*Phlomis*, Jerusalem sage: planting, cultivation and maintenance

Description and Botany

The phlomis comprises around 110 species of perennial plants, herbaceous or bushy, whose native range extends from the Mediterranean region to Asia. The most commonly cultivated in gardens is the Phlomis fruticosa. In the wild, it is mainly found in the eastern Mediterranean basin (Asia Minor, Turkey, Greece, Cyprus, Syria…), which explains its preference for warm, dry, sunny situations. Phlomis primarily grows in rocky environments and dry short grass meadows. In France, three species can be found in the wild: Phlomis herba-venti, Phlomis lychnitis, and Phlomis fruticosa, the latter having naturalised in some areas.

Phlomis belongs to the Lamiaceae family, which includes plants that are often aromatic and quite drought-resistant, many of which are Mediterranean plants. They share common characteristics, found in the leaves (simple, opposite), stems (four-angled), flowers (two-lipped), or fruit, as well as in their adaptation to drought. This includes sage, lavender, thyme, or mint… and other ornamental plants, such as monardas, nepeta, or caryopteris.

Etymologically, its name comes from the Greek Phlox: flame, as the leaves may have been used as wicks for oil lamps. Another possible etymology is that its name derives from the Greek Phlomos, referring to mullein, in reference to the wooly foliage of this plant, somewhat reminiscent of that of Phlomis. The species name fruticosa means bushy, and comes from the Latin word frutex: bush. In French, phlomis is called Jerusalem Sage, as its foliage resembles that of sage… And it is true that phlomis is very close; these two plants are cousins!

Phlomis purpurea: botanical illustration

Phlomis can be herbaceous or bushy. They form wide clumps with dense foliage, which limits the growth of weeds. They measure almost as much in width as in height. Phlomis reaches between 60 cm and 1.50 m tall. The Phlomis italica is among the shortest, often measuring less than 60 cm. The stems of Phlomis are characterised by being square, with four angles. They are long and straight, standing vertically. The Phlomis tuberosa bears very beautiful dark red to purple stems, which contrast nicely with the foliage and flowering.

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

The stems are rhythmically adorned with whorls of flowers, arranged regularly, in tiers. They consist of flowers placed all at the same level, surrounding the stem quite densely. This tiered flowering creates a superb visual effect! This is precisely what gives a very graphic aspect to the flowering of the Phlomis tuberosa ‘Amazone’. Each whorl of flowers is like placed on two opposite leaves (bracts), which adds even more graphic quality to the inflorescence. Moreover, with its long, upright flower spikes, the flowering of Phlomis is well-suited for bouquet arrangements!

The flowers of phlomis often measure two to three centimetres long. The petals are fused into a tube but open into two lips. The upper lip forms a galea, while the lower is divided into three lobes. This corolla (set of petals) is inserted into a calyx (sepals) with five teeth. The flower also has four stamens (two long and two short).

The flowering of phlomis is quite bright! The most well-known is the Phlomis fruticosa, with beautiful bright yellow flowers, while the flowering of Phlomis russeliana is a slightly softer yellow. There are also varieties with pink, mauve, purple, or white flowers!

The flowering of phlomis is appreciated by pollinating insects, particularly bumblebees and carpenter bees.

The flowering of phlomis! In order, Phlomis fruticosa (photo Stan Shebs), Phlomis tuberosa (photo C.T. Johansson) and Phlomis russeliana

Phlomis has rather dense and thick foliage. Its leaves are simple (undivided), oval, and quite elongated. They are wrinkled and generally hairy, pubescent. On the stems, the leaves are arranged in pairs; and each pair is placed at right angles to the previous one (decussate opposite leaves). The leaves of Phlomis fruticosa resemble those of sage, which gives the plant its name of Jerusalem Sage. In Phlomis russeliana, the leaves are triangular or cordate (heart-shaped), broad at the base and tapering towards the tip. The leaves of Phlomis generally measure between 5 and 20 cm long. However, Phlomis lanata is distinguished by its small, relatively rounded leaves, which measure no more than 3 cm in length!

The leaves can be a beautiful light green, but they also frequently take on greyish hues, sometimes slightly bluish. They are generally a bit greyer and wooly on the underside.

In most varieties, the leaves have the advantage of being evergreen! Thus, phlomis remains decorative even in winter. However, Phlomis tuberosa has deciduous leaves.

The often grey and pubescent leaves of phlomis indicate an adaptation to drought, as this reduces evapotranspiration and allows the plant to retain the water present in its cells.

The foliage of Phlomis fruticosa, Phlomis lanata, and Phlomis russeliana

The fruit of phlomis consists of four achenes (tetrachenes), one of the characteristics of the Lamiaceae family. It is contained within the calyx that remains in place after flowering. When the flower spikes have faded and bear fruit, they retain a decorative, very graphic appearance! You can leave them in place for winter, as they will provide structure in the flower beds, as well as an original and attractive aspect, valuable at this time of year.

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

Phlomis is therefore decorative in the garden for almost the entire year, through its summer flowering, its fruits in autumn and winter, as well as its foliage (often evergreen) that resembles that of sage!

The main varieties of Phlomis

The most popular varieties

Our favourite varieties

Phlomis fruticosa - Jerusalem Sage

Jerusalem Sage bears whorls of golden yellow flowers. It also has beautiful greyish, downy leaves, resembling those 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 been awarded the Award of Garden Merit by the Royal Horticulture Society (RHS).

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

See the product sheet

 

Phlomis tuberosa Amazone

This is a fairly tall variety, with slender dark purple stems bearing flowers of a soft and delicate pink, leaning towards mauve. A very graphic 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 offers floral stems in summer bearing flowers gathered in large, fairly dense whorls. These have a beautiful, bright and soft mauve hue.

