Jerusalem sage: location, toxicity & the most beautiful species
The showy, whorled flowerheads of Jerusalem sage make it an interesting ornamental plant. But even in winter, the plants still have a beautiful decorative effect due to their stable structure.
The Jerusalem sage genus (Phlomis spec.) is composed of just over 120 species, of which only about 4 have been found to be suitable for garden use. In this article you will learn everything about the correct location of Jerusalem sage, whether it is a poisonous plant, and also we will introduce you to the most significant species in more detail.
Contents
Jerusalem sage: Characteristics and origin
Jerusalem sage belongs to the labiates family (Lamiaceae). The origin and distribution areas of the species extend mainly over the Near East, Central Asia and parts of South Asia – isolated variants also have their home in parts of Southern Europe. Natural habitats vary somewhat from species to species, including sunny forest edges, rocky heaths, or drought-resistant grasslands, for example. In the genus are represented perennials, semi-shrubs and shrubs. Thus, the plants are perennial and usually have sufficient winter hardiness.
The growth habit of the species and especially the height of growth differ greatly. Some varieties grow very upright, others more bushy or flat carpet-forming. The intensity of the pubescence of the stem and foliage also depends on the species. The undivided, grey-green to silvery leaves of Jerusalem sage are opposite on the stem and have a full, notched or toothed leaf margin. The hermaphroditic, mirror-symmetrical flowers assemble in so-called false whorls, which are distributed in several tiers on the stem. Flower colours include yellow, white, pink and purple. The flowering time of Jerusalem sage extends largely from May to July. Even late into winter, the unusual structures of the seed heads can be admired in the garden.
Is Jerusalem sage bee friendly? Jerusalem sage is not necessarily one of the most relevant plants for bees, as the nectar and pollen supply of other plants is also still quite high when Jerusalem sage is in bloom.
The most beautiful varieties and species of Jerusalem sage
Below we present the species that have proven to be durable and suitable for the garden. Despite the diversity of species, here are rather few Jerusalem sage varieties.
Turkish sage (Phlomis russeliana)
Turkish sage, also called Syrian Jerusalem sage, is a deciduous, clump-like perennial that forms a rhizome and short stolons. It reaches heights of growth between 60 and 100 cm and is particularly persistent. The hairy foliage of Phlomis russeliana is grey-green and the basal leaves persist on the plant even in winter in mild regions or sheltered locations. The lip flowers of the species are bright yellow. Occasional, brief dry spells can be well tolerated by Turkish sage but it feels most comfortable in more or less permanently fresh soil. It is also worth mentioning that the vigorous species willingly reproduces by self-seeding, so it makes perfect sense to combine it with competitive plants. Turkish sage is hardy down to about -34 °C.
Tuberous Jerusalem sage (Phlomoides tuberosa; syn.: Phlomis tuberosa)
Tuberous Jerusalem sage is also a deciduous, clumpy perennial but it forms root tubers that are edible when cooked. Its height of growth is about 80-130 cm. The upright stems of this species have a wine-red colouration and harmonise well with the pink-purple flowers. The elongated leaves of tuberous Jerusalem sage have a coarsely toothed margin and are heart-shaped in the lower part of the plant. The yellowish discolouration of the basal leaves in autumn is striking. Phlomoides tuberosa prefers a sunny-warm as well as preferably wind-protected place with summer-dry soils. In winter, the plant can withstand temperatures down to about -28 °C.
The peculiarities of the variety ˈAmazoneˈ are compact growth and more intense colour of flowers. It grows between 60 and 80 cm high.
Shrubby Jerusalem sage (Phlomis fruticosa)
Shrubby Jerusalem sage, as the name suggests, is a semi-shrub that reaches a height of about 80 cm. In Germany, the half-shrub is only green in extremely mild locations without much frost, even in winter – unlike in the subtropics, where the shrubby Jerusalem sage is green throughout and can grow much taller.
The foliage of this species strongly resembles the true sage (Salvia officinalis). The branches are covered with a grey pubescence. The labiate flowers are yellow, similar to Turkish sage. However, shrubby Jerusalem sage is not very prolific flowering, especially north of the Alps, which makes the foliage more prominent.
In the wild, the species likes to grow in rocky, stony places or old dry stone walls, so it is ideal for use in rock gardens. Mediterranean-style gardens also provide a favourable environment for shrubby Jerusalem sage. Sites can be moderately nutritious, moderately dry and in full sun.
In contrast to the previous species, Phlomis fruticosa already suffers first frost damage to the shoots from about -15 °C, which nevertheless usually sprout again from the base the next year. The safest locations are those that are mild in winter, favourable to warmth and protected from the wind. If this is not met, the species can be cultivated in larger pots and overwintered in a bright, frost-free place.
