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Plant care

Rock Cress (Aubrieta) care

Aubrieta deltoidea

Also called Rock Cress, Aubrieta, Purple Rock Cress.

RHS H7USDA 4–8Pet-safeIndoor 10–15 cm tall

Watering rhythm

10-14days

Low; water only when soil has dried out, roughly every 10–14 days in summer

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Light

Direct sun (at least 4-6 hours)

Soil

Lean, alkaline to neutral, sharply drained soil or wall crevice

Humidity

40–60%

Temp

-20 to 25°C

Pet safety

Pet-safe

Mature size

10–15 cm tall

Care at a glance

Light

Aim for at least 4-6 hours of direct sun on the leaves. Full sun is required for the most prolific flowering and compact growth. Tolerates light partial shade but flowering is noticeably reduced. Ideal for south- or west-facing walls and rock faces. Minimum 5–6 hours of direct sun daily. If your only bright window faces south, that's perfect for rock cress — same window any aroid would fry on.

Watering

Watering rock cress: low; water only when soil has dried out, roughly every 10–14 days in summer. The number that matters isn't the day of the week — it's how dry the top 2-3 cm of the pot feels. A finger in the soil tells you more than a watering app. After every watering, tip the saucer. Drought-tolerant once established. Susceptible to root rot in waterlogged soils. Water at the base to keep foliage dry. Little supplemental watering needed in the UK climate once established in a well-drained position. Reduce further in winter.

Soil and pot

Rock Cress grows best in lean, alkaline to neutral, sharply drained soil or wall crevice. pH 6.5–8.0. Thrives in poor, stony or chalky soils. Add coarse grit to heavier garden soils to improve drainage. Actively prefers alkaline conditions — add limestone grit if soil is acidic. Rich, fertile soils produce excessive leafy growth at the expense of flowers. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Rock Cress sits happiest at around 40–60% humidity and -20 to 25°C (-4 to 77°F). Tolerates a wide range of humidity typical of temperate gardens. Good airflow is important to prevent fungal issues after the spring flowering. Dislikes humid, airless positions. If you keep the room above year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed rock cress sparingly. A light dressing of balanced, slow-release fertiliser in early spring is optional and sufficient. Avoid high-nitrogen feeds which produce excessive leafy growth. Lean soils naturally keep plants compact and floriferous. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on rock cress in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Straggly, open growth after flowering — Plants become untidy and bare at the centre if not cut back after flowering. Trim back hard by about two-thirds immediately after flowering in late spring to encourage compact, fresh growth and a second flush of blooms.
  • Powdery mildew — In dry summers or cramped, poorly ventilated positions, powdery mildew can coat leaves. Improve air circulation, water at the base, and apply a sulphur-based fungicide if severe. Hard pruning after flowering often resolves the problem.
  • Short-lived in rich, moist soils — Aubrieta thrives on neglect in lean conditions but declines in fertile, moisture-retentive soils. Improve drainage with grit and avoid feeding heavily. Plants typically live 3–5 years and should be regularly renewed from cuttings.

Propagation

Take softwood cuttings 5–8 cm long in late spring or early summer after flowering; root in gritty compost under a cold frame. Sow seed in spring at 15–18°C — named varieties must be propagated vegetatively as seed-raised plants vary. Divide established mats in early autumn. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Rock Cress is pet-safe. Aubrieta is not listed as toxic by the ASPCA. It has no known toxic principles reported in veterinary or medical literature and is widely considered safe for pets and humans in garden settings. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Rock Cress care — frequently asked questions

What is the common name for Aubrieta deltoidea?

Aubrieta deltoidea is most commonly called Rock Cress, but it is also known as Rock Cress, Aubrieta, Purple Rock Cress. The names refer to the same species, so care instructions for Rock Cress apply identically to anything sold as Aubrieta.

How much light does rock cress need?

Rock Cress grows best in direct sun (at least 4-6 hours). Full sun is required for the most prolific flowering and compact growth. Tolerates light partial shade but flowering is noticeably reduced. Ideal for south- or west-facing walls and rock faces. Minimum 5–6 hours of direct sun daily.

How often should I water rock cress?

Water rock cress low; water only when soil has dried out, roughly every 10–14 days in summer. Drought-tolerant once established. Susceptible to root rot in waterlogged soils. Water at the base to keep foliage dry. Little supplemental watering needed in the UK climate once established in a well-drained position. Reduce further in winter. The finger-test (or lifting the pot to feel its weight) beats a fixed weekly calendar because pot size, light, and season all change how fast the soil dries.

Is rock cress toxic to cats and dogs?

Rock Cress is pet-safe. Aubrieta is not listed as toxic by the ASPCA. It has no known toxic principles reported in veterinary or medical literature and is widely considered safe for pets and humans in garden settings.

What USDA hardiness zone does rock cress grow in?

Rock Cress is rated for USDA zone 4–8 and RHS hardiness H7. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Rock Cress deep-dive guides

Every aspect of rock cress care, each with its own calibrated guide:

Featured in these plant shortlists

Rock Cress qualifies for 11 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

Related guides

Rock Cress is also known as Rock Cress, Aubrieta, and Purple Rock Cress.