How To Grow Geraniums
The hardy Geranium is a genus of over 300 species from temperate regions of both hemispheres. They are invaluable for their pretty flowers, attractive foliage, and their ability to cover the ground, a contribution in the suppression of weeds in the border.
They have a willingness to flourish without any special attention, and what is more they are disease-resistant which in my book makes them irreplaceable for most garden situations. They get their common name of "Cranesbills" from the shape of the seed heads after the petals have fallen. They are long-lived and easily propagated, so from the purchase of just one plant; by division it is possible to quickly increase the stock.
Some confusion exists between geraniums and pelargoniums also frequently referred to as geraniums. The mix-up can be traced back to the eighteenth century and though both are members of the same plant family, they are very different. The pelargoniums or 'Annual Geraniums'; are in fact very unlike the hardy "Cranesbill" for they are only half-hardy being frost tender plants with a single flower stem holding a flower head made up of florets. It was Joannis Borman, 1738/1739 who first proposed pelargoniums as a group separate from Geraniums. Unlike the half-hardy Pelargoniums, Cranesbill flowers come in shades that also occupy the blue-end of the spectrum spreading towards pinks but do not produce any of the deep vivid reds as the Pelargoniums. Many begin to flower in late spring/early summer and continue on until autumn.
Leaves of hardy geraniums are typically divided into leaflets arranged in a palm-like fashion. They range from the thumbnail-sized brown leaves of G. sessiliflorum 'Nigricans' to the rich mid-green dinner-plate-sized leaves of G. maderense. You can find leaves with all sorts of veining, and blotching of white to deepest maroon and purple. Even when not in flower, the intricately cut foliage makes a handsome addition to the borders giving valuable texture and interest, mixing well with other herbaceous plants.
Many are herbaceous perennials that die down in winter and flower again year after year. They vary in growth from about 6" (15cm) to 4ft (120cm) tall depending on variety. New and lovelier varieties appear on the market each year and few gardens are complete without at least one of them.
Geraniums grow well in well-drained soil in sun or shade, depending on the species. Their position in the border will also depend on the growing height, for some are low growing and can be placed at the front of the border while others are better placed to the centre where they will be at their best. Some less vigorous species are useful in rock gardens (e.g., Geranium cinereum 'Lawrence Flatman').
Geraniums require well-drained, fertile, soil. All are low-allergen plants, and most are drought tolerant. However they should not be allowed to dry out; in very dry summers make sure that the plants are frequently watered. If you garden in an area with hot, sunny conditions then most of the species will benefit from a position where there is some dappled shade in the hottest part of the day. However some do better in permanent shade such as G. Nodosum while G. Phaeum requires deep shade. Cutting back old flowering stems keeps the plant tidy and often encourages a further flush of flowers.
Most hardy geraniums are easily propagated by division, which can be done either spring or autumn. Root cuttings may also be used and should be taken after flowering has finished. Many species are also easy to grow from seed and many will come true as long as there are no other compatible species in the garden. In most cases seed pods split from bottom to top into five sections and the seeds are then shot some distance away or simply fall to the ground, depending upon the species. G. Robertianum self-seed easily and spread quickly, therefore wonderful grown in a wild garden situation.
Seed is collected when it is ripe which is easy to detect as the seedpod undergoes a colour change from green to brown. This is a sign of ripeness but there will be varying degrees of colour depending upon the species. Luckily most species flower and set seed over a long period of time so there can be plenty of opportunity in which to collect it. However germination of Geranium seeds can be quite erratic, often taking a long time for seedlings to appear. Seeds may be sown from early February to late June in good free draining seed compost just covering the seed with compost or vermiculite. Make sure the compost is moist but not wet. If you are planting into pots, push a couple of sticks (lollypop sticks are ideal) into each pot and cover with a polythene bag.
If you are sowing into trays you can rig something similar to keep the polythene from touching the seedlings. Maintain a temperature of 13-20C (55-68F). Germination takes 21-60 days. The germination period will depend very much on the variety being sown as will the temperature; some germinate better at a slightly higher temperature. Even the sowing time may differ with variety; some can be sown again in September to October. If you are starting your collection by seed, details of propagation for each variety will be contained on the seed packet.