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

See the product sheet

Phlomis samia

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

• 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 for Mediterranean gardens and sunny rockeries, and it is also well-suited for seaside gardens. Don’t hesitate to place it at the foot of a south-facing wall! However, as a general rule, it can tolerate a slightly shaded position as long as there is enough light.

Phlomis is not very sensitive to soil type. It tolerates poor, even stony soils, and can withstand calcareous terrains. The most important thing is that the soil is well-drained, as this plant is sensitive to excess moisture! If your soil retains water, plant on a mound. Elevating 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, and poor substrate.

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

Phlomis can certainly be placed in a rockery. It is also well-suited for perennial borders, at the edge, or in naturalistic beds (especially varieties like Phlomis tuberosa ‘Amazone’!). As phlomis has a fairly 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 in a region with a mild climate, and spring if you live in a harsher climate.

How to plant?

As phlomis forms fairly large clumps, maintain a good planting distance (70 to 80 cm at minimum).

To plant a phlomis:

1. Place the plant in a basin filled with water to thoroughly moisten the root ball.
2. In the meantime, prepare the ground. Dig a planting hole, adding some gravel if necessary to facilitate water infiltration into the soil. You can also create a mound to plant the plant in an elevated position and prevent water from stagnating later.
3. Remove the plant from its pot and place it in the planting hole.
4. Replace the soil all around.
5. Lightly press down with the palm of your hand.
6. Water generously.

Continue to water in the weeks following planting. Phlomis will then be able to do without further watering.

Phlomis herba-venti (photo Luis Nunes Alberto)

Maintenance

Phlomis has the advantage of requiring very little maintenance! You can let it thrive in a part of the garden without intervention. It tolerates drought and high temperatures well, so it can do without watering. Similarly, as it enjoys rather poor soils, it does not need fertiliser.

It is possible to prune the flower spikes in autumn when they have faded, but we suggest keeping them for winter, as they have a decorative and graphic quality. You can then cut them back at the end of winter (March – April), and take the opportunity to remove any leaves damaged by frost. You can also carry out light pruning after flowering to maintain a more compact and dense habit. For Phlomis tuberosa, as it is a deciduous plant, we recommend cleaning the clump at the end of winter by removing the stems and leaves that have dried out.

Although it is not prone to diseases, phlomis is sometimes attacked by leafhoppers, small insects that pierce the plant tissues to extract sap. The leaves then show small discoloured spots. This can also lead to the appearance of sooty mould; however, generally speaking, the damage is not very significant. You can treat it using neem oil or black soap.

Multiplication: sowing, propagation by cuttings, division

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

Sowing

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

1. Take a pot and fill it with special sowing compost. Firm it down lightly.
2. Sow the seeds on the surface.
3. Cover them with a little compost.
4. Water gently.
5. Place the pot at a temperature between 15 and 18 °C.
6. Continue to water regularly to keep the substrate moist until germination.
7. Be patient… The seeds may germinate after two weeks, but they can sometimes take much longer to emerge: up to two months!
8. You can then transplant the young plants into individual pots. Then, plant them in the ground in autumn or the following spring.

Propagation by Cuttings

You can multiply Phlomis by propagation by cuttings at the end of summer (July – August).

1. Take a segment from a healthy, preferably non-flowering stem measuring 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 the leaves from the lower half of the stem, leaving only a few at the tip.
3. Prepare a pot with a mixture of compost and sand, and water it to ensure it is well moistened.
4. Plant the cutting in the substrate.
5. Firm the soil around the stem to eliminate air pockets and ensure good contact between the stem and the substrate.
6. Place your cutting under a cold frame, protected from frost. The location should be bright but without direct sunlight.

It is advisable to place a plastic bottle or plastic bag over the pot to maintain a humid atmosphere (closed cutting propagation). Just remember to ventilate occasionally to prevent diseases or fungi from appearing.

Tuft Division

Tuft division is possible in autumn or spring. It will allow you to rejuvenate the plants and make them more vigorous. You can do this every three years. Carefully dig up a well-established tuft that has been in place for several years. Separate it into several fragments, then replant them in new locations after preparing the soil.

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

Associating Phlomis in the Garden

Phlomis is truly perfect for Mediterranean gardens and dry gardens. Plant it alongside Euphorbia characias, Stachys byzantina, Verbascum, Cistus… Discover the beautiful blue-mauve, very delicate flowers of Catananche caerulea. Also favour aromatic plants, such as lavenders, salvias, helichrysums, and santolines. You will benefit from having a garden that requires almost no maintenance! This type of planting will be particularly suitable for seaside gardens.

As it is drought-resistant and appreciates poor, well-drained, stony soils, phlomis can easily be integrated at the back of a rockery. Place it in front of some lower plants, in cushions or ground covers, such as saxifrages, moss phlox, sedums, or Corsican euphorbias (Euphorbia myrsinites). Optionally, add some Eryngiums, Helianthemums, Armeria maritima, and sand pinks (Dianthus arenarius). Also enjoy the original flowering of Echinops! For a rockery, we recommend choosing the most compact phlomis rather than the larger varieties. Phlomis lanata seems particularly suitable.

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

For a more classic yet still very colourful and lively planting, you can integrate phlomis into a mixed border. Plant it with hardy geraniums, Centranthus ruber, alchemillas, salvias, and nepeta. It can be installed along a path to bring a lively and bright touch along a passage or walkway.

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

→ Discover more beautiful ideas for pairing Jerusalem sage or Phlomis in our advice sheet!

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