Caltha palustris 'Flore Pleno' (Double Marsh Marigold) care

Light

Most houseplants will scorch where caltha palustris 'flore pleno' thrives. Give it the windowsill you'd otherwise leave empty because everything else burned there. Full sun to part shade. An open, sunny position gives the most generous double blooms; light afternoon shade helps in hot summers where the soil might otherwise dry. A plant moved abruptly from low light to direct sun bleaches in 48 hours — always acclimatise over a week.

Watering

Aim for keep wet at all times; saturated soil or shallow water for caltha palustris 'flore pleno', but treat that as a starting point rather than a rule. A south-facing summer windowsill will dry the pot twice as fast as a north-facing winter room. Lift the pot; if it feels noticeably lighter than it did wet, water it. A true marginal that wants permanently boggy ground or a few centimetres of standing water at the pond edge. Never let the rootzone dry out during active growth.

Soil and pot

Caltha palustris 'Flore Pleno' grows best in rich, heavy, moisture-retentive loam or clay. Prefers fertile, humus-rich, constantly damp soil and thrives in pond-edge clay. Use aquatic compost in containers and keep the medium saturated rather than free-draining. 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

Caltha palustris 'Flore Pleno' sits happiest at around 50-80% humidity and -30 to 24°C (-22 to 75°F). A waterside plant happy in high humidity, but outdoors the priority is a wet rootzone rather than air moisture. It is undemanding on ambient humidity once its feet stay wet. 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 caltha palustris 'flore pleno' sparingly. Light feeder. A spring mulch of well-rotted organic matter or a single balanced slow-release feed suffices; in rich pond mud extra feeding is rarely needed and excess only encourages leaf over flower. 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 caltha palustris 'flore pleno' in the Growli community. Each is annotated with the most common cause so you know where to start.

• Summer dieback — Normal post-flowering dormancy, especially in dry heat — foliage yellows and dies down. Keep the soil wet and growth resumes in spring.
• Reduced doubling — Flowers may revert toward single in poor light or stress. Grow in full sun and consistently wet, fertile soil to keep blooms fully double.
• Powdery mildew — White film on foliage in dry or congested settings. Improve airflow and maintain a saturated rootzone to lower stress.
• Drying out — As a bog plant it wilts quickly if the soil dries. Maintain permanently wet ground or a shallow water margin.

Propagation

Propagate only by division in early autumn or just after flowering, since the double form is sterile and sets no viable seed. Replant divisions into wet soil. 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

Caltha palustris 'Flore Pleno' is toxic to pets. Like the species, this double cultivar is in the buttercup family (Ranunculaceae) and contains protoanemonin. Caltha is not individually named on ASPCA's list, but Ranunculaceae protoanemonin causes drooling, oral and gastrointestinal irritation, vomiting and diarrhoea in dogs and cats. Treat as toxic, keep pets from chewing the plant, and contact a vet if it is ingested. 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.

Caltha palustris 'Flore Pleno' deep-dive guides

Every aspect of caltha palustris 'flore pleno' care, each with its own calibrated guide:

• Caltha palustris 'Flore Pleno' watering schedule
• Caltha palustris 'Flore Pleno' light requirements
• Best soil mix for caltha palustris 'flore pleno'
• Caltha palustris 'Flore Pleno' fertilizing guide
• When to repot caltha palustris 'flore pleno'
• How to propagate caltha palustris 'flore pleno'
• Caltha palustris 'Flore Pleno' growth rate & size
• Caltha palustris 'Flore Pleno' cold hardiness
• Caltha palustris 'Flore Pleno' temperature & humidity
• Is caltha palustris 'flore pleno' toxic to cats & dogs?
• Is caltha palustris 'flore pleno' toxic to cats?
• Is caltha palustris 'flore pleno' toxic to dogs?
• Getting caltha palustris 'flore pleno' to bloom

Featured in these plant shortlists

Caltha palustris 'Flore Pleno' qualifies for 6 curated Growli shortlists — each one filtered objectively from our structured plant-care library, so the selection is consistent and checkable:

• Best humidity-loving houseplants — Houseplants that thrive in a bathroom, kitchen, or by a humidifier — selected by documented humidity preference.
• Best flowering houseplants — Indoor plants grown for their blooms — selected from the flowering species in Growli’s plant-care library.
• Houseplants toxic to cats & dogs — The common houseplants the ASPCA lists as toxic to cats and dogs — the ones to keep out of reach, each with its symptoms and a safe alternative.
• Best small & tabletop houseplants — Compact houseplants that stay under about 40 cm — desk, shelf and windowsill plants that never outgrow a small space.
• Best houseplants for full sun — Houseplants that want direct sun — the species for a hot south or west-facing windowsill where shade-lovers scorch.
• Best houseplants for a cool room — Houseplants that tolerate cool conditions down to about 10°C — for an unheated spare room, hallway, porch or a home kept cool.
• Browse all 29 plant shortlists — pet-safe, low-light, drought-tolerant and more

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Caltha palustris 'Flore Pleno' is also commonly called Double Marsh Marigold or Double Kingcup.

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