Plant profile: Digitalis
Versatile foxgloves come in many guises and can add lightness, romance or architecture, depending on the scheme
Foxgloves are popular in a host of planting styles from traditional cottage gardens to the contemporary perennial plantings of Piet Oudolf and the New Perennial movement.
There are 25 species and forms in the genus Digitalis, found throughout Europe, northwest Africa and central Asia in a range of habitats from woodland clearings to sub-alpine meadows. The only true biennial is Digitalis purpurea and its cultivars, although some modern purpurea hybrids are classed as short-lived perennials. Most foxgloves, including ancient species and modern hybrids, are perennials, whose lifespan varies according to the growing conditions but is usually three to five years.
Perennial species are divided into two groups: herbaceous perennials, such as D. grandiflora and D. lutea, which die down during cold winters and those retaining an evergreen rosette, including D. parviflora and D. ferruginea. The species flower from early to midsummer but the new hybrids are sterile, so flower for a longer period – from spring to autumn and beyond during mild winters – because they do not set seed. They also tend to swap elegance for robustness, producing denser spikes of more upright flowers.
“People are familiar with the foxglove, so are not overawed by the variety, meaning we can offer many of the more unusual ones and people are prepared to give them a try,” explains Terry Baker, holder of the Digitalis-National Collection.
The natural elegance of all the cultivated species can be used to add lightness, romance or architecture, depending on the scheme. Smaller species, such as D. lutea and long-flowering modern hybrids, including D. purpurea ‘Dalmation Peach’ with its subtle, pale-apricot flowers, are ideal for growing in pots in courtyard gardens. For larger gardens, drifts of white foxgloves, such as D. purpurea ‘Dalmatian White’ or D. purpurea f. albiflora look magnificent
when planted among Betula utilis var. jacquemontii, with ferns; their white flowers described by Terry as looking “ethereal at dusk”.
Among the most popular choices for garden designers are white-flowered forms and selections from the sterile Polkadot Series. These hybrids were developed by Charles Valin, a plant breeder at Thompson & Morgan, and like many new hybrids they produce dense, flower-filled spikes over a long period with individual flowers that are larger than traditional digitalis. Two other sterile hybrids, ‘Lucas’ and ‘Martina’, were bred in the Netherlands by Maarten van der Sar to make short, well-branched plants for containers, although ‘Martina’ at 1m, is tall enough for use in borders.
D. ferruginea, described by the botanist Carl Linnaeus in 1753, is now a stalwart of New Perennial plantings and often used as a counterpoint to grasses such as Stipa tenuissima and Stipa gigantea. Slender in stature with attractive honey-brown flowers densely packed along the stem, it exudes elegance and sophistication in flower and has a strong architectural form in winter, when frosted and festooned with spider webs.
Some of the smaller species such as D. minor and D. obscura are so dainty that they are ideal for screes, or rock gardens. I grow D. laevigata to provide interest among shrubs and myrtle, or to embellish a bulb bed.
In 1785 the English botanist and physician William Withering published An Account of the Foxglove describing its medicinal use in the treatment of ‘dropsy’ as it regulated and strengthened the heartbeat. Digoxin, derived from the leaves of the plant, is still used in some drugs today. It was once prescribed for the treatment of epilepsy, and too much can effect a patient’s vision, creating halos around objects and making the colour yellow seem more prominent. It is thought this was prescribed to Vincent van Gogh during in his ‘yellow’ period – evidenced notably in his painting The Starry Night. And in his Portrait of Dr Gachet he depicts the physician with a stem of D. purpurea. The foxglove has an impact on art whether the medium is oils or plants.