PERENNIALS > GERANIUMS
IN THIS GUIDE
The virtues of Hardy Geraniums are too numerous to reel off but suffice it to say that there must be solid reasons for these plants to be the United Kingdom’s favourite perennials.
Very many varieties are prolific and bloom for months on end, and the simple flowers exude a genuine charm all their own with their differing and delicate venations lending blooms a graceful refinement.
The Geranium genus has a vast habitat that spans all climatic zones, yet this remarkable range is exceeded by the popularity of this plant. And for good reasons: a majority of varieties are perennial, as many are hardy, a large number bloom all summer long, they are so easy to grow, and they boast truly delightful flowers!
Geraniums belong to Family Geraniaceae as do the closely-related Pelargoniums. Originally the species of both genera were classed together in Genus Geranium. Although they were separated and reclassified into genera Geranium and Pelargonium over two centuries ago, plants of the latter genus are sometimes still considered and called Geraniums. As a result, to differentiate between the two, Geraniums proper are often called ‘Hardy Geraniums’ or ‘True Geraniums.’ This article does not cover Pelargoniums.
|Official Plant Name||Geranium|
|Plant Type||Perennial / Annual Flower|
|Flowers||Rounded, 5 petalled flowers in various hues|
|When To Sow||January, February, November, December|
|Flowering Months||June, July, August, September|
|Deadhead And Trim||July, August|
|When To Prune||September, October|
Full shade or partial shade, some even in deep shade
Exposed or Sheltered
0.5 – 1M
0.5 – 1M
June – September
Most Soil Types
Moist but well drained
The Geranium genus includes 400 to 420 species and over 800 cultivars with almost all the in-demand varieties being perennials. These plants are also called Cranesbills because the seed capsule of many species brings to mind a crane’s bill. These capsules exhibit one of the more interesting and dynamic Botanical mechanisms related to seed dispersion. When the seeds within a capsule are mature, the capsule bursts open and throws out the seeds. Geraniums also possess other traits that are exciting, especially for hobbyist gardeners.
Exceptional Properties of Geraniums
First, though Geraniums themselves are very easy to grow and care for, many varieties make life tough for weeds, tending to stifle them! Next, the habits and forms of the 1200-plus varieties cover the gamut of mat-forming, creeping, mounding, clumping, bushy, spreading, erect, and upright; naturally, therefore, varieties’ heights range from a mere 12 centimetres to well over a full metre. Finally, a thumping 57 varieties have been awarded the Royal Horticultural Society’s Award of Garden Merit.
The visual appeal of these plants begin with the foliage. Be the leaves a medium or dark shade of green, the colour is almost always rich and deep with some having a shiny lamina. What is more, come autumn, many varieties’ leaves become tinged with red, bronze, or golden-yellow or even change colour entirely. The leaves also have a pretty shape, being oval to round, and palmately lobed, often deeply.
As it happens, in a show of sympathy and artistic symmetry with the lobed leaves, many Geranium flowers’ petals are notched at the distal borders, some quite deeply. The lovely five-petalled flowers are bowl-shaped, salver-shaped, or flatly disk-shaped. Their colours fall in the red to blue spectrum with the hue ranging from very pale to vibrantly intense, from a pinkish-white to brilliant violet. A feature typical of Geranium flowers is the well-known delicate radial veining along the petals. To cap off their attractions, a majority of Geraniums draw bees and butterflies.
Geraniums are one of the most popular plants for beds and borders but they also make wonderful container plants for the windowsill and balcony. Considering that a majority produce blooms for the whole summer with a significant number extending their flowering season deep into autumn, with other varieties getting the show underway sometime in spring, it is no wonder that Geraniums are the United Kingdom’s favourite perennial plants.
Background and Origins
Though one often reads that Cranesbill Geraniums are native to the world’s temperate zones, this is hardly the whole story. Many species are native to subtropical zones and some even grow in the tropics albeit in highland and montane regions. For example, countries such as Zaire, Thailand, and Colombia are host to Geranium species. In fact, Geraniums are absent from only a handful of countries.
Geraniums are found in their highest concentration and greatest diversity in Greece and the Mediterranean region. Indeed, evidently the Greeks foreran the British by centuries in observing the resemblance between these plants’ seed capsules and cranes’ beaks because ‘geranos’ is the Greek word for crane!
Several Geranium species, for example G. pratense and G. pyrenaicum, are endemic to the British Isles. To this native stock, Mediterannean and European species began to be added from the late Sixteenth Century onwards. However, Geranium cultivation proceeded at what may be described as a leisurely and dignified pace for four centuries until the 1970s and 1980s when RHS trials and a couple of fine books brought about an explosion of interest, leading to intense horticultural activity and the development of some spectacular cultivars.
