categoryZUnderShrubs UnderShrubs List 
categoryZEvergreen Evergreen List 
categoryZBrooadleaf Broadleaf List 

COMMON ROCK-ROSE

Helianthemum nummularium

Rock-Rose Family [Cistaceae]

month8may month8jun month8june month8jul month8july month8aug month8sep month8sept

category
category8UnderShrubs
category
category8Evergreen
category
category8Broadleaf
status
statusZnative
flower
flower8yellow
inner
inner8orange
morph
morph8actino
petals
petalsZ5
stem
stem8round

28th May 2012, Little Orme, North Wales. Photo: © RWD
An evergreen woody undershrub that grows up to 50cm (but is often prostrate) in grassland on lime or chalky soils (only on acid soils in parts of Scotland)


28th May 2012, Little Orme, North Wales. Photo: © RWD
With yellow petals.


Photo: © RWD
On a near-vertical limestone wall. A straggly plant with broad to narrow lanceolate leaves..


28th May 2012, Little Orme, North Wales. Photo: © RWD
Five yellow petals.


28th May 2012, Little Orme, North Wales. Photo: © RWD
With a dome-shaped cluster of many yellow stamens tipped with deeper yellow anthers and pollen


28th May 2012, Little Orme, North Wales. Photo: © RWD
Pollen orange-yellow. Single central style tipped with a lime-green stigma.


28th May 2012, Little Orme, North Wales. Photo: © RWD
Fruit capsule is three valved.


10th June 2009, extinct railway, Smardale, Yorkshire Dales. Photo: © RWD
The top-most flower opens first, leaving the others drooping awaiting their turn. Sepals three wide with two reddish ridges, and two narrower and shorter with a single reddish ridge.


8th June 2007, Greenside mines, Glenridding, Cumbria. Photo: © RWD
Flower buds are hairy and have a distinctive twisted appearance.


8th June 2007, Greenside mine, Glenridding, Cumbria. Photo: © RWD
Although there are five equal petals and five sepals, the sepals are most definitely not equal; There are three equilaterally-arranged wide sepals with two reddish ridges, interspersed by two narrower ones (here partly hidden underneath two of the three wide ones).


28th May 2012, Little Orme, North Wales. Photo: © RWD
Leaves downy white underneath, and may, or may not, be sparsely hairy above. Each opposite pair of leaves has four shorter and much narrower bracts pointing upwards (which Hoary Rock-rose totally lacks). The leaves have very short stems, shorter evem than the bracts.


28th May 2012, Little Orme, North Wales. Photo: © RWD
Leaves narrow lanceolate (to broad lanceolate) and said to be hairless above, but actually may have have several glandular hairs.


28th May 2012, Little Orme, North Wales. Photo: © RWD
Leaves have a single central vein. The four smaller bracts with each leaf-pair are also in evidence here. Older stems tending to redden.


16th June 2010, Little Orme, North Wales. Photo: © RWD
There was one colony where most of the flowers had but four rather than five petals.


10th June 2009, extinct railway, Smardale, Yorkshire Dales. Photo: © RWD
With Common Rock-rose being a common or garden cultivated plant, it might be expected that there may be cultivated varieties. This, one of many similar flowers found by the garden back gate with distinct orange chevrons on the non-overlapping petals looking more like yellow Greater Periwinkles, may be one such. On the other hand, wild specimens sometimes have similar orange marks.


Not to be semantically confused with : Rock-cresses, Rock Cranesbill, Rock Cotoneaster, Hairy Rockcress, Rock Sea-Lavender, Rock Sea-Spurrey, Rock Samphire, Rock Speedwell, Rock Stonecrop or the tree Rock Whitebeam [plants with similar names]

Easily mis-identified as : Hoary Rock-rose (Helianthemum oelandicum), but see below.

Hybridizes with : White Rock-Rose (Helianthemum apenninum) (which has white flowers is itself rare) to produce Helianthemum × sulphureum which occurs in just one hectad and is very rare. Some garden Rock-roses are cultivated varieties of this hybrid.

No relation to : Rose [a plant with similar name belonging to the Rose Family (Rosaceae) to which the Rock-roses do not belong, they just have a similar number of petals as many (but not all) flowers in the Rose Family, such as Spring Cinquefoil.

Despite the 'hoary' in names of one of them,, the only two reliable differences between Hoary Rock-rose and Common Rock-rose seems to be that: [a] Common Rock-rose has short and thin stipules at the base of the stem-leaves, whereas Hoary Rock-rose does not, and [b] the style of Hairy Rock-rose is strongly S-shaped whereas it is straight in Common Rock-rose. How much hair, what type and where seems to matter a lot less, if at all. Common Rock-rose is also an evergreen whereas Hoary Rock-rose is a perennial and flowers for a much shorter period, May to June as opposed to May to Sept for Common Rock-rose.


  Helianthemum nummularium  ⇐ Global Aspect ⇒ Cistaceae  

Distribution
 family8Rock-Rose family8Cistaceae

 BSBI maps
genus8Helianthemum
Helianthemum
(Rock-Roses)

COMMON ROCK-ROSE

Helianthemum nummularium

Rock-Rose Family [Cistaceae]