Rock soapwort

Sun

Full sun; tolerates light shade, but flowers less freely.

Water

Water regularly while establishing, then mainly during prolonged dry spells. Avoid persistently wet soil, especially in winter.

Soil

Well-drained sandy, gritty or stony soil; tolerates poor soil and neutral to alkaline conditions. Heavy clay needs substantial drainage improvement or a raised planting position.

Height

0.5-0.75 ft (0.15-0.23 m)

Spread

1-2 ft (0.3-0.6 m)

Flowers

Late spring to early summer; masses of small, five-petalled pink flowers.

Foliage

Small, oval to lance-shaped green leaves on trailing stems; evergreen in mild climates but often semi-evergreen or dormant in cold winters.

Growth

Moderate to fast in suitable conditions.

Care needed

Low

• Pollinators
• Deer resistant
• Drought tolerant
• Cold hardy
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Easy

Toughness

Very tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   0.2 ft (0.05 m)

2. After 1 year

   0.4 ft (0.12 m)

3. After 2 years

   0.6 ft (0.19 m)

   full size

About 2 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Mildly toxic: may upset a stomach

In the garden

Spreads vigorously: plan to contain it.

Growth rate

Fast

• Water new plants when the soil begins to dry; reduce watering once they are rooted.
• Keep the crown out of hollows where winter water collects.
• Skip routine feeding in ordinary garden soil; rich feeding encourages loose growth.
• Use a thin gravel mulch rather than moisture-holding mulch around the crown.
• Remove unwanted seedlings while small.

Pruning. After the main flowering period, shear back by about one-third to keep the mat compact and reduce self-seeding. Trim out dead or winter-damaged stems in spring.

Early spring

Remove winter-damaged stems and check that drainage around the crown is clear.

Spring

Plant in a sunny, freely drained position and water until established.

Late spring

Check nearby gravel and crevices for unwanted seedlings and pull them out.

Early summer

Shear back after the main flush of flowers to tidy the mat and limit seed production.

Summer

Water established plants only during prolonged drought; take non-flowering shoot cuttings if more plants are wanted.

Autumn

Clear fallen leaves from the mat so the foliage and crown do not stay wet.

• Let it spill over low retaining walls to soften stone edges with pink flowers.
• Plant between rocks on a sunny slope, with low sedums and dwarf irises.
• Use along gravel-path edges where its loose mats can spread without covering taller plants.
• Grow at the front of a dry, sunny border with catmint and small ornamental alliums.

Garden styles it suits: Alpine rock garden, Dry gravel garden, Cottage garden, Mediterranean, Low-maintenance and Pastel border.

Plant it with: Creeping thyme, Dwarf bearded iris, Catmint, Candytuft, Low-growing sedums and Ornamental alliums.

Wildlife: The flowers provide nectar and pollen for bees and other visiting insects.

• Crown or root rot in wet soil: improve drainage, move plants to raised ground and avoid frequent watering.
• Sparse flowering in shade: move to a sunnier position.
• Loose, sprawling growth in rich soil: stop feeding and shear lightly after flowering.
• Unwanted self-seeding: trim off faded flowers before seed ripens and remove seedlings promptly.

Contains saponins, particularly in the roots. Treat all parts as potentially harmful if eaten by people, cats, dogs or horses; ingestion may cause vomiting, diarrhoea or other digestive upset. Species-specific poisoning information is limited, so do not use it as food or allow animals to graze it.

• Common soapwort (Saponaria officinalis)

  Much taller and more upright, with larger leaves and pale pink or white flowers; it spreads strongly by underground runners rather than forming a low trailing mat.

• Creeping phlox (Phlox subulata)

  Has narrow, needle-like leaves and flatter flowers with distinctly notched petal tips; rock soapwort has broader leaves and flowers emerging from conspicuous tubular calyces.

• False rock cress (Aubrieta deltoidea)

  Its flowers have four petals rather than five, and its small leaves often have toothed edges.

Saponaria comes from the Latin sapo, meaning soap, referring to its lather-forming saponins, while ocymoides means resembling basil.

Propagation. Sow seed in spring, divide rooted portions of the mat in spring, or take non-flowering shoot cuttings in summer. Seedlings may vary in flower colour and habit.

Accepted botanical name

Saponaria ocymoides

In the US and Canada

Introduced in the lower 48 states.

Native range

Austria, Corse, France, Germany, Italy, Sardegna, Spain, Switzerland and Yugoslavia.

Measured

Average height 10 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.