🌼 Marsh Marigold – Caltha palustris
Family: Ranunculaceae
Common Names: Marsh marigold, Kingcup, Cowflock, May blob
Botanical Synonyms: Caltha palustris var. radicans, Caltha palustris var. palustris
🔬 Botanical Description
Marsh marigold is a robust, herbaceous perennial native to temperate regions of Europe, Asia, and North America. It thrives in wetlands, fens, damp meadows, and shallow water margins.
- Habit: Clump-forming, with hollow, branching stems
- Height: Typically 30–60 cm
- Leaves: Glossy, kidney- or heart-shaped, with scalloped margins
- Flowers: Bright yellow, buttercup-like, 2.5–5 cm across; not true petals but petaloid sepals
- Bloom Time: March to May, often with a second flush in autumn
- Fruit: A cluster of follicles containing black seeds
🌍 Position & Growing Conditions
- Light: Full sun to part shade
- Soil: Consistently moist to wet, humus-rich, slightly acidic to neutral (pH 5.5–7)
- Moisture: Thrives in wet soil or shallow standing water up to 10 cm deep
- Location: Ideal at the edge of ponds, bog gardens, or stream margins
If your soil is too alkaline and you’re planting in the ground (not in a pond basket), you can:
- Add ericaceous compost
- Incorporate leaf mould or pine needle mulch
- Use sulphur chips or iron sulphate to gradually lower the pH
🌡️ Temperature & Hardiness
- Hardy in RHS Zones: H7 – very hardy, tolerates temperatures down to -20°C or lower
- Climate Suitability: Perfect for the UK and other temperate zones
- Frost Tolerance: Fully frost-hardy; dies back in winter and regrows in spring
🛠️ Care & Maintenance
General Care:
- Cut back old foliage in late autumn or early spring before new growth appears
- Remove spent flowers to encourage a second flush (optional)
- Divide congested clumps every 3–5 years to maintain vigour
Feeding:
- Not usually required if planted in fertile soil or aquatic planting media
- Can benefit from a spring mulch of compost or leaf mould around the crown
Pests & Diseases:
- Generally pest-free
- Slugs may nibble young shoots, but damage is rarely serious
- Avoid waterlogged, stagnant conditions to reduce risk of rot
✂️ Pruning
- When: Late autