Many common herbal plants, when grown in the garden, are drought tolerant.
They are native to Mediterranean countries where summers are dry like our own. The biome or ecosystem of Mediterranean vegetation is known as maquis, and the types of plants found in it have characteristics similar to those in our own primary ecosystem, which is known as chaparral. Chapparal comes from “chaparro,” which means dwarf or scrub oak in Spanish, and shrubby scrub oaks are dominant in both maquis and chaparral, often referred to as shrub forests.
One of the characteristics shared by maquis and chaparral plants is foliar fragrance. While garden sage (Salvia officinalis), the most used culinary sage, is from the maquis, there are highly fragrant chaparral sages as well, most notably white sage (Salvia apiana) and Cleveland sage (Salvia clevelandii). Artemisia is another example. Artemisias, many of maquis origin, are noticed for their silvery snowflake foliage although tarragon (Artemisia dracunculus) has ordinary green leaves. Our most prominent local Artemisia family member is California sagebrush (Artemisia californica). It is generally short in stature but may grow up to five feet tall, while its ‘Canyon Gray’ cultivar hugs the earth and California sandhill sage (Artemisia pynocephala) is a compact subshrub whose ‘David’s Choice’ cultivar grows only a foot tall.
Artemisias are famous for the alcoholic beverages made from them: absinthe, Pernod and vermouth. Wormwood (Artemisia absinthium) is the plant from which vermouth was originally manufactured. Vermouth (verm = worm in German) was given its name on account of its power to heal an upset stomach which, two centuries ago, was typically ascribed to the presence of intestinal worms. This same artemisia makes a most attractive hedge with its intricately cut, silvery leaves.
The essential or volatile oils that give herbs their fragrance impart drought tolerance. Like radiator coolant whose viscosity keeps water from boiling over, these oils in a plant’s sap inhibit water loss. These oils also make it easier for plants to catch fire; the heat opens the hard seed coats of some of them. Seeds may also be stimulated to germinate by chemicals contained in the smoke that wafts over them when a fire occurs. Fire is an essential element of chaparral and maquis ecosystems since it not only encourages the germination of certain seeds but provides minerals in the form of ash that will speed regrowth of the native vegetation.
Rosemary is one of the most drought-tolerant herbs under the sun. After a rosemary plant has established itself in the garden, you will never need to water it more than once a month, even in the hottest weather. The word “rosemary” is derived from dew (ros) of the sea (marinus) in Latin, and alludes to its habitat, the hills of Portugal and northwest Spain that do indeed face the sea.
Rosemary is highly medicinal due to the presence of rosmarinic acid, which is an antioxidant and anti-inflammatory as well. Dozens of scientific studies have been published regarding the beneficial effects of rosemary. At Kansas State University, for example, it was concluded that rosemary extracts, when mixed with ground beef, prevented the development of “cancer-causing compounds produced when meats are grilled, broiled or fried.” Take-home lesson: Before you barbecue your burgers, make sure to add rosemary extract to your ground beef.
A study published in the International Journal of Neuroscience revealed that misting test subjects’ cubicles with rosemary oil enhanced their overall memory and alertness. Numerous studies suggest that regular consumption of rosemary may combat the onset or advance of dementia and Alzheimer’s disease, and extend life expectancy. Perhaps the best evidence of this may be found in Acciaroli, a coastal fishing village south of Naples, Italy; 15% of the population is 100 years or older and rosemary is everywhere, being used as a spice or garnish in every meal.
When it comes to shrubs, the common myrtle (Myrtus communis), also native to the Mediterranean, is about as close to perfection as it gets. It was not by chance that, for the ancients, its diamond-shaped, highly aromatic leaves represented the all-seeing eyes of wisdom. Myrtle is covered with bedazzling white flowers with golden stamens in early summer. The blue fruit that follows is edible, if astringent, and is turned into a liqueur in its native lands. Myrtle is tolerant of all soil types, never needs water once established, and will handle a freeze just fine, being an appropriate selection for Antelope Valley gardens.
No plant native to a dry climate has leaves with a more glistening and fresher countenance than the myrtle. Normally, such polished foliage is associated with tropical plants. Somehow, the myrtle always looks like it has just been watered or rained upon, even while growing in a habitat that includes the arid lands of the Middle East.
If you are patient, your myrtle, left unpruned, will eventually become a small tree. No more than 15 or 20 feet tall at maturity, a myrtle tree is just as much about curving branches and smooth, exfoliating bark as it is about lustrous leaves. There is a compact cultivar of myrtle that is sometimes used as a low hedge, but it is susceptible to chlorosis (leaf yellowing) as a result of iron deficiency when grown in our alkaline soil. Lemon myrtle (Backhousia citriodora) is an Australian relative of the common myrtle whose leaves and flowers exude an intense lemony scent. Its growth habit is similar to that of the common myrtle and it would be eminently adaptable to Southern California gardens.
Bay leaves – used for savoring roasts, fish, and sauces – come from the evergreen Mediterranean plant known as sweet bay (Laurus nobilis) whose garlands crowned the heads of both victorious athletes in ancient Greece and Roman emperors. Bay leaves used for cooking are thoroughly dehydrated and therefore smaller than those that are freshly picked.
Sweet bay is quite versatile in the garden, being used as a 30-40 foot tall specimen tree, an 8-10 foot high informal hedge, or a low 3-4 foot formal hedge. It also makes an attractive container plant, whether outside on the patio or indoors. In our interior valleys, it grows best in morning sun; leaves facing southwest – our hottest exposure – may burn. Sweet bay has rather dense foliage and may attract scales when it is not thinned out on a regular basis.
A related species to consider, although it is slower growing than sweet bay, is the California bay tree (Umbellularia californica), which handles both sun and partial sun exposures. Its leaves may also be used in cooking, although they are more pungent than conventional bay leaves.
Tip of the Week: Lavender is cold hardy and drought tolerant. The most commonly planted lavenders are native to elevations of more than 2,000 feet – in the lower French Alps – and are hardy to 15 degrees Fahrenheit. In fact, like other cold-climate plants, their flowering is enhanced by chilling temperatures. Lavender in full bloom is a more glorious spectacle in San Francisco than in Los Angeles because of the colder winters up north.
Lavender’s needs are minimal: plenty of light and fast-draining soil. In our hot interior valleys, however, lavender grows best when given some protection from the afternoon sun. In even the hottest weather, though, lavender should never need to be watered more than once or twice a month, as long as it is slowly soaked with a hose or watered by drip irrigation, but not by overhead sprinklers. If you give lavender plenty of room on all sides, it will develop into a mound several feet in diameter so that the soil at its base is completely covered. Its roots will thus be shaded and unstressed, evaporative water loss from the soil will be all but eliminated, and you may be able to dispense with watering altogether. In the manner of most herbs, lavender only requires fertilization when grown in a container.
A large collection of lavender species and varieties, numbering a total of 21 types, is available for online ordering from Mountain Valley Growers (mountainvalleygrowers.com) in Squaw Valley, near Lake Tahoe. Those with the most intense fragrance are English lavender (Lavandula angustifolia), which is actually native to France, and Lavandin (Lavandula x intermedia). Two dwarf English lavenders (‘Hidcote’ and ‘Munstead’) have silver-gray foliage and there is also yellow lavender (Lavandula viridis), whose golden blooms contrast nicely with the violet flowers of Spanish lavender (Lavandula stoechas). Fernleaf lavender (Lavandula pinnata) has lacy, finely lobed foliage. Mountain Valley Growers is an excellent source for a wide selection of various artemisias, basils, mints, oreganos, rosemarys, scented geraniums, and thymes as well.