Why not open our run-through of selected varieties with one of the most renowned and most-desired varieties of any plant, G. ‘Gerwat’ or G. [Rozanne] or ROZANNE, called ‘G. Rozanne’ in North America. A winner of awards on both sides of the Atlantic, it is a recipient of the RHS’s Award of Garden Merit. Getting on the shortlist for the RHS Plant of the Centenary at the Chelsea Flower Show for the decade 1993-2002, it was the outright winner of the public vote. It was also the Perennial Plant Association’s Plant of the Year for 2008. Even by exalted Geranium Standards Rozanne is a vigorous and trouble-free variety and is known as a prolific bloomer over an unusually long flowering season that begins in spring and continues through autumn. It has a matching height and spread of 50 to 60 centimetres. The remarkably pretty 5-centimetre flowers have a whitish centre, and purple venation running through true violet petals.
G. robertianum or Herb Robert is known by numerous colloquial names. It is a very important species in Naturopathy and is native to the British Isles. The leaves are unusual in being so heavily dissected as to be palmate. The small disk-shaped flower is a magenta-pink with scarlet-puple veins, sometimes broad or blotchy. It grows to about 30 centimetres high and wide.
G. maculatum has a clumping form and grows to about 50 centimetres with a width of about 40. Though it has a relatively brief blooming season by Geranium norms, the breathtakingly lovely flowers make up for it. The salver-shaped blooms have a white centre and are a pale, baby pink shade on which the yellow anthers deliver a striking contrast. It is native to the United States and several wonderful cultivars have been developed from it, for example G. maculatum ‘Elizabeth Ann’, an RHS Award of Garden Merit recipient.
G. ‘Melinda’ also has a clumping form and with the same height and width as G. Maculatum. It blooms in summer and autumn. Its purple venation is so unusually prominent and patterned on the pinkish-white petals that it lends the flower a classical delicacy and fragility, bringing to mind Victorian Era porcelain showpieces.
G. x Cantabrigiense ‘Karmina’ makes do with full sun to full shade, has a prolonged blooming season, and has a mat-forming habit, growing to only 15 to 20 centimetres. As such it is a top choice for groundcover, especially as the disk-shaped flowers of a solid bright lilac-pink hue are both acutely pretty and fragrant.
G. cinereum is another mat-forming variety with a height similar to G. x Cantabrigiense ‘Karmina’ and nearly matching its long blooming season, making it too a top choice for groundcover and rock gardens. But flower-wise it is similar to G. ‘Melinda’ as its blooms too are very fragile and refined. The petals’ distal ends have a deep notch and on their pinkish-white base runs a delicate network of purple veins. As with G. maculatum – to repeat ourselves – several wonderful cultivars have been developed from it, for example G. cinereum ‘Ballerina’, an RHS Award of Garden Merit recipient.
G. ‘Danny Boy’ exhibits an extraordinary spreading habit that is open and not dense. Though it is a respectable 50 centimetres high, it spreads to 1.5 metres and may span even 2 metres. It blooms throughout summer, putting on a colour spectacle with its vivid and vibrant purple flowers whose venation comprises of mere streaks in a shifted tone of purple. RHS Award of Garden Merit
We close with G. arboreum or Hawaii Red Cranesbill, an endangered species that has an official status of ‘Critically Imperilled’ and, sadly, is on the road to extinction, at least in the wild. It grows only in a few gulches in Maui. At 2 to 3.7 metres in height it is a giant among Geraniums. The flower is even more unusual; it is of a brilliant magenta-red hue with curled and furled petals, the only ones to exhibit this trait among Geraniums.
Other varieties that are well worth looking into include G. Himalayense, G. Dreamland = ‘Bremdream’, G. clarkei ‘Kashmir White’, G. ‘Orion’, G. ‘Mavis Simpson’, G. ‘Ann Folkard’, G. nodosum ‘Julie’s Velvet’, and G. pratense ‘Mrs. Kendall Clark’. A few of these are RHS Award of Garden Merit recipients while others are under-rated and unsung, but all feature breathtakingly beautiful flowers.
Habitat and Growing Conditions
Geranium is so varied a genus and its species cover such an abundance of regions and biomes that they are found in every conceivable habitat except the tundra. Some species grow at sea level while others thrive on high mountains. For example, G. robertianum flourishes in coastal areas while G. nodosum does equally well on alpine slopes.
Some species prefer open fields and full sun while others prefer woodland shade though it is safe to say that part sun suits most species very well. These plants make do with any type of soil so long as it is not waterlogged or overly-alkaline. Most species have a preference for moist ground.
As the genus is so varied and as its species inhabit just about every climatic zone and biome, species’ USDA Hardiness Zones vary widely. However, most varieties of interest have a USDA Hardiness Zone of 4 to 8.
In the U.K. the native species are found in meadows, woodlands, littoral regions and even on sand dunes.
Where to Plant Geranium
Considering the considerable range in varieties’ heights and spreads, and the fact that they come in all habits and forms, just where a Geranium variety is best planted strongly depends on its characteristics. Consider that G. ‘Mavis Simpson’ grows to all of 20 centimetres, if even that, and is mat-forming, while G. ‘Orion’ is over five times as tall and with a bushy habit.
Most varieties make for superlative beds, borders, and edges. The few mat-forming varieties are excellent choices for attractive groundcover while clumping varieties provide splashes of colour in rock gardens.
A majority of Geranium varieties are of that intermediate height such that in formal gardens they can be matched with taller plants like rhododendrons to set them off, yet can also be used behind smaller ornamentals like pansies.
This leads us to the point that Geraniums are often presented and positioned as excellent ‘companion plants.’ We disagree with any such summation. In our view, Geraniums are standalone ornamental plants in their own rights, and all the varieties mentioned above are a collective ‘Exhibit A’ that prove our position. Plants of this varied and versatile genus can be displayed in a planter on the patio, in pots on a parapet, in hanging baskets on a pergola, and much more.
Feeding, Care and Growing Tips
Among the most unfussy and undemanding of flowering plants, Geraniums will grow in just about any soil and with next to no care. Though this is a simple statement of fact, it should not be misconstrued to suggest that you may neglect your Geranium. For healthy, long-lived plants that adorn your garden with an abundance of blooms for the longest possible flowering season, here are some simple tips.
Plant Geraniums in any fertile loam mix that contains humus or organic manure. The soil must have very good drainage. The ideal soil pH range for most varieties is from 6.0 to 6.5 – Slightly Acidic.
Though a number of varieties can be propagated in seasons other than spring, all varieties can be propagated in spring, and very reliably at that. Apart from seed, Geraniums are easily and naturally propagated by division. The one thing to be careful of is to keep the root ball just at soil level and not any lower. Many varieties can also be propagated from basal cuttings and stem cuttings. Many a robust variety’s stem cutting can be rooted within a month simply by putting it in a glass of water, after appropriate trimming. Remember to change the water every three days or so.
Keep in mind that it is particularly straightforward to collect Geranium seeds by harvesting the capsules.
To plant seeds, nudge them into the earth and cover with a thin sprinkling of soil. Water well and then continue to water every two days or so, so as to keep the soil moist as the seedling matures, tapering off as the plant grows. If grown outdoors, in most areas of the United Kingdom Geraniums’ water needs will be satisfied by natural rainfall.
A majority of Geraniums prefer full sun to part sun whereas some prefer full shade to part shade. A few very sporting varieties, such as G. phaeum var. phaeum ‘Langthorns Blue’ and G. ‘Melinda,’ will flourish in full sun through full shade! You cannot go wrong if you put any Geranium where it gets full sun until around 1 p.m. and shade or dappled sunlight thereafter. In the United Kingdom, temperature ranges are not a concern for Hardy Geraniums.
Geraniums do not need to be fertilised; in fact, over-fertilising can have undesirable consequences. However, they may be fed once a year in early spring with a 5-10-5 fertiliser or simple organic compost.
Geraniums do not need pruning as such but regular deadheading will encourage continuous flowering. However, you may want some flowers to develop seed capsules for harvesting.
Some varieties tend to get leggy and may even look worn out before the end of the season after a spate of flowering. When this happens simply cut back the plant by about half. This will spur fresh growth and even renewed flowering. The more robust varieties can even be cut down to the ground for the plant to re-grow with a new vigour, and produce new foliage and flowers.
For the most part Geraniums are healthy low-care plants. However, now and again a plant can be attacked by vine weevil, geranium sawfly, or capsid bug.
The diseases that Geraniums have a particular susceptibility to are limited to downy mildew and powdery mildew.
Where to Buy Geranium
First, keep in mind that Geraniums are unusually easy to propagate yourself, and that too in three different ways. Plants can be propagated by division and also by cuttings. Seeds are simple to obtain by harvesting seed capsules.
To add to the ease, Geraniums are among the most widely available of plants. All the established varieties are available at brick-and-mortar garden centres and also from online retailers, with a few varieties sold by dozens of sellers. Both potted plants and seed packets are equally easy to find.
Kersie learnt the basics of gardening as a toddler, courtesy of his grandfather. In his youth he was an active gardener with a preference for flowering plants. He is a professional and vocational writer and his freelance projects have spanned various kinds of writing.