Planting Phlomis: location and method
As you have already seen from the species descriptions, the site requirements differ a little depending on the species of Jerusalem sage. In summary, the location should definitely be full sun to sunny, and the low nitrogen to moderately nutritious and rather calcareous soils are best well-drained. If the substrate is rather rich in nitrogen, this may negatively affect the frost hardiness of the plants. Optimally, the soil is moderately dry to fresh during the main growth phase – in summer, however, it may well dry out. If you want to promote the vitality of your Jerusalem sage, choose a location protected from the wind and warmth, where winter wetness does not occur. This could in fact cause problems for the plants. Jerusalem sage is best planted from mid-May, so that there is still enough time to grow. Heavy, compacted soils should be deeply loosened before planting and preferably mixed with a 30% sand content.
Smaller Jerusalem sage species or varieties can also be cultivated in pots but they should have a capacity of at least 10 litres. The substrate must be well permeable in this case. Jerusalem sage is planted either singly, in small groups of 1 to 3 plants, or in clusters of 3 to 10 specimens. The distance between plants should be about 50 cm. To meet the lower nutrient requirements of Jerusalem sage, some compost can be mixed into the soil at the time of planting. Our peat-free Plantura Organic All Purpose Compost is ideal for this purpose – its high humus content not only improves the fertility of the soil but also its ability to store water, which is important for phlomis.
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Is Jerusalem sage eaten by slugs? You do not have to worry about slugs getting a hold of your Jerusalem sage, as they are rather rare to find on it or usually already give it a wide berth.
Combine Jerusalem sage: Depending on the type of Jerusalem sage, there are some plants with which they are best combined.
- Turkish sage: Yarrow Achillea filipendulina ˈParkerˈ or the bright Dyer’s chamomile Anthemis tinctoria ˈSauce Hollandaiseˈ.
- Tuberous Jerusalem sage: Purple spice sage Salvia officinalis ˈPurpurascensˈ or whorled-leaf sage Salvia verticillata ˈPurple Rainˈ.
- Shrub Jerusalem sage: Woolly hedgenettle (Stachys byzantina), tree wormwood (Artemisia arborescens), and silver lavender (Lavandula x chaytorae).
Care
In suitable locations, Jerusalem sage proves to be quite robust and easy to care for after successful establishment. Below we explain how you can nevertheless optimally support your Jerusalem sage through a few care measures.
Watering, fertilising and pruning
Especially in long periods of drought in the summer, occasional watering can reduce stress on the plants. This is especially recommended in the year of planting. As far as nutrient supply is concerned, the annual compost application in spring is quite sufficient – if you start fertilising again later, you may risk frost damage to the plants. Because the seed stalks of Jerusalem sage are very stable and continue to be ornamental into the winter, it makes sense to cut off the withered stalks close to the ground only in the spring. In the case of shrubby Jerusalem sage, about half of the plant should be cut back. This serves, among other things, rejuvenation.
As you have already learned, Jerusalem sage reproduces by self-seeding or runners, depending on the species. If the plant is to be replanted in a particular location, it is best to distribute the mature seeds directly there in the open ground. Propagation by division in the spring is also possible – this should take place after 10 to 15 years at the latest anyway, in order to rejuvenate the plant. However, Jerusalem sage may be divided at the earliest after the successful establishment phase of 2 – 3 years, and only when the plant is sufficiently large and vital.
My Jerusalem sage is not flowering, what should I do?
Failure of Jerusalem sage to bloom can have several causes. In most cases, there is a need for action to bring the plant back to bloom.
- Site: As far as site selection is concerned, there are still some factors that may cause Jerusalem sage not to bloom. For example, the soil may be too rich in nitrogen, which primarily promotes leaf formation – or the soil may not be permeable enough, causing the plants to struggle with too much moisture. You should now either select a new location according to our recommendations or adjust the current location accordingly.
- Establishment phase: In the development of Jerusalem sage, especially after planting, it should be noted that depending on the species, it takes about 2 growing seasons until the plants are fully established. In some cases, this can also be noticeable during flowering. Therefore, if the site conditions are suitable, after planting first wait for 2-3 years.
Is Jerusalem sage hardy?
Winter hardiness of Jerusalem sage may vary somewhat depending on the species. As already mentioned, the Turkish sage with a winter hardiness of about -34 °C and the tuberous Jerusalem sage with a winter hardiness of around -28 °C are well-prepared for the cold season. They do not require additional protection. Shrubby Jerusalem sage, on the other hand, can only tolerate temperatures as low as -15 °C and is thus endangered in harsher locations. So, when choosing a species, you should take into account the location or choose a different form of culture, i.e. a planter. Finally, this can be easily wintered in a bright, frost-free place.
Toxicity and medicinal characteristics of Jerusalem sage
Jerusalem sage has no toxic effect on humans or animals. In folk medicine, the plant was used for wounds, bronchitis and colds. Unfortunately, there are hardly any studies that scientifically prove the healing characteristics of Jerusalem sage. The tubers of Phlomis tuberosa are reported to be edible when cooked and were used as food by indigenous peoples. However, tasting on your own is rather inadvisable, as you cannot know for sure how well your stomach will tolerate this unknown food.
