You can look for them under the genus names Cistus, Halimium, or X Halimiocistus--the latter including crosses of Halimium with Cistus. Despite their low water requirements, these woody and evergreen bushes don't stint on flowers. They produce spectacular magenta, pink, white, or yellow 5-petalled blooms, from 1 to 4 ½ inches across, that resemble single roses fashioned from crepe paper. Often flaunting dark "beauty spots" at the bases of their petals, those blooms unfurl in the morning and drop by mid-afternoon.
Rock rose bushes vary in height from 1 to 6 feet. Occasionally subject to sooty mold due to the high resin content in their narrow, silvery-green leaves, they seldom suffer from other pests or diseases.
That resin, also known as labdanum or ladanum has been harvested in both ancient and modern times for use in incenses and perfumes. It was most often taken from such sticky species as hoary or pink rock rose (Cistus creticus, syn. C. incanus), crimson-spot rock rose (Cistus ladanifer) pictured in the thumbnail and antique image above, and Montpelier rock rose (Cistus monspeliensis).
The ancients even extracted labdanum from the hair of goats that had browsed through the plants, by shearing the hair and boiling it, after which the fragrant oil would rise to the surface of the water and harden. If the harvesters didn't have goats on hand, they sometimes employed "rakes" with soft tines that were actually leather straps. When drawn over and through the rock rose bushes during the heat of the day those thongs soaked up the plants' precious oil, which is most liquid at temperatures in the mid-80s Fahrenheit or higher.
The hardiness of rock roses varies, according to species, from USDA zone 7 to 10. If you want to try them in zone 7, choose cultivars of one of the toughest types, such as the Cistus laurifolius pictured to the left here.
Rock rose bushes generally bloom at some point between late spring and midsummer, though some types can flower off and on for much of the year in congenial climates. In a landscape trial conducted in Oregon, the longest-blooming bush proved to be the yellow-flowered Halimium x pauanum which persevered for close to 80 days. For the largest flowers, select Cistus ladanifer 'Blanche', whose pristine white "roses" can reportedly reach up to 4 ½ inches in diameter.
I tried starting the crimson-spot rock rose from seed once. Although my seedling never got large enough to bloom, it grew amiably enough under my grow lights for at least a couple years--until I decided that it needed transferred to a larger pot. Its prompt demise proved to me these plants don't like having their roots disturbed.
When setting out a rock rose, therefore, ease it into the ground as gently as possible to avoid damaging its roots. Choose a location in full sun and plant the shrub high, with the root ball protruding slightly from the ground, to ensure excellent drainage. Then mulch it with gravel to hold the roots securely in place. Don't feed it and don't supplement its soil with organic amendments.
Once the shrub is established, you can pinch back the green tips of its stems slightly to help it bush out, but never cut them all the way back into bare wood. After that, adopt a strictly hands-off attitude. These plants can take care of themselves--and prefer to do so!
For more information on rock roses, visit the following links:
Images: The cropped and enhanced thumbnail Cistus ladanifer photo is by Juan Sanchez, courtesy of Wikimedia Commons and this license. The Cistus ladanifer antique image is from J. Moninckx's Moninckx Atlas, courtesy of plantillustrations.org. The Cistus laurifolius photo is by saya and the Halimium ocymoides and X Halimiocistus wintonensis photos are by Kelley MacDonald, all from the Dave's Garden PlantFiles.