Crocanthemum scoparium

yellow flower fully bloomed in a plant
Santa Florencia overlook | January 2011

Rock-rose (or rush-rose; Helianthemum scoparium) is a small, early-blooming perennial found in open areas in the chaparral. In The Reserve, it seems to prefer the tops of sandstone bluffs.

The small, thirsty leaves are shed at the onset of the dry season, and the stems, which also contain chlorophyll, become the primary photosynthetic structure. The bare green twigs give the plant a unique tufted appearance that gives rise to the Latin  species name, scoparium, meaning broom.

Rock-rose is a “fire-follower”, one of many plants of the sage scrub and chaparral that have seeds that can remain dormant for many years and are stimulated to sprout by a wildfire. Thus “fire-followers” are extremely abundant for a few years following a fire, decreasing in abundance thereafter until another fire starts the cycle anew.

Other Common Names:

rush-rose, peak rush-rose, broom rose, Bisbee Peak rushrose, sunrose, common sunrose

Description 2,3,4,59

Rock-rose is a small subshrub, usually less than 1.5 feet (0.5 m) high. Many slender green (photosynthetic) stems arise from the base, extending upward and outward. Leaves are linear, usually less than one inch (2.5 cm) in length, with smooth margins. Leaves are sparse and fall after the main growth period, leaving a spray of bare stems that contain chlorophyll and continue to photosynthesize through the dry summer months. At this stage, a plant with its tuft of bare green stems resembles a small deerweed (Acmispon glaber) or spiny rush (Juncus acutus).

The yellow flowers occur in loose clusters of few to many. They are shallow-dish-shaped, radially symmetrical and bisexual, less than one inch (2.5 cm) in diameter. There are five sepals; three inner sepals are broad and triangular but the outer two are much smaller, linear in shape and inconspicuous, so the calyx appears to have only three sepals, which are green tinged with red.  The petals are obovate to fan-shaped. There are 10 or more greenish-yellow stamens in multiples of five, Stamens are of different lengths and somewhat flaccid in appearance, each with a rounded yellow anther. The pistil is yellow with an ovoid, superior ovary; unlike some,4 ours appears unlobed. A short, stout style is topped with a pale stigma with tiny hairy or finger-like projections making it resemble a pom-pom. Flowers often appear after the winter rains begin, but the main bloom time is Mar-July.1

The larger inner sepals persist and enclose the dry, ovoid seedpod which splits open when mature, releasing several small, hard, dark seeds that have rounded or angled sides. Seed coats are very hard and water-impervious.

yellow flower with 5 petals fully bloomed

Santa Florencia overlook | January 2011

dried out small seed pods at end of stem

Seedpods | Santa Florencia overlook | December 2015

bush with yellow flowers n top

Santa Florencia overlook | January 2011

Distribution 7,59

Rock-rose is native to central and southern California and northern Baja California, below 4000 feet (1300 meters). It is most common on dry, sunny23 sandstone4 slopes and bluffs in coastal sage scrub and chaparral.

In the Reserve, rock-rose is accessible from the Solana Hills trail and on the Santa Florencia overlook. In both cases, it grows on exposed sandstone in gaps in the chaparral.

Classification 2,11,59

Rock-rose is a dicot angiosperm in the rock-rose family, Cistaceae. Plants in this family have five-parted flowers and stamens in multiples of five. The overlapping sepals are of unequal sizes and the superior ovary has a short style. Seeds have a hard, impervious coat and may remain dormant for many years.41

Cistaceae is a small family and contains some useful, drought-tolerant garden plants, such as the ornamental rock-rose (Cistus spp). Rock-rose is the only representative of this family native to the Reserve, although the non-native garden rock-rose occasionally occurs.48

Alternate Scientific Names:

Helianthemum scoparium

Jepson eFlora Taxon Page
yellow flower fully open

Santa Florencia overlook | December 2015

underside of yellow rose

Santa Florencia overlook | December 2015

yellow flower opening

Santa Florencia overlook | December 2015

Ecology 14,226

Like many annuals and some subshrubs of the chaparral and sage scrub, rock-rose is a “fire-follower”, a plant that becomes extremely abundant after a wildfire, persisting for a few years before disappearing again226 – “a ‘Big Bang’ kind of reproductive strategy.”227 In a study after the 1995 Vision Fire in Point Reyes National Seashore “the most spectacular examples of short-lived, fire-adapted plants … were several legumes, … mixed with broom-rose Helianthemum scoparium, Cistaceae.”227

Most “fire followers”, including rock-rose (broom-rose), produce seeds that have a very hard, water-impermeable seed coat. Without the uptake of water, germination cannot occur, and seeds are slowly buried in the soil where they accumulate in large numbers. A wildfire breaks down the seed coat and thousands of seeds may germinate during subsequent rains. Different species respond to different stimuli under different circumstances.228 In the case of rock-rose, about 25% of the seeds germinate without fire, but germination is doubled by the heat of a fire.228 Before the Point Reyes fire, rock-rose had been listed as of doubtful occurrence in the area. After the burn, thousands of rock-roses formed “extensive turf-like patches” and persisted for at least five years before becoming rare again.227 

5 petal yellow flower

Solana Hills | Jan. 2011

bush with yellow flowers throughout

Solana Hills | Jan. 2011

microscopic view of 4 small black seeds

Seeds | Santa Florencia overlook | December 2015

Human Uses 16

The Kumeyaay boiled the flowers for a tea that helped mothers during a difficult birth.

open yellow flower in the sunlight

Santa Florencia overlook | December 2015

yellow flower open on a stem

Santa Florencia overlook | January 2011

green branches with tiny green leaves

Santa Florencia overlook | December 2015

Interesting Facts 21

“Helios” is the Greek word for sun. “Anthemon” is the Greek word for flower. Thus Helianthemum refes to the fact that rock rose opens in the sun.

yellow flower fully bloomed

Santa Florencia overlook | December 2015

5 petal yellow flower

Santa Florencia overlook | December 2015

small plants with yellow flowers inside it

Santa Florencia overlook | January 2011

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