Rockrose

Rockrose: how do you recognise it?

Habit

A dense, rounded to cushion-shaped shrub about 1 m high and 1.5 m wide.

Leaves

Oval, 2–5 cm, dark green and slightly sticky, with a wavy margin; kept on the shrub in winter.

Flowers

Saucer-shaped, about 4 cm across, with five thin, slightly crumpled petals. Each flower lasts only one day.

Colour

Pure white with a yellow centre; the buds are tinged red to pink.

Roots

Deep and sparsely branched: it dislikes being moved, so choose the right spot from the start.

Lifespan

Not very long-lived: after a number of years the shrub becomes woody and open.

Flowering: May–July · Plants: April–May · Pruning: April and August

Why grow it?

• Evergreen: a dense, green mound in the border or on a bank, even in winter.
• Flowers from May to July, with new blooms every day from attractive pink buds.
• Bees and bumblebees come for its abundant pollen.
• Very drought-tolerant: once established it needs no more watering. Ideal for a gravel garden or a sunny slope.
• Grows on poor sandy, loamy or chalky soil, where many other shrubs struggle.

Rockrose: where does it grow best?

• Full sun: the warmer and sunnier, the better it flowers. In shade it becomes floppy and hardly flowers.
• Poor, well-drained soil: sand, loam or clay, acid to chalky. On heavy clay, first work in coarse sand or gravel.
• Dry: wet feet in winter are more dangerous to it than frost.
• Sheltered from cold, drying east winds, for example in front of a south-facing wall or on a south-facing slope.
• Allow 1–1.5 m per plant; in a group on a bank, about 1 m apart.

Light

Sun

Soil type

Sand, loam or clay

Acidity

Not fussy

Moisture

Dry

Size

1 m tall, 1.5 m wide

Hardiness

Hardy (to -15 °C)

Goes well with

• Lavender: The same sun and dry soil, with purple flowers beside the white.
• Catmint: A long blue display that carries on after the rockrose.
• Feather grass: Fine, swaying stems in a gravel garden.
• Spurge: Evergreen, with yellow flower heads in spring, before the rockrose flowers.
• Common sage: Grey, aromatic leaves that stand out nicely against the dark green.

Rockrose: when and how to plant it?

Plant in April–May.

1. Plant in April or May, so it is well rooted before winter.
2. Choose a young plant in a pot: older shrubs establish poorly.
3. Dig a hole twice as wide as the root ball; on heavy soil, mix in gravel or coarse sand for good drainage.
4. Set the plant at the same depth as it was in the pot, no deeper, and firm the soil.
5. Leave 1–1.5 m between plants and water generously straight away.
6. Mulch with gravel rather than bark: it keeps the base of the stems dry and reflects the warmth.

Care

Watering

In the first year, water during long dry spells. After that, in open ground, it needs no more watering.

Feeding

Do not feed: on rich soil it grows floppy, flowers less and is less hardy.

Mulching

A layer of gravel or grit around the base keeps weeds down and the stem base dry.

Spent flowers

No need to remove them: the petals drop by themselves at the end of the day.

In a pot

It can be grown in a large pot with a mix of potting compost and grit. Water now and then in summer and never stand the pot in a saucer of water.

Tip: Take a few cuttings every summer and overwinter them frost-free: rockroses are not long-lived and a hard winter can kill one. That way you always have a young spare plant.

Rockrose: when to prune it?

Pruning months: April and August.

When: Prune lightly after flowering, in August. In April, only cut out frost damage.

How:

• After flowering, shorten this year’s shoots by about a third to keep the shrub compact.
• Always cut into green, leafy wood and never into old, bare branches.
• In April, cut back shoots browned by frost to just above healthy green leaves.
• An old, bare shrub cannot be rejuvenated by hard pruning: replace it with a young plant grown from a cutting instead.

Caution: Never cut into old, bare wood: it usually does not produce new shoots from there.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Softwood cuttings

In June–July take 8–10 cm cuttings from non-flowering shoots, remove the lower leaves and insert them in a mix of cutting compost and sand under plastic. They usually root within a few weeks.

Semi-ripe cuttings

In August–September take cuttings of about 10 cm and put them in a cold frame. Overwinter the young plants frost-free and plant them out the following spring.

Rockrose: how does it get through the winter?

Hardy to −15 °C: protect young plants.

• Hardy to about −15 °C: in a sheltered, sunny and dry spot it comes through most Belgian winters well.
• Cold combined with wet is its worst enemy: on wet soil it can die in only moderate frost.
• In severe frost, lay fleece over the shrub and remove it as soon as the weather turns milder.
• In a pot: stand it against a south-facing wall or in a bright, unheated room and keep the compost on the dry side.

Diseases and pests

• Root rot: Yellow leaves and a plant that suddenly wilts on wet, heavy soil. Moving it rarely succeeds; give a new plant good drainage.
• Frost damage: Brown leaves and dead shoot tips after a hard winter. Wait until April, then cut back to healthy green leaves.
• Bare and woody: After a number of years the base becomes open and bare. A light trim every year delays this; replace an old plant with a young cutting.
• Few flowers: Too much shade or too rich a soil. Plant young shrubs in full sun and do not feed.

Through the year

• January: In severe frost, lay fleece over the shrub.
• April: Planting. Cut out frost damage back to healthy green leaves.
• May: Planting. The first flowers open from pink buds.
• June: In full flower; bees on the pollen. Take softwood cuttings.
• July: Last flowers. Water young plants in long dry spells.
• August: Light trim after flowering. Take semi-ripe cuttings.
• September: Take a few more cuttings as spare plants.
• October: Overwinter cuttings frost-free. Move pots against a wall.
• December: Keep fleece ready for severe frost.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• Each flower lives for only one day: it opens in the morning and by evening the petals already lie on the ground. Because new buds keep following, the shrub still flowers for weeks.
• It is a natural hybrid between Cistus populifolius and the sage-leaved rockrose, Cistus salviifolius. The old name Cistus × corbariensis refers to the Corbières in southern France.
• In the Mediterranean, rockrose seeds often germinate in large numbers after a forest fire: the heat cracks their hard seed coat.