Perennial Notes Excerpts
Jerusalem sage is a plant in the throes of an identity crisis. Is it a perennial or a shrub? Should it be grown for its flower or its foliage? And why is it called a sage when it isn't in the genus Salvia? These are not concerns to lose sleep over; but, having developed a fondness for Phlomis fruticosa, I wonder why I don't see it in more Atlanta gardens.
Phlomis is derived from 'phlomos', which is Greek for mullein. The woolly, gray-green leaves of the mulleins are similar in both texture and color to those of plants in the genus Phlomis. Grouped in the Labiatae or mint family, Phlomis includes nearly one hundred species of perennials, sub-shrubs, and evergreens.
Jerusalem sage is upright and multi-stemmed, and a mature specimen can easily achieve four feet in height. Its ovate-lanceolate leaves range from one to four inches in length and are dull green above and densely hairy beneath. The prominent stems are also cloaked in white hairs. When not in bloom, Jerusalem sage looks to me like Stachys, or lamb's ears, on a stick. Tony Avent of Plant Delights Nursery notes that the whole plant is "ever gray" in winter.
When the bright yellow blooms of Jerusalem sage open in early summer, the effect is not unlike that of alighted candelabra. The hooded flowers are produced in the leaf axils. And, even though the inflorescence appears whorled, it is technically a verticillaster or false whorl that is created by the nearly sessile, opposite blooms.
While Phlomis fruticosa is usually listed with perennial plants, it is technically a sub-shrub. Over time, it becomes woody at its base, but stays soft and herbaceous near the tips. And, like some shrubs, the flowers are produced on the stems that were grown during the previous growing season.
British plantsman Christopher Lloyd considers Jerusalem sage "most beautiful when the young shoots are expanding and before it blooms." Additionally, he recommends cutting the plant back after flowering by "removing the terminal leafy shoot among a group of flowered spikes, as well as the spikes themselves." This will prevent the plant from developing a hollow center as it ages.
As one would expect from its Mediterranean origin, Jerusalem sage has an absolute requirement for full sun and excellent drainage. Incorporating granite grit or Permatil into our clay soil will prevent water from pooling around the root zone. Once its cultural needs are met, the plant is untroubled by pests or diseases. Propagate Jerusalem sage by division in the spring or fall, or by taking tip cuttings in the fall.
I find that the architectural effect of this robust species is softened by its downy foliage. It is luscious in arrangements. Its silvery foliage is a foil for virtually any companion, except another gray-leaved plant. Since I tend to favor contrast, I can envision a group of three with a purple smokebush (Cotinus coggygria 'Royal Purple') or a burgundy-leaved canna. The effect is softer with pinks, blues, and lavenders. With its foliage a presence in all seasons, it could partner a series of seasonal bloomers planted to one side or the other. Jerusalem sage is a good choice near a sunny patio or a pool, where the reflected summer heat would be too stressful for many plants.
Instead of being confused about how to categorize Phlomis fruticosa, rejoice in its versatility. I agree with Tony Avent who says, "This is one of the plants in my garden I wouldn't be without."