For low hedge, bet on lavender cotton
There is an extremely drought-tolerant ground cover, cold-hardy down to zero degrees, that is known as lavender cotton (Santolina chamaecyparissus). It is seldom seen but is a pleasant garden curiosity. It is distinguished by gray foliage with a cottony consistency and scads of small yellow, spherical flowers that will remind you of those on acacia trees. This plant has a misleading name since it has no botanical relationship to lavender or cotton but is a member of the daisy family, with a close kinship to chamomile. You can also find green-leafed Santolina species. One of them, Lemon Queen, has pale yellow flower puffs. Nana is a more compact variety.
Some gardeners elect to forgo flowering of lavender cotton when used as a low-growing hedge, a garden design element for which it is better suited than any other plant. Santolina hedges can also be shaped into letters for spelling out words. A number of years ago, on a slope at the side of the road near the entrance to Jerusalem, I saw “Bruchim Habaim” (meaning “welcome”) spelled out in Hebrew letters fashioned from Santolina hedges.
Kept under a foot in height and regularly sheared and boxed, santolina foliage makes it a wonderful formal border to a bed of colorful ornamental sages (Salvia species). Sages bloom in red, pink, lavender, blue and purple, and any of these colors stand out brilliantly when surrounded by silvery santolina. Speaking of sages, “The New Book of Salvias: Sages for Every Garden” (Timber Press, 2008) is an excellent volume to give as a Valentine’s Day gift for the serious gardener in your life. It’s authored by Betsy Clebsch, and you will find detailed cultural information for growing sages, many of them appropriate for shade, and most of them with a considerable degree of drought tolerance.
Santolina, native to western and central Europe from Portugal to Yugoslavia, is derived from two Latin words: “sanctus linum,” which means “holy flax.” Its holiness comes from the supposed curative properties of its flowers and foliage. I say “supposed” because this plant has not proven to be as medicinally effective as it was thought to be at one time. When the properties of almost any plant are researched, a large number of medicinal uses are invariably listed. At one time, a physician had to be a botanist too, since medications were confined to remedies extracted from plant parts — whether leaves, flowers, bark or roots.
So why is the vaunted healing capacity of so many plants, as described in literature going back to medieval and ancient times, no longer recognized? I believe there are two reasons. First, when the only medicine available came from plants, there was more familiarity with how to utilize them — and the processes involved in extracting their beneficial ingredients — for curative purposes. Second, the conditions for growth that would result in a high concentration of the curative chemical constituents in any plant may no longer be known, conditions that are critical to growing medicinal plants for their intended effects. You would need to know how much sun or shade and what kind of soil was best for enhancing the potency of any particular species, as well as what point in their life cycle, what time of year, and what time of day were best for harvesting the relevant parts.
Over the years, most of that knowledge has been lost, although some basic rules remain. For example, the concentration of volatile oils in herbs that give them their strongest aromatic, culinary and medicinal punch occurs when flower buds have just formed but before they have opened, as all the energy of a plant is then concentrated in the leaves. These oils are also most concentrated in leaves that are picked early in the morning before the heat of the day has arrived. Incidentally, santolinas have long been used to flavor cooked dishes of every description.