Phlomis tuberosa Prima Donna - Sage-leaf mullein

Phlomoides tuberosa ‘Prima Donna’, better known as Phlomis tuberosa ‘Prima Donna’, is a tuberous phlomis with an elegant silhouette and whorls of lilac flowers. Its purple stems bear layered crowns of flowers that punctuate borders in spring or summer. This Jerusalem sage has low, dark green foliage, and sends up its stems above neighbouring perennials. Plant it in a sunny border, a flower meadow or a gravel garden.

This variety belongs to the Lamiaceae family, a cousin of sages, thymes and nepetas. The type species Phlomoides tuberosa grows naturally in Central and Eastern Europe, as far as China; a distribution area that covers the Balkans, Russia, the Caucasus, Central Asia, Mongolia and several Chinese regions. It frequents meadows, clear forest edges, grassy steppes, dry slopes and well-drained soils. Its botanical synonyms are Phlomis tuberosa, Phlomidopsis tuberosa, Phlomitis tuberosa and Trambis tuberosa.

‘Prima Donna’ is a more compact horticultural selection, with dark stems and decorative lilac flowers. It is a deciduous herbaceous perennial: the rootstock lives for several years, the stems die back in winter, and new shoots emerge from the ground in spring. The roots are swollen and tuberous, giving rise to the name tuberosa. The clump slowly thickens from the rootstock. The foliage forms a low cushion of dark green, triangular leaves, rough to the touch, strongly toothed on the edges. Basal leaves are carried on long petioles; those on the stems are smaller. This plant reaches 80cm to 1.20m in height depending on soil fertility. Flowering occurs from June to August: it begins in late spring in mild climates and shifts to July-August in cooler climates. The tubular, pinkish lilac to lavender pink flowers are grouped in superimposed whorls around the stems. Each flower has a hooded upper lip and a more open lower lip. The calyces persist after flowering; they are useful for dried bouquets and remain decorative in the garden in winter. The flowers mainly attract large pollinators capable of visiting the tubular corollas. The hardiness of this variety is excellent, down to around -20 °C, or even more in dry soil.

Group this phlomis with perennials and grasses in slightly wild scenes. Choose, for example, Achillea ‘Credo’ with creamy yellow umbels, Salvia verticillata ‘Purple Rain’ with light violet flowers, Schizachyrium scoparium ‘Blue Heaven’ for its bluish foliage that colours in autumn and Eryngium bourgatii ‘Pico’s Amethyst’. In the garden, keep a few dry stems in winter if you like architectural silhouettes in the frost.