Gum rockrose

Gum rockrose: how do you recognise it?

Habit

Upright, rather open shrub, 1–1.5 m high and 1–1.2 m wide.

Leaves

Narrow and lance-shaped, 4–10 cm, dark green and glossy-sticky above, greyish below; evergreen.

Flower

Single, up to 10 cm across, with five crinkled white petals, often with a dark blotch at the base; in June–July.

Scent

Leaves and young shoots give off a warm, balsamic scent, especially in warm weather.

Fruit

A hard, round capsule containing many small seeds.

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

Why grow it?

• Spectacular, papery flowers in early summer, renewed every day.
• Evergreen and aromatic: on warm days you can smell the balsamic resin.
• Tolerates drought and poor soil: ideal for a gravel garden or a sunny bank.
• Bees visit the open flowers for their pollen.
• Low maintenance: no feeding, hardly any watering and almost no pruning.

Gum rockrose: where does it grow best?

• Full sun and as warm as possible: a south-facing slope or the foot of a south wall is ideal.
• Poor, very well-drained soil: sand or light loam, acid to neutral.
• Dry: wet soil in winter is its worst enemy.
• Sheltered from cold winter winds; allow 1–1.2 m of space.

Light

Sun

Soil type

Sand or loam

Acidity

Acid or neutral

Moisture

Dry

Size

1.5 m tall, 1.2 m wide

Hardiness

Half hardy (to -10 °C): protect it in harsh winters

Goes well with

• Lavender: The same dry, sunny spot and a lovely purple display in summer.
• Rosemary: Another evergreen, fragrant shrub from the Mediterranean.
• Common sage: Grey leaves and blue-purple flowers next to the white rockrose.
• Jerusalem sage: Whorls of yellow flowers and grey leaves for a Mediterranean border.
• Mexican feather grass: Fine, swaying stems in a gravel garden.

Gum rockrose: when and how to plant it?

Plant in April–May.

1. Plant in April–May so it can root well before winter; do not plant in autumn.
2. Choose a young pot-grown plant: rockroses resent being moved.
3. Dig a hole and mix heavy soil with coarse sand or gravel; plant on a slight mound if the ground can get wet.
4. Set the plant at the same depth as in the pot, no deeper, and firm the soil.
5. Keep 1–1.2 m away from other plants so it gets full sun.
6. Water when planting and during dry spells in the first weeks; mulch with gravel rather than compost.

Care

Water

After the first year only in extreme drought. Too much water makes it soft and short-lived.

Feeding

Not needed: in rich soil it grows too fast and flops open.

Mulching

Use gravel or grit: it keeps the base dry and reflects warmth.

Deadheading

The petals drop by themselves; cut off the seed capsules when you trim after flowering.

Containers

Grows well in a large pot filled with compost mixed with coarse sand; keep it dry and sheltered in winter.

Tip: After flowering, trim only the faded tips and never cut into old wood. Take a few cuttings every summer, so you always have a young replacement plant.

Gum rockrose: when to prune it?

Pruning months: July–August.

When: After flowering, from late July into August, and only lightly.

How:

• Trim the faded tips and seed capsules back to just above the foliage.
• Never cut into old, bare wood: it will not reshoot from there.
• Dead branches can be removed at any time.
• An old, bare shrub cannot be renovated: replace it with a young plant or a cutting.

Caution: Never prune hard or into bare wood: rockroses do not regrow from it and often die back.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Semi-ripe cuttings

In July–August: cuttings of 8–10 cm from non-flowering shoots in a sandy cutting mix, under plastic in a bright spot. Overwinter them frost-free.

Seed

In spring, somewhere warm. Seedlings do not always resemble the parent, as rockroses hybridise easily.

Gum rockrose: how does it get through the winter?

Hardy to −10 °C: protect in harsh winters.

• Moderately hardy, to about −10 °C: it can be killed in a severe Belgian winter.
• Dry soil helps a lot: in wet soil it is much more sensitive to frost.
• In hard frost, cover it with horticultural fleece and remove it as soon as the weather turns milder.
• Take a few cuttings in summer as a back-up and overwinter them frost-free.

Diseases and pests

• Root rot: The plant wilts and dies within a short time in wet soil. Plant on a mound with plenty of gravel.
• Frost damage: Brown leaves and dead branches after a hard winter. Wait until May, then remove only the dead wood.
• Bare, sprawling shrub: Rockroses are naturally fairly short-lived and become bare with age. Replace it in time with a cutting.
• Few flowers: Too little sun or too rich a soil. Do not feed it and keep shading neighbours away.

Through the year

• January: Dormant. Fleece over the plant in hard frost.
• March: Remove fleece when it turns milder. Top up the gravel around the base.
• April: Plant. Check for frost damage.
• May: Plant. Cut out dead wood.
• June: Flowering: new white flowers every day.
• July: Flowering. Afterwards lightly trim the faded tips. Take cuttings.
• August: Trim lightly and remove seed capsules. Take cuttings.
• October: Move cuttings to a frost-free place. Put pots somewhere dry and sheltered.
• December: Dormant. Little or no water for plants in pots.

Good for wildlife

Bees

Nectar and pollen for honeybees and wild bees.

Did you know?

• The sticky resin on the leaves is called labdanum and has been used in perfumery for centuries.
• Each flower lives for just one day: it opens in the morning and drops its petals by evening.
• In the wild it is a pioneer after forest fires: the heat helps its hard seeds to germinate.