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The Rockroses
by Randy Baldwin, San Marcos Growers
The plants commonly called Rockrose (or Rock Rose) have long been popular in California gardens. They are evergreen shrubs with flowers "born for the moment", opening early in the morning and dropping their crape-paper like petals by mid afternoon to decorate the surrounding ground through much of mid spring into summer. The name Rockrose actually refers to plants in two genera, Cistus and Halimium that with the Sunroses (Helianthemum sp.) comprise the majority of cultivated plants in the family Cistaceae. This family, with between 170-200 species in eight genera, are primarily distributed in the temperate areas of Europe and the Mediterranean Sea basin but have some new world representation in both North and South American as well. Most are subshrubs or shrubs that come from dry sunny habitats, often on poor soils.
While Halimium species are sometimes grown as an ornamental plants in California (we grow the beautiful Halimium atriplicifolium), the majority of the Rockroses cultivated in California gardens are in the genus Cistus. There are also intergeneric hybrids between these two called x Halimiocistus. Both genera are distributed naturally throughout the Mediterranean region, from Morocco and Portugal through to the Middle East, and also on the Canary Islands and Madeira. In their natural habitat these Rockroses are an important component of the vegetation types called the maquis, the European equivalent to California's chaparral and the garrigue, the soft-leaved scrubland found on limestone soils.
For the garden the Rockroses are noted for their beauty, profusion of bloom and ability to grow well on poor soils with little to no irrigation in mediterranean climates. They are evergreen low growing to large shrubs with showy yellow, pink or white flowers that open in the morning, fall off the plant by mid afternoon, and are replenished with fresh new flowers the next day. These flowers are sometimes solitary or in small clusters, usually with 5 petals crinkled like crape paper with many bright yellow stamens and primarily are spring bloomers, though along the coast this flowering can extend well into the summer with some varieties seemingly blooming years round. Flowering is much more seasonally mid spring in inland gardens.
Rockroses generally perform best in full sun to part afternoon shade and, once established, can tolerate very dry conditions, requiring little or no irrigation to look attractive in the garden. Plants irrigated infrequently to not at all in summer months are also likely to live far longer than the eight to ten years often cited as the typical lifespan in cultivation. One requirement is that the soils drain freely, which can be a problem in winter rainfall in areas with clay soil, so mounding or planting on a slope is best in heavy soils. Though Cistus species are generally considered shorter-lived shrubs they will sometimes perpetuate themselves by layering and some species self seed and one species, Cistus creticus, has even become naturalized in Santa Barbara's backcountry. Most grow fairly tall or wide and so should be planted with ample space. As a group they resent hard pruning and while they can be trimmed back lightly and even gently formally shaped in late fall or winter, this action is often at the expense of flowering.
Cistus in the Garden
The increase in popularity of the Rockroses is certainly understandable by virtue of their beauty and durability in the garden setting but there are other utilitarian reasons to plant these plants as well. Water conservation has increasingly become a valid reason to plant Rockrose, as they are quite appropriate to the low water use gardens. These gardens with mixed plantings of plants adapted to mediterranean climates have been popularized using many names such as "Drought Tolerant Gardens", "Xeriscaping (but not "Zeroscaping") and most recently as "Sustainable Landscapes", but they all essentially address the same issue of living within our resources by using plants that need little to no supplemental irrigation. For this reason alone, the Rockrose belong in our gardens. In addition, many of the Rockrose species and cultivars have became associated, rightfully or wrongly, with fire resistance and the planting of them in fire prone areas has been promoted by many municipalities. This factor is discussed in detail in our
Gardening and Wildfire section in an article titled Rockrose in the "Fire Safe" Landscape but we note here that care should always be exercised when suggesting plants for this type of use and it should be realized that ALL plants will burn when they get hot and dry enough to do so.
Rockroses come to America
Harry Morton Butterfield (1887-1970), Agriculturist Emeritus with the University of California Extension Service and Garden Editor of the Oakland Tribune, researched the introduction of plants into California and published his findings in a little known treatise titled Dates of Introduction of Trees and Shrubs to California. In this work he notes that Stephen Nolan of Bellevue Nursery in Oakland, California introduced Cistus ladaniferus [C. ladanifer], C. albidus, and C. salviifolius to western horticulture in 1871. When pioneer plantsman Dr. Francesco Franceschi arrived in Santa Barbara in 1895 he described all of the plants that he found and this list included Cistus ladaniferus [C. ladanifer].
At the time of the writing of the 1902 Libery Hyde Baily's Standard Cyclopedia of Horticulture the listing for Cistus noted them as "important garden plants" in the Old World but "little known in America" but when Baily's Hortus was published in 1935 there are 7 taxon listed with the general description changed to "The species are useful in California and stand in the southern states. They are plants long know to horticulture" and this same statement is made for the listing of Cistus for Hortus Second in 1947 with 15 taxon listed. By the time of Hortus Third, published in 1976 there were 23 taxon listed for Cistus and the comment is "The species are useful in Calif. and are grown in southern states."
This popularity was also shown in increased listings over the years in Sunset Western Garden Book where 4 species were listed in the 1947 publication and 7 by the 1954 edition. By the 1970's the full range of the genus was appreciated as evidenced by Lester Hawkins wonderful article titled "Brooms and Rock Roses; A Gardeners Guide" in the Fall 1978 issue of Pacific Horticulture Today most nurseries grow at least a few Rockroses and some list an extensive range of species and cultivars.
What's in a Name
The name Cistus was ascribed to this genus by Linnaeus from the Greek word "kistos", the name originally used to describe the plant in ancient Greece. The common name Rockrose (or Rock Rose) comes from the showy 5 petaled blooms that resemble those of wild roses. Other common names such as Gum Cistus, Resinous Rockrose and Ladanum are usually applied to Cistus ladanifer and allude to the sticky resin which is contained in the leaves and from which Ladanum has been collected since antiquity. The Spanish Name for these plant is Jaral
We are currently growing the following Rockroses at San Marcos Growers:
Cistus x hybridus
Cistus x hybridus Second Honeymoon ['Rencis'] PP 20,410
Cistus ladanifer 'Blanche'
Cistus ladanifer
Cistus x pulverulentus 'Sunset
Cistus x purpureus
Cistus salviifolius 'Prostratus'
Cistus x skanbergii
Halimium atriplicifolium
Other references on Rockrose:
Brooms and Rock Roses; A Gardeners Guide - Lester Hawkins article about Rockrose in Pacific Horticulture
Growth, Flowering, & Cold Hardiness of Rockrose in Oregon - Study by Neil Bell & James Altland on Cistus species & cultivars.
The Cistus & Halimium Website - Robert Page's website about the National Collection of Rockrose (Britain).
Cistus at Pepiniere Filippi - The Cistus of Olivier Filippi in the South of France
Digging Dog Nursery - This nursery lists more varieties of Rockrose than any other in California
Suncrest Nursery Cistus Listing - Suncrest has a good line up of Rockroses.
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