DOUBLE FLOWERING GERANIUMS:
G. himalayense 'Plenum' Double, purplish-pink flowers flushed-blue with darker veins with fern-like, mid green leaves. This lovely pink Crane's Bill makes an excellent, long-flowering groundcover plant for a cottage garden or herbaceous border. After the main flush in early summer, it flowers intermittently until early autumn. Copes well with full shade. H. 10in. (2.5cm).
GERANIUMS FOR ROCK GARDENS:
G. cinereum 'Ballerina' Deep pink summer flowers with dark-maroon veins and centres and deeply lobed, grey-green leaves. This dwarf form of hardy geranium is particularly suitable for a rock garden. As long as it is given good drainage it will produce a mass of attractively veined pink flowers from late spring to early summer. H. 4in. (10cm).
G. 'Ann Folkard' is a scrambling ground cover, which has saucer shaped, flowers with rich dark centres and veining, flowers all summer long. H. 20in (50cm)
G. psilostemon A.G.M. This vigorous Armenian Cranesbill produces a mass of shallowly-cup shaped, vivid magenta flowers with black centres and veins from early to late summer. It quickly forms loose hummocks of deeply cut, mid green leaves, which turn a fabulous shade of red in autumn. An excellent plant for the middle of the border. H. 4ft. (120cm).
PALE PINK FLOWERS:
G. pratense 'Mrs Kendall Clark' Pearl-grey, saucer-shaped summer flowers, dusted pale pink and finely cut mid-green leaves. This exquisite meadow Crane's Bill is one of the tallest and most vigorous hardy geraniums. It self-seeds freely, although the offspring are likely to vary. An elegant plant for the middle of sunny border. H. 3ft. (90cm).
DEEP PINK FLOWERS:
G. psilostemon 'Fluorescent' Incredible fluorescent, shimmering pink flowers with a jet black eye, create a carpet effect just above the foliage of this impressive perennial. A robust and striking border plant. Flowers: Spring to summer. H. 48in. (120cm). Position: Sun or Part Shade.
G. macrorrhizum 'Bevan's Variety' Clusters of dazzling, crimson-purple, saucer-shaped, summer flowers and aromatic, light green leaves turning orange-yellow in autumn. The deeply cut, scented, semi-evergreen foliage soon spreads to form low hummocks. A reliable plant for a dry, shady spot. H. 20in. (50cm).
BEST BLUE FLOWERS:
G. bohemicum 'Orcid Blue' Clusters of orchid-blue, saucer shaped flowers with purple-violet veins and soft green, leaves. This stunning plant soon spreads to form low hummocks of deeply cut foliage, valuable for suppressing weeds at the front of the border. Although short-lived, new plants are likely to appear year after year, since it self-seeds freely. H. 1ft. (30cm).
G. ibericum 'Johnson's Blue' Flowers growing proud of the leaves, finely cut foliage. This is a particularly lovely variety with elegant blue flowers. A clump forming plant with good ground cover characteristics. H. 2ft. (60cm).
BEST WHITE FLOWERS:
G. renardii Clusters of saucer shaped, white to pale-lavender flowers with bold violet veins in early summer and velvety, rounded, sage-green leaves. This stunning hardy geranium thrives in poor soil. A reliable and tactile foliage plant, however it can be shy to flower. Excellent front of border and groundcover. H. 1ft. (30cm).
G. macrorrhizum This pretty rock Crane's Bill is smothered with clear-white, saucer-shaped flowers from July to October. It soon forms a strongly aromatic carpet of deeply cut, light green leaves, which colour beautifully in autumn. An excellent and reliable groundcover plant in full sun or part shade. H. 20in. (50cm).
BEST PURPLE FLOWERS:
Geranium phaeum Nodding, reflexed petals in shades of deep maroon to almost black. It makes excellent ground cover for a damp shady spot. Flowers: Spring to Summer
H. 2 ft. (60cm).