept a good clump of leaves over winter in both locations.

What it looks like Variety name Height x spread
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30 x 80cm
This was one of the last varieties to come into flower in our trial – and we were beginning to wonder how it had won the accolade. Once it got going, however, it redeemed itself with a show of big, perky flowers, held well above the leaves, which also had great impact. Our plants carried on blooming steadily until autumn at both trial gardens. Peak flowering: July-October.



What it looks like Variety name Height x spread
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40 x 90cm
One of the newer introductions, this variety is a real delight. Its mounds of delicate brown leaves were dotted with cherry-pink flowers for the whole summer. The mounds grew constantly, so we chopped away some of the older stems in late summer. Bred in the Orkney isles, this geranium is said to be very hardy and was evergreen in both locations. We thought it would look great trailing over the sides of a pot or down a wall. Peak flowering: May-September (June-September in Scotland).



What it looks like Variety name Height x spread
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75 x 110cm
A relatively recent introduction, this variety was taller than expected and very vigorous at both trial gardens, so would need a bit of room around it. It was long-flowering, too, with terrific impact from the vivid purple-blue flowers and lacy foliage. As the season progressed, the stems began to splay outwards and look less fetching. So we chopped them back, let the central clump of fresh leaves take over, and got a second flush of flowers in September.





Best Buy hardy geraniums for shade
What it looks like Variety name Height x spread
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25 x 70cm
The dainty, dark-green leaves were one of the chief attractions of this lovely geranium, but the deep-pink flowers with washed-out edges really brought it to life. In our previous trial, we grew it in full sun and it performed so well, we made it a Best Buy. In this trial, we grew it in dry shade. And although we don’t think it bore as many blooms this time, it still grew and flowered very well, so it’s an adaptable variety. Peak flowering: May-July
What it looks like Variety name Height x spread
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40 x 75cm
For a simple solution to the problem of dry shade, this pretty variety is a great choice. The plants formed lovely dense mounds and had fresh green, felty leaves. The small white flowers were held on short stems among and just above the foliage, and stood out really well against this soft backdrop. The plants flourished in both trial gardens, but were particularly impressive in a very dry part of the bed in north London. Peak flowering: June-July
What it looks like Variety name Height x spread
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30 x 65cm
The finely dissected, dark-green leaves were one of the best things about this variety. The low-growing mounds were bushy and covered in vibrant pink flowers with faint red veins. They were also happy in a dry part of the bed and put on a strong display in early and mid-summer, followed by a smattering of flowers that kept the display going until the end of August. Peak flowering: May-July
What it looks like Variety name Height x spread
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45 x 90cm
A Best Buy from our previous trial, when it was grown in full sun, this variety did just as well in the shade in this trial. We planted it in the more moist parts of the beds at both trial sites, and it grew strongly, forming dense and spreading mounds of soft, mottled, green leaves. The large, distinctive flowers opened later than most varieties, but then they kept blooming well into autumn. This was the case in our trial garden in Scotland, as well as in north London. Peak flowering: July-October


How we test hardy geraniums

We chose a range of geraniums and grew three plants of each variety in our trial gardens at Capel Manor, north London, and at Oatridge College in West Lothian, Scotland. After planting, we watered the plants until they were established, then left them to cope with any dry spells. For all varieties where the first flush of flowering ended in early summer, the stems were cutback to encourage a second flush of flowers. All the plants were grown for two years and assessed for how many flowers they, how long they lasted and how good they looked; how attractive the foliage of the plant was; how dense and attractive the form was; whether the plants were diseased or particularly prone to damage from pests; and how many bees visited the flowers.

Caring for your plants

Planting

Geraniums can be planted at any time of year, as long as the ground isn’t frozen. However, the widest selection of varieties will be available to buy in spring.

Plant in well-drained soil. Water them well after planting. Even the plants suited to dry soil will benefit from being watered until they’re established and growing well.

Pruning 

When the first flush of flowers finishes, cut the plants back hard. Fresh leaves will soon grow and you might get a second flush of flowers.

Tidy up the plants in spring by removing any dead growth from the previous year.

Dividing

If clumps grow too big, they can be divided in spring. This can be done every few years if needed. Dig up the clump and either cut it into sections or divide it with two forks, pushed through back-to-back.

Common growing problems

Powdery mildew

Powdery mildew appears as a white down on the leaves. Improving air flow and watering the plants can help to alleviate it.

Read more about powdery mildew

Rust

Rust appears as brown pustules on the leaves. Remove any affected leaves as soon as you see signs, or spray with a suitable fungicide.

Vine weevils

Vine weevil grubs like geranium roots. If plants look wilted but don’t recover after watering, check how firmly they’re anchored in the soil and look for the white, ‘C’-shaped grubs. Use nematodes to treat the problem and apply while the soil is still warm enough in late summer.

Read more about vine weevils