Jerusalem sage is a lovely semi-perennial, drought-tolerant addition that adds splashes of bright yellow flowers to gardens. Growing Jerusalem sage for herb or flower is relatively easy, too, with the plant needing little care once it is established.
I. Appearance and Characteristics
Phlomis fruticosa, the Jerusalem sage, is a species of flowering plant in the family Lamiaceae, native to Albania, Cyprus, Greece, Italy, Turkey, and countries of the former Yugoslavia.
It is a small evergreen shrub, up to 1 m (3 ft) tall by 1.5 m (5 ft) wide. The sage-like, aromatic leaves are oval, 5–10 cm (2-4ins) long, wrinkled, grey-green with white undersides, and covered with fine hairs. Deep yellow, tubular flowers, 3 cm in length, grow in whorls of 20 in short spikes in summer.
The specific epithet fruticosa means “shrubby”.
It is popular as an ornamental plant, and has gained the Royal Horticultural Society’s Award of Garden Merit.
As a garden escape, it has naturalised in parts of South West England.
It is listed as deer resistant, hardy in zones 7 to 11, and tolerant of a range of soil types.
II. How to Grow and Care
Sun and Temperature
Phlomis fruticosa grows best in full sun but tolerates some light shade if full sun is inaccessible. 6 to 8 hours of full sun is best in most cases. However, in hotter regions, provide some light shade in the hard afternoon light. In cooler regions, anything less than full sun can produce leggy growth and stunt the plant through the growing season.
Jerusalem sage is hardy in USDA zones 8 through 10, but the plant remains semi-perennial in zones 5 through 7. In the arctic cold of zones 3 and 4, the plant may have trouble returning annually. It is winter hardy down to 23° Fahrenheit and tolerates high heat conditions, especially with a bit of shade to offset warmth. It takes on damage in extremes, however, with resulting affectation occurring on the grayish-green leaves in intense cold and intense full sun in extreme heat.
If you live near zone 10 or somewhere prone to heatwaves, provide light shade by planting it in a dappled sun area or moving taller plants nearby. In the cold, allow the foliage to die back in winter and provide a thick layer of mulch to keep the roots safe until blooms return in late spring.
Water and Humidity
While regular watering is necessary for Jerusalem sage plants shortly after transplanting, these drought-tolerant shrubs won’t need much afterward. As a baseline, about 1 inch of water per week is good, especially for those planted in full sun. During temperate seasons, it won’t be necessary to water beyond a couple of times a week.
Increase watering in early summer and late summer, and cut back in winter. Since Jerusalem sage is sensitive to cold, water slowly and deeply ahead of a freeze to about 3 to 4 inches below the soil line. Use either drip irrigation or soaker hoses. Careful hand watering is fine, too, as long as it is slow and focused at the base of the plant rather than its leaves.
Water in the morning or at dusk. Morning is preferable, as this will give the roots of Jerusalem sage plants time to absorb the water as the soil warms. The plant adapts to varying levels of humidity, ranging from fully drought-tolerant to the humidity of the Mediterranean coast.
Soil
Your Jerusalem sage needs semi-fertile, well-draining soil. You can amend the soil when you transplant in late spring or fall by adding a little bit of well-rotted compost to the planting site. If the native soil is compacted, aerate it and provide some agricultural sand or perlite to promote drainage. Once established, your plant will thrive in most soil types, provided they drain well. Phlomis fruticosa especially loves gravel as a growing medium. It has a wide pH tolerance, from mildly acidic to slightly alkaline.
Fertilizing
Jerusalem sage plants don’t need fertilizer to thrive, but annually in fall, you can add well-rotted, fertile compost to the base of the plant on the soil’s surface to assist with nutrient replenishment. Compost contains basic and trace nutrients needed to support further growth in early spring.
Planting Instructions
Plant Jerusalem sage in the spring. Dig a hole at least twice the size of the nursery pot and just as deep. Place the plant in the hole and backfill with the original soil so that the top of the root ball is flush with the soil. Tamp down the soil and water it well. Keep the soil moist for the first few weeks and water it regularly during the first growing season to encourage a strong root system.
Space plants 3 to 4 feet apart.
Pruning
Jerusalem sage loves heavy pruning in fall. This allows for more vigorous growth in its late spring season. If you do not want the plant to spread and sprout in late spring due to explosions of attractive seed heads in winter, deadhead them as the blooms fade. Alternatively, you can cut them while they are in bloom and put them in floral arrangements to promote a second flower period.
Winter pruning, especially in colder regions outside the plant’s hardiness zone range, is very important. Cut the woody stalks of the plant to the ground with a sanitized pair of pruning shears. Then add a layer of mulch to its base to protect the roots. In USDA zones 8 to 10, mulch may not be necessary.
Propagation
There are three ways to propagate Jerusalem sage: dividing the root ball in the spring, rooting softwood cuttings in the summer, or sowing seeds in late spring.
The seeds can be direct sown outdoors after the last danger of frost but in areas with long winters, it is best to start the seeds indoors in pots or cell packs. Press 3 to 4 seeds into the soil and cover it only with a dusting of soil. Keep the soil evenly moist. At a temperature around 65 degrees F. germination takes 40 to 60 days. Thin to the strongest seedling in each pot. Transplant the seedlings outdoors after the last spring frost.
Potting and Repotting
Jerusalem sage is suitable to be grown in containers. Use a pot at least 5 inches wider in diameter than the nursery pot and make sure it has large drainage holes. Fill the container with a well-draining potting mix. Keep in mind that container plants need more frequent watering and fertilizer than inground plants.
Although the plant is winter-hardy, growing it in a pot exposes its roots to frost and freeze-and-thaw cycles. The pots should remain outdoors during the winter but you need to protect the roots by burying the pot in the ground or insulating the roots by placing the pot in a second, larger pot to create a planting silo.
When grown as an annual, Jerusalem sage won’t require repotting during its single growing season. Otherwise, repotting to a larger container with fresh potting mix will be required when the roots outgrow the pot.
Pests and Diseases
Growing Problems
You may have an issue with an overwhelming amount of Phlomis depending on how many plants you have grown. If you’re like me and know you tend to overplant your gardens, take a look at a plant calculator before you begin gardening with this Turkey native.
Monitor those Phlomis species planted in shade. They may get leggy and lack flower petals as the tips extend and search for light. You may experience a ton of spread if you don’t clip back the blooms in autumn. It’s fine to leave the seed for native wildlife to consume in cooler months. Note that you may need to pull up newly planted seeds from each germinated dried flower head in spring if you provide habitat.
Pests
This deer-resistant plant also wards off most species of disadvantageous insects as well. The only insect that can be a problem is the leafhopper, which can spread diseases to the leaves and flower stems of your plant as they hop around.
If you search and find them, spray the sage planted in your garden with water. Keep the area around your plant clean, and dust this evergreen with diatomaceous earth or kaolin clay to keep them away. Keep these off and away from the flower heads to avoid harming pollinators.
Diseases
There are very few to no diseases to worry about when gardening Phlomis evergreen plants. They are incredibly resistant to oak root fungus, which tends to crop up in years when there are heat-filled early summer and moist winter months.
However, overwatered plants can experience root rot in warmer USDA zones in early summer. Make sure your sage garden receives enough water in the hot summer to help your plants flower, but not so much that it stands in water constantly. Similarly, plants in shade may be more susceptible.
The rule of thumb here is to ensure the top 3 to 4 inches of garden soil are dry before watering occurs again. This will keep your sage evergreen and promote the attraction of butterflies and other pollinators to the bright yellow flowers.
III. Uses and Benefits
- Ornamental uses
Shrubby jerusalem sage is a popular semi-evergreen shrub prized for its bright yellow flowers and green foliage. It is commonly used as a hedge or ornamental garden plant and is essential in Mediterranean gardens. Plant it with salvias, agave, olives, rosemary, Santolina, and rosemary for contrasting color and texture.
- Culinary uses
Jerusalem sage leaves go well in soups and stews or mixed into butter and bread for a lovely flavor akin to culinary sage.
- Other uses
The leaves on the upper half of the plant were used as lamp wicks by ancient peoples.
IV. Types of Jerusalem Sage
Tuberous Jerusalem Sage
Tuberous Jerusalem sage (Phlomis tuberosa) has tubular, lavender-pink flowers that grow in dense, whorled clusters between May and July. It reaches 2 to 4 feet in height and spreads 1.5 to 2 feet. The plant is native to central and southeastern Europe and Asia. Zone 6-9
Turkish Sage
Phlomis russeliana is native to Turkey and Syria where it grows in open woodlands and clearings. It has large, roughly-textured, olive-green, aromatic leaves and pale yellow flowers between June and September. Its mature height is 2 to 3 feet and its width is 1.5 to 2 feet. Zone 5-9
Purple Phlomis
Growing 4 to 6 feet tall and almost as wide, purple phlomis (Phlomis purpurea) is more of a sprawling shrub. It is native to Spain and North Africa. In late spring to summer, rosy-lavender hooded flowers appear in whorls just above the woolly, gray-green foliage. Zone 9-10.
Find Where to Buy the Best Jerusalem Sage (Phlomis fruticosa)
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