<em>Phlomis</em>, Jerusalem sage: planting, cultivation and care

Description and botany

Phlomis include about 110 species of perennial plants, herbaceous or shrubby, native from Mediterranean region to Asia. Most commonly grown in gardens is Phlomis fruticosa. In the wild this species is mainly found east of the Mediterranean basin (Asia Minor, Turkey, Greece, Cyprus, Syria…), which explains its preference for warm, dry, sunny sites. Phlomis grow mainly on rocky ground and in dry short grass meadow. In France three species occur naturally: Phlomis herba-venti, Phlomis lychnitis and Phlomis fruticosa, the latter becoming naturalised in places.

Phlomis belongs to family Lamiaceae, which groups plants often aromatic and fairly drought-tolerant, many of them Mediterranean. They share common characteristics found in leaves (simple, opposite), stems (four-angled), flowers (two-lipped), fruit, and adaptation to drought. Examples include sage, lavender, thyme or mint… and ornamental plants such as monardas, nepeta or caryopteris.

Etymologically the name comes from Greek Phlox: flame, because leaves were used as wicks for oil lamps. Another possible origin is Greek Phlomos, referring to mulleins, alluding to wooly foliage similar to some Phlomis. Specific epithet fruticosa means shrubby, from Latin frutex: bush. In French Phlomis is called Sauge de Jérusalem because foliage resembles sage… and indeed Phlomis and sage are close relatives.

Phlomis purpurea: botanical illustration

Phlomis can be herbaceous or shrubby. They form wide clumps with dense foliage, limiting weed growth. They are almost as wide as tall. Phlomis reach between 60 cm and 1.50 m. Phlomis italica is among the shortest, often under 60 cm. Phlomis stems are characteristically square, four-angled. They are long and upright. Phlomis tuberosa bears very handsome stems in deep purplish-red, providing a striking contrast with foliage and flowers.

Flowering occurs in summer, often around June and July; but depending on variety it can extend from May to August–September.

Stems are marked by whorls of flowers, arranged regularly in tiers. These whorls consist of flowers all at the same level, densely surrounding the stem. This layered flowering creates a superb visual effect! It is precisely what gives a graphic aspect to flowering of Phlomis tuberosa ‘Amazone’. Each whorl of flowers sits above two opposite leaves (bracts), which adds to the inflorescence’s graphic quality. With long, upright flowering stems, Phlomis are also well suited to cut-flower arrangements!

Phlomis flowers often measure two to three centimetres long. Petals are fused into a tube, opening into two lips. Upper lip forms a galea, lower lip is divided into three lobes. This corolla is inserted into a five-toothed calyx. Flower also has four stamens (two long and two short).

Phlomis flowering is notably bright! Best known is Phlomis fruticosa, with vivid yellow flowers, while Phlomis russeliana has slightly softer yellow. There are also varieties with pink, mauve, purple or white flowers!

Phlomis flowering is appreciated by pollinating insects, especially bumblebees and carpenter bees.

Phlomis flowering! From left to right: Phlomis fruticosa (photo Stan Shebs), Phlomis tuberosa (photo C.T. Johansson) and Phlomis russeliana

Phlomis have dense, fairly thick foliage. Leaves are simple in shape, ovate and fairly elongated. They are puckered and generally hairy, pubescent. On stems leaves are arranged in pairs; each pair is set at right angles to previous one (opposite decussate leaves). Leaves of Phlomis fruticosa resemble those of sage, hence common name Jerusalem Sage. In Phlomis russeliana leaves are triangular or cordate (heart-shaped), broad at base and tapered at tip. Phlomis leaves generally measure between 5 and 20 cm long. Phlomis lanata stands out with small, rather rounded leaves no more than 3 cm long!

Leaves can be a bright light green, but often take grey tones, sometimes slightly bluish. Underside is usually greyer and wooly.

In most varieties leaves are evergreen! Phlomis therefore remain decorative even in winter. However, Phlomis tuberosa has deciduous leaves.

Grey, pubescent leaves of phlomis reflect adaptation to drought, reducing evapotranspiration and helping plant conserve water in its cells.

Foliage of Phlomis fruticosa, Phlomis lanata and Phlomis russeliana

Phlomis fruit consists of four achenes (tetrakene), one of family Lamiaceae’s characteristics. Fruit is enclosed in calyx which remains after flowering. When flower stems have faded and bear fruit they retain a decorative, very graphic appearance! You can leave them in place over winter, as they provide structure in borders and an original, attractive feature at this time of year.

