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Plant care

Sea Campion (Bladder Campion) care

Silene uniflora

Also called Sea Campion, Bladder Campion.

RHS H7USDA 4-9Pet-safeIndoor 8–20 cm tall

Watering rhythm

1-2weeks

Every 1–2 weeks; drought-tolerant once established

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Light

Direct sun (at least 4-6 hours)

Soil

Sandy, gritty, well-drained, poor to moderate fertility

Humidity

Low to moderate (30–65% RH)

Temp

-20°C to 28°C

Pet safety

Pet-safe

Mature size

8–20 cm tall

Care at a glance

Light

Sea Campion needs sun on the leaves, not just bright ambient room light. Thrives in full sun and is adapted to the high light intensity of open coastal clifftops. Partial shade is tolerated but reduces flowering and tightens the mat less effectively. Best in an open, unshaded position. A south or west-facing windowsill in the northern hemisphere is the default; anywhere else, expect the plant to stretch and pale out within a season.

Watering

Water sea campion every 1–2 weeks; drought-tolerant once established. The actual day count varies with pot size, light, and season — the finger test (or lifting the pot to feel its weight) is more reliable than a fixed calendar. Empty any drainage saucer afterwards so the pot isn't sitting in water. Moderate watering during dry spells in the growing season. Established plants are remarkably drought-tolerant thanks to fleshy, water-storing roots. Never allow waterlogging; excellent drainage is essential, especially in winter.

Soil and pot

Sea Campion grows best in sandy, gritty, well-drained, poor to moderate fertility. Naturally grows on pure shingle and thin cliff soils. Accepts neutral to alkaline pH (6.5–8.5). Does well in sandy loam amended with grit. Rich, fertile soils produce lax growth and reduce compactness. Saline tolerance is high. 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

Sea Campion sits happiest at around Low to moderate (30–65% RH) humidity and -20°C to 28°C (-4°F to 82°F). Highly adapted to coastal air including salt spray. Tolerates variable humidity without issue. Dislikes stagnant, humid conditions inland — ensure good air circulation wherever grown. 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 sea campion sparingly. Minimal feeding required. A single light application of a balanced granular fertiliser in spring is adequate. Overfeeding promotes lush, sappy growth susceptible to aphids and reduces the characteristic neat habit. 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 sea campion in the Growli community. Each is annotated with the most common cause so you know where to start.

  • Root rot in poorly drained soil — Wet, heavy soils, particularly in winter, cause root and crown rot. Always grow in well-drained or gritty soil; raised beds or slopes are ideal in heavy-soil gardens.
  • Aphid infestations — The inflated calyces and new shoots attract aphids in spring. Treat with insecticidal soap or a gentle water jet. Avoid excess nitrogen feeding, which encourages aphid-preferred soft growth.
  • Rust disease (Puccinia) — Orange-brown pustules on leaves indicate rust fungus, which can affect Silene species. Remove affected tissue promptly, improve air circulation, and avoid wetting foliage. Copper-based fungicide can be used as a preventive.

Propagation

Divide established clumps in spring. Take semi-ripe cuttings 5–8 cm long in late spring to early summer; root in gritty compost in a cold frame. Sow seed on the surface of gritty compost in autumn for cold stratification and spring germination; seeds germinate readily without stratification when sown fresh. 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

Sea Campion is pet-safe. Silene uniflora (family Caryophyllaceae) is not individually listed by ASPCA. The genus Silene and family Caryophyllaceae have no documented toxic principles in veterinary toxicology. Historical human food use (young shoots) further supports low toxicity. 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.

Sea Campion care — frequently asked questions

What is the common name for Silene uniflora?

Silene uniflora is most commonly called Sea Campion, but it is also known as Sea Campion, Bladder Campion. The names refer to the same species, so care instructions for Sea Campion apply identically to anything sold as Bladder Campion.

How much light does sea campion need?

Sea Campion grows best in direct sun (at least 4-6 hours). Thrives in full sun and is adapted to the high light intensity of open coastal clifftops. Partial shade is tolerated but reduces flowering and tightens the mat less effectively. Best in an open, unshaded position.

How often should I water sea campion?

Water sea campion every 1–2 weeks; drought-tolerant once established. Moderate watering during dry spells in the growing season. Established plants are remarkably drought-tolerant thanks to fleshy, water-storing roots. Never allow waterlogging; excellent drainage is essential, especially 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 sea campion toxic to cats and dogs?

Sea Campion is pet-safe. Silene uniflora (family Caryophyllaceae) is not individually listed by ASPCA. The genus Silene and family Caryophyllaceae have no documented toxic principles in veterinary toxicology. Historical human food use (young shoots) further supports low toxicity.

What USDA hardiness zone does sea campion grow in?

Sea Campion is rated for USDA zone 4-9 and RHS hardiness H7. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Sea Campion deep-dive guides

Every aspect of sea campion care, each with its own calibrated guide:

Featured in these plant shortlists

Sea Campion qualifies for 9 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

Related guides

Sea Campion is also commonly called Sea Campion or Bladder Campion.