All of the members of the Cistus genus and its hybrids are evergreen, aromatic shrubs with characteristic saucer-shaped flowers (usually with five petals and a yellow basal spot). The flowers resemble those of old-fashioned or antique roses, and the common name refers to their ability to grow in poor, rocky soil. They are native to the Mediterranean coastline and are found in both the stony scrubland and in the dry woodlands and open pine forests of higher elevations. They grow in full sun in soil that has little nutrient value or organic matter but is well-drained. They prefer lighter soil in cultivation but will tolerate heavier clay soil if it is free-draining. They also tolerate ocean winds and salt spray. Most species exhibit a long blooming period of three to four weeks, and the sterile hybrids extend that. Most have aromatic evergreen leaves ranging in color from dark-green to gray. The leaves are oppositely arranged on the branch and may be quite narrow or oval, often downy, and occasionally have wavy leaf margins. They are all sun lovers and exude their unusual resinous fragrance in the afternoon heat.
As for winter hardiness, cistus thrives in the Pacific Coast area, which closely resembles its native Mediterranean climate. They are generally more winter hardy than some references would have you believe (hardy in Zones 7 through 9, borderline in Zones 4 through 6). Most rock roses, if given wind-sheltered sites, are cold-hardy to temperatures around 10°F. Hardier species, which include C. laurifolius, C. salviifolius, and some hybrids, such as C. ¥corbariensis, C. ¥purpureus, and C. ‘Silver Pink’, may tolerate temperatures as low as 5°F. They resent heavy pruning and root disturbance. I prune the tips of young plants to promote branching, and later, when they have matured, I prune out only the dead wood. Avoid overfertilizing container-grown plants as this may promote soft growth susceptible to winter damage. The plants are remarkably maintenance-free and have no serious pest or disease problems. In fact, they provide a great home to my resident praying mantises, which blend in with the foliage and thrive despite the stickiness of the leaves. I have observed that younger plants bloom more profusely than older plants, which may live as long as ten years or more.
I do all of my propagation of rock roses from semi-hardwood tip cuttings taken in the spring or fall. I prefer cuttings to seed propagation as this ensures that I get the same plant, even with the hybrids. Although, I must warn you that taking cuttings of C. ladanifer is a very sticky business. After stripping leaves off of several cuttings, my fingertips are black and almost as sticky as super glue! Soap and water doesn’t work well in removing the sticky gum from the skin. Try baby oil.
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Andy Van Hevelingen is a frequent contributor to The Herb Companion and enjoys writing, photography, and gardening in his Newberg, Oregon, home.