Infructescences of Phlomis fruticosa, those of Phlomis russeliana (photo Dominicus Johannes Bergsma), and seeds of Phlomis tuberosa (photo Stefan lefnaer)

Phlomis are therefore decorative in garden for much of year, by summer flowering, fruits in autumn and winter, and foliage (often evergreen) green-grey, reminiscent of sage.

Main varieties of Phlomis

Most popular varieties

Our favourite varieties

Phlomis fruticosa - Jerusalem Sage

Jerusalem sage bears whorls of golden-yellow flowers. It also has attractive greyish, downy foliage resembling that of true sage!

• Flowering time June to August
• Height at maturity 1,25 m

See the product sheet

Phlomis russeliana - Jerusalem Sage

This Phlomis offers a softer yellow flowering than Phlomis fruticosa, along with large green leaves. It has received the RHS Award of Garden Merit.

• Flowering time July, August
• Height at maturity 80 cm

See the product sheet

 

Phlomis tuberosa Amazone

This is a fairly tall variety, with very slender, dark purple stems bearing flowers of a soft, delicate pink tending towards mauve. A very architectural plant with airy flowering! Its foliage is deciduous.

• Flowering time June to August
• Height at maturity 1,20 m

See the product sheet

Phlomis cashmeriana

This Phlomis produces flowering stems in summer bearing flowers gathered in large, fairly dense whorls. These display a lovely luminous, soft mauve shade.

• Flowering time June to August
• Height at maturity 70 cm

See the product sheet

Phlomis samia

Phlomis samia has a very soft, pale pink, slightly beige flowering. Its leaves are green on the upper surface, grey and downy beneath.

• Flowering time August, September
• Height at maturity 1 m

See the product sheet

Planting Phlomis

Where to plant?

Phlomis is a full-sun plant. It is ideal in Mediterranean gardens and sunny rockeries, and is well suited to coastal gardens. Don’t hesitate to place it at the base of a south-facing wall! However, as a rule, it can tolerate light shade provided there is sufficient light.

Phlomis is not very particular about soil type. It does well in poor, even stony soils, and tolerates calcareous ground. The most important thing is that the soil is well drained, because this plant dislikes excess moisture! If your soil holds water, plant on a mound. Raising the bed will allow water to drain away more quickly. You can also add gravel to improve water infiltration. Ideally, plant in a sandy, light, poor substrate.

As Phlomis has quite a wide, spreading habit, leave some space around it, avoiding planting it too close to other plants.

Phlomis can easily be used in a rockery. It is also suitable in perennial beds, as an edging plant, or in naturalistic beds (notably varieties such as Phlomis tuberosa ‘Amazone’!). As Phlomis has quite a wide, spreading habit, leave some space around it, avoiding planting it too close to other plants.

When to plant?

You can plant Phlomis in autumn or spring. Opt for autumn if you are located in a mild climate, and for spring if you live in a harsher climate.

How to plant?

As Phlomis forms fairly large clumps, respect a good planting distance (70 to 80 cm minimum).

To plant a Phlomis:

1. Place the plant in a basin filled with water to thoroughly moisten the rootball.
2. Meanwhile, prepare the ground. Dig a planting hole, add a little gravel if necessary to help water infiltrate the soil. You can also create a mound to plant on, elevating the plant to prevent water from stagnating later.
3. Remove the plant from its pot and place it in the planting hole.
4. Backfill the soil around it.
5. Press lightly with the flat of your hand.
6. Water generously.

Continue to water in the weeks following planting. Phlomis will then manage without additional watering.

Phlomis herba-venti (photo Luis Nunes Alberto)

Care

Phlomis has the advantage of not really needing much care! You can leave it to thrive in a part of the garden without intervening. It tolerates drought and high heat well, and can therefore do without watering. Similarly, as it thrives in fairly poor soils, it does not need fertiliser.

It is possible to prune the flower spikes in autumn when they are spent, but we suggest keeping them over winter because they have a decorative, architectural appeal. You can then cut them in late winter (March–April), and take the opportunity to remove leaves damaged by frost. You can also do a light pruning after flowering to keep a more compact, dense habit. For Phlomis tuberosa, as it is a deciduous plant, we recommend tidying the clump in late winter by removing stems and leaves that have dried out.

Although not prone to disease, phlomis is sometimes attacked by leafhoppers, small insects that pierce plant tissues to suck sap. Leaves then show small discoloured spots. This can also lead to sooty mould, but generally damage is minor. Treat with neem oil or black soap.

Propagation: sowing, propagation by cuttings, division

Phlomis can be multiplied by sowing, propagation by cuttings or division. We recommend propagation by cuttings.

Sowing

You can harvest in autumn the Phlomis seeds contained in the fruits on faded flower spikes, then sow them in early spring.

1. Take a pot and fill it with seed compost. Firm lightly.
2. Sow seeds on surface.
3. Cover them with a little seed compost.
4. Water with a fine spray.
5. Place pot at a temperature of 15–18 °C.
6. Keep watering regularly so substrate remains moist until germination.
7. Be patient… Seeds may germinate after two weeks, but sometimes take much longer to appear: up to two months!
8. You can then transplant young shoots into individual pots, then plant out in ground in autumn or the following spring.

Propagation by cuttings

You can multiply Phlomis by propagation by cuttings in late summer (July–August).

1. Take a cutting from a preferably unflowered, healthy stem. It should measure between 10 and 15 cm. Cut cleanly with a disinfected knife, just below a node. If there are flowers or flower buds, remove them.
2. Remove leaves on lower half of stem, leaving only a few at tip.
3. Prepare a pot with a mix of potting compost and sand, and water until it is well moist.
4. Plant the cutting in the substrate.
5. Firm substrate well around stem to remove air pockets and ensure good contact between stem and substrate.
6. Place your cutting under a cold frame, sheltered from frost. Location should be bright but out of direct sunlight.

It is best to place a plastic bottle or a plastic bag over the pot to maintain a humid atmosphere (cuttings under cover). Just remember to ventilate from time to time to prevent disease or fungal growth.

Division of clumps

Division of clumps is possible in autumn or spring. It will allow you to regenerate young plants and make them more vigorous. You can do this every three years. Carefully lift a well-established clump, large enough, that has been in place for several years. Divide it into several pieces, then replant them in new locations after preparing the soil.

→ Learn more in our tutorial How to propagate Phlomis or Jerusalem sage?

Pairing Phlomis in the garden

Phlomis is ideal in Mediterranean and dry gardens. Plant it with Euphorbia characias, Stachys byzantina, Verbascum, Cistus… Discover delicate blue–mauve flowers of Catananche caerulea. Also favour aromatic plants such as lavender, sages, helichrysum and santolina. You will enjoy a garden that requires almost no maintenance! This type of planting is particularly suited to seaside gardens.

As it is drought-tolerant and likes poor, well-drained, stony soils, Phlomis can easily be included at the back of a rockery. Place it in front of some lower cushion-forming or mat-forming plants such as saxifrages, moss phlox, sedums or Corsican spurge (Euphorbia myrsinites). Optionally add some Eryngium, Helianthemum, Armeria maritima and sand pinks (Dianthus arenarius). Also enjoy the distinctive flowering of Echinops! For a rockery, we recommend choosing the most compact phlomis rather than large varieties. Phlomis lanata seems particularly well suited.

Phlomis can be integrated into a Mediterranean-style or dry garden. Phlomis fruticosa, Stachys byzantina (photo Plenuska), lavender and Cistus monspeliensis (photo Jean-Pol Grandmont)

For a more classic but very colourful and lively border, you can include phlomis in a mixed border. Plant it with hardy geraniums, Centranthus ruber, alchemillas, sages and nepeta. It can be placed on the edge of a path to bring a lively, bright aspect along a passage or an avenue.

With its long erect, airy and delicate stems, Phlomis tuberosa ‘Amazone’ will fit better into a naturalistic garden. Plant it with tall ornamental grasses (Calamagrostis, Stipa gigantea…), which will catch the sun’s rays beautifully. Add Echinacea purpurea, Cirsium japonicum, as well as teasels (Dipsacus). Fall for the long flower spikes of Veronicastrum! As the variety Phlomis tuberosa ‘Amazone’ has a fairly graphic form, it can also be used to provide contrast in a more modern garden, alongside lower, more compact plants.

→ Discover more great ideas for combining Jerusalem sage or Phlomis in our advice sheet!

For a naturalistic garden: Phlomis samia, Dipsacus fullonum (photo Radio Tonreg), and Echinacea purpurea ‘The King’