Four Geraniums for the rock garden

Pretty in pink

There are innumerable hardy geraniums, including many selected cultivars and garden-bred hybrids, suitable for almost any position in the garden. Many make excellent ground cover between shrubs and trees. Others are worthy of a proud position in the hardy perennial border. But there are a few, chiefly species, that are small enough and sufficiently restrained for a place among the alpine elite. I have chosen four Geraniums for the rock garden, all with flowers in various shades of pink, to show what the genus has to offer to the keen alpine gardener. All of them thrive without undue attention in my damp North Wales garden. Happily, none has ever over-reached itself in the search for lebensraum.

Four Geraniums for the rock garden

Geranium sanguineum and var. lancastrense

I give this species pride of place because it is the only British native among the four.

It is also found in similar situations throughout most of Europe, the Caucasus and in Northern Turkey. The common name for the usual form seen is ‘Bloody cranesbill’, self-explanatory as the illustration shows. In Britain it is found in native grassland, rocky places, sand-dunes and open woods on calcareous soils. Geranium sanguineum var. lancastriense (also illustrated) is identical in all respects except for the pure pale pink colour of the flowers. This species is the earliest of the four to flower in our garden, usually starting in April and continuing until mid summer. Once you have it you are unlikely to ever be without it, an easy, very attractive plant.

Geranium dalmaticum

This blooms later, giving a good show from mid-May to July. It is particularly floriferous, even in part shade; a useful attribute. There is also a fairly commonly seen white form ‘Album’, which is a good deal less vigorous in my experience. This geranium has a very limited distribution in the wild, only found in Albania and neighbouring Macedonia and Montenegro.

Geranium cinereum ‘Ballerina’

This geranium has been repeatedly placed in the ‘top ten’ of alpines for the rock garden in occasional surveys of AGS Members. That indicates how indispensable it is, and it’s an easy, long-lived plant. The foliage is greyish-green rather than the strong silver of Geranium argenteum, but lovely nevertheless. The flowers are distinct from other forms of G. cinereum by virtue of their darker eyes and radiating veins.

Geranium cinereum has two distinct centres of population in the wild. In the Balkans it occurs close to but mostly further north than G. dalmaticum. This form is distinct and separated taxonomically as Geranium cinereum subsp. subcaulescens. The Pyrenean form is recognised as Geranium cinereum subsp. cinereum.

The cultivar ‘Ballerina’ arose as a cross between the two subspecies.

Geranium argenteum

‘Argenteum’ means literally the colour of silver coins, whereas ‘cinereum’ means grey, which tells you one of the chief differences between the plants. Geranium argenteum is truly silvery, and on a sunny day in midsummer it glints in the bright sunshine. The flowers are a paler pink than those of the others discussed here, very delicately veined magenta. The combination is truly beautiful and I await the flowering of this special plant with eager anticipation. As mentioned above, it is slower growing than the others, not spreading much but forming a rounded clump. It MUST have the fullest sunshine and most perfect drainage if it is to realise its full potential.

Geranium argenteum ia another species from the Balkan peninsula, but it also occurs quite separately in France and Italy. It is mostly restricted to mountain screes, rock crevices and dry grassland.

Propagation

All geraniums may be propagated from seed, but if only a few plants are required splitting an established clumps is easier and quicker. Only Geranium argenteum, which is slower growing, some would say more refined than the others, would likely resent such butchery. You may move divisions immediately to their permanent homes. Or pot them up in a good fertile but well drained compost until they are well established. Division is best done either in spring before flowering, or in the autumn, but well-watered summer divisions should thrive.

Sow seed from your own plants as soon as it is ripe as it is readily released from the pod and lost. I sow seed from the AGS Seed Distribution or other sources in January along with other alpines. That way they can receive any necessary cold treatment, although most geraniums don’t seem to need it. Use a standard well-drained seed compost, preferably containing loam. Seedlings should be ready to prick out into more of the same by mid-spring. Keep them growing well and you should be able to plant them out either by the autumn or in early spring the following year.

Pests and diseases

Alpine geraniums are generally remarkably free of damage by pests and diseases when grown in full sun in well-drained soil. You may need to take precautions to protect seedlings against molluscs (slugs and snails) in a particularly damp year.

Author: John Good