I am referring to the perennial cranesbill geraniums and not the half hardy pelargoniums commonly bought as bedding plants and usually discarded at the end of the year. There are numerous named species and cultivars: many so similar in appearance, with only subtle distinguishing features, that only a geranium expert could identify them with any certainty. Without labels (which sometimes are the only indication of how pretty their flowers are) and especially when not in flower they are often overlooked in nurseries and garden centres. This is because; although their individual palmate leaves are attractive, the plant as a whole lacks a distinct shape with any flowers ( on young plants especially) often only sparsely spread among the foliage. So why buy them and how are they best used in the garden to maximise their contribution to a planting display even when not in flower and (with larger types) avoid them flopping or growing over and smothering neighbouring plants?
I loosely group them into one of three visually identifiable growth habits: carpeting, clump forming and scrambling. These growth habits do overlap but it helps when trying to decide the best location to plant them and associating them with their most suitable neighbours. Geraniums species in general are best considered as useful supporters of other plants that have strong colour, form and texture. When allowed to weave around plants with strong architectural foliage and/ or colour they can add another dimension to the planting display by harmony or contrast.
Carpeting forms are low growing and many make excellent weed supressing ground cover provided the ground has been thoroughly cleared of weeds prior to planting. They are best used at the front of a border or beneath structural plants with clear stems such as roses, shrubs or trees; where when they themselves are under-planted by bulbs the whole planting association contributes to maximising the length of interest in the planting.
Although several species are semi- evergreen Geranium macrorrhizum and its cultivars are noticeably more so and can provide leaf colour during the winter months. They have aromatic foliage growing to about 15” (40cm) tall; and once established they do spread but not vigorously; any unwanted growth is easily removed as growth is not too deep.
Geranium x cantabrigiense (a cross of G.macrorrhizum and G. dalmaticum) and its cultivars also make excellent tidy ground-cover, their foliage being, like G.macrorrhizum , scented; of little surprise with G. macrorrhizum being one of the parents.
Geranium x antipodeum ( I cannot find reference to them in my books and assume they must be relatively recent introductions. The specific epithet suggests an Australian /NZ breeding) cultivars are also low front of border carpeting forms with small colourful leaves ranging from silvery, bronze or purple. Like all geraniums, once established one does need to keep a cursory eye on to prevent them encroaching other plants but again they are easily controlled. All carpeting forms work well with compact neighbours (which grow no more than 30-40cm) with interesting foliage such as heucheras, tiarellas, bergenias, carex grasses etc.
Finally, to date, I have found G. sanguineum cultivars with their delicate close foliage to make useful ground cover. They are a little slower to establish, often being used in rock gardens but there are a large number of cultivars all with similar foliage appearance but striking differences in flower colour. This makes them particularly useful as accessories to highlight attributes of neighbouring front of border plants.
To avoid this blog becoming too lengthy and tiring to read in one reading I have decided to publish it in two parts with the hope that like any gripping series the reader looks eagerly forward to the next instalment. Titled: Clump forming and scrambling geraniums to enhance planting displays.