With tuberous Jerusalem sage, a perennial bed can be attractively designed over several levels. Here are details about the mostly unknown plant and tips for care.
Profile of tuberous Jerusalem sage:
Scientific name: Phlomoides tuberosa or Phlomis tuberosa
Plant family: mint family (Lamiaceae)
Other names: sage-leaf mullein
Sowing time: spring
Planting time: spring to autumn
Flowering period: June to July
Soil quality: sandy to loamy, moderately nutritious
These information are for temperate climate!
Use in: flower beds, bouquets, borders, cottage garden, flower garden, natural garden, prairie garden, rock garden
Winter hardiness: hardy, USDA Plant Hardiness Zones: 5 (-26 °C / -15 °F)
Bee and insect friendly: Yes
Plant characteristics and classification of tuberous Jerusalem sage
Plant order, origin and occurrence of tuberous Jerusalem sage
The tuberous Jerusalem sage (Phlomis tuberosa) from the mint family (Lamiaceae) belongs to the little known and underestimated genus of Jerusalem sage (Phlomoides). The exceptionally decorative flowering plant provides structure in the garden and is an ornament in every bed even in winter. Phlomoides tuberosa grows wild on dry slopes, on fallow land, in sunny steppe and meadow landscapes. It is accordingly easy to care for and frugal in the garden. The perennial originally comes from Central and Southeastern Europe and the Caucasus.
Characteristics of tuberous Jerusalem sage
Tuberous Jerusalem sage forms stiff, upright, purple-colored stems that hardly branch. The cluster-forming perennial reaches between 80 and 120 centimeters (32 and 48 in) in height. As the name already suggests, the shoots of the plant grow out of the tubers in the ground. These tubers are said to be edible when cooked.
The leaves of the sage-leaf mullein, as the plant is also called, are rough to the touch and are lanceolate to heart-shaped. Towards the top they become increasingly diminutive. They are arranged opposite and stalked.
The special thing about tuberous Jerusalem sage are its pink to purple violet flower whorls, which are stacked on several levels. They are made up of 14 to 40 simple lip-shaped flowers each. The flowering period lasts from June to July, but the inflorescences last the entire winter and, when covered with snow or hoar frost, make a beautiful picture.
After the bloom, sage-leaf mullein forms small, brown nuts that contain the seeds.
Tuberous Jerusalem sage – cultivation and care
A sunny location in the garden is essential so that the tuberous Jerusalem sage thrives well.
In the garden, sage-leaf mullein prefers a dry, well-drained, sandy-loamy soil with a moderately high nutrient content, as the perennial also finds in its natural habitat.
Maintain a planting distance of 50 centimeters (20 in) when planting the tuberous Jerusalem sage. There are four plants per square meter (10 sq ft).
Sage-leaf mullein is very undemanding. The only measure is pruning close to the ground in spring. Not earlier, otherwise you will deprive yourself of the pleasure of the decorative autumn and winter dress.
The plant is propagated by division or sowing.
The tuberous Jerusalem sage is a very restant perennial that can stay in the bed for decades. Dividing the rootstock is strongly recommended after ten years at the latest. But you can divide it at any time for propagation.
Diseases and pests
The perennial usually does not have any problems with diseases or pests, even snail damage rarely occurs.
The tuberous Jerusalem is hardy down to (-26 °C / -15 °F). If you like you can put some brushwood for winter protection.
Use in the garden
In garden design, Phlomoides tuberosa plays an important role as a structural plant in the perennial bed. With its tiered flowers and its tall growth it forms a decorative center. But it can also be set in the background. Their austere appearance is loosened up by plant partners such as arching overhanging ornamental grasses, lavender or sage. As most members of the mint family, tuberous Jerusalem sage is an important nectar and pollen plant and comes into its own both in the natural garden and in the sunny, dry prairie garden. A beautiful transition can be created on light wooded edges. It also cuts a fine figure as a cut flower.
New cultivations of the plant are usually more intensely colored than the wild species. The most common is the selection ‘Amazone’, which remains at 60 to 80 centimeters (24 to 32 in) a little smaller and blooms in bright pink-violet.