Common rock-rose

Common rock-rose: how do you recognise it?

Habit

Low, sprawling shrublet 10–30 cm tall and about 0.5 m across; evergreen.

Leaf

Opposite, 1–3 cm, elliptic to lanceolate, with a rolled edge and a grey-felted underside; small stipules at the base.

Stems

Trailing, woody stems.

Flower

Bright yellow flowers (2–2.5 cm) with 5 crumpled petals and many stamens, in loose clusters, June–September. Garden forms also in white, pink, orange or red.

Fruit

Small capsules with three valves.

Difference from tormentil

Tormentil (Potentilla erecta) is a herb with 4 yellow petals and trifoliate, toothed leaves.

Flowering: June–August · Pruning: July–August

Looks like it, but isn’t

• Tormentil (Potentilla erecta): a herb with 4 yellow petals and trifoliate, toothed leaves.

Why grow it?

• A carpet of yellow flowers from June to September, often with a second flush after pruning.
• Native and a food plant of the brown argus butterfly; the flowers attract bees.
• Grows on dry, poor, chalky soil where little else will flower.
• Garden forms in many colours, for a rock garden, low wall or slope.

Common rock-rose: where does it grow best?

• Full sun: in shade it hardly flowers.
• Dry, poor, well-drained soil, preferably chalky; no wet roots.
• Ideal among stones: in a rock garden, on a low wall, a sunny slope or in a gravel garden.
• Allow about 50 cm across per plant.

Light

Full sun

Legal basis

Any garden soil

Moisture

Dry

Size

0.2 m tall, 0.5 m wide

Hardiness

Throughout Belgium, no protection needed

Goes well with

• Garden thyme: A low, fragrant cushion for the same dry, chalky soil, with pink flowers for bees.
• English lavender: Purple flower spikes above the yellow carpet, for the same sunny spot.
• Wild marjoram: A native plant of dry chalk grassland, like the rock-rose; its pink flowers attract many butterflies.

Good and bad companions

Best kept away from

• Do not plant under the dense crown of these trees: norway spruce, european silver fir, nordmann fir, douglas fir, yew, horse chestnut, norway maple, sycamore

Common rock-rose: when and how to plant it?

1. Plant in spring (April–May) or in September, from a pot.
2. Space plants 30–40 cm apart; in a group they quickly form a closed carpet.
3. On heavy soil: work in coarse sand, gravel or grit, or plant on a raised bed or low wall.
4. Don’t add compost or manure: on rich soil it grows floppy and flowers less.

Care

Watering

Only for the first few weeks after planting; after that it copes on its own, even in dry summers.

Feeding

Not needed: it likes poor soil.

Weeding

Keep grasses and weeds out of the carpet, or they will grow through it.

Renewal

After a few years a plant becomes woody and bare in the middle: replace it with a young plant or a cutting.

Tip: Plant rock-roses on a low wall or at the top of a slope: the flowering stems then spill attractively over the edge, and in winter the water drains away quickly.

Common rock-rose: when to prune it?

Pruning months: July–August.

When: After the first flush of flowers, in July–August.

How:

• Cut the flowered stems back by a third to a half: the plant stays compact and often flowers a second time.
• Trim a larger carpet with hedge shears or grass shears.
• If you want seed, leave a few stems until the capsules turn brown.

Caution: Don’t cut back into bare, old wood.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Cuttings

In summer, take cuttings of about 5 cm from non-flowering shoots and root them in a sandy mix under glass or plastic.

Sowing

Sow the wild species in spring in a sandy mix; garden forms are propagated from cuttings, as seedlings don’t resemble the parent.

Common rock-rose: how does it get through the winter?

Hardy throughout Belgium: no protection needed.

• Hardy and evergreen; wet soil in winter is more dangerous than frost.
• Don’t prune in autumn: let the plant go into winter as it is.

Diseases and pests

• Root rot: The plant discolours and dies after a wet winter. Make sure the soil is well drained, sandy or gritty.
• Powdery mildew: White coating on the leaves, especially in late summer. Cut off affected stems; a sunny, airy spot helps.
• Bare in the middle: An old plant becomes woody and bare. Prune every year after flowering, and replace a bare plant with a cutting.

Through the year

• April: Planting from pots.
• May: Planting; weed the carpet.
• June: Flowering begins: new flowers every day.
• July: Pruning after the first flush; taking cuttings.
• August: Last month for pruning; the second flush begins.
• September: Second flush; planting is still possible.

What can you use it for?

Garden and landscape

Low, flowering carpet for a rock garden, low wall or sunny, dry slope; garden forms in many colours.

For wildlife

Food plant of the brown argus butterfly; the flowers attract bees.

Did you know?

• Each flower lasts only one day. When an insect touches the stamens, they bend outwards.
• Helianthemum means ‘sun flower’ (Greek hēlios, sun, and anthemon, flower): the flowers open in the sun.
• The brown argus, a small brown butterfly with orange spots along the wing edges, lays its eggs on rock-rose, among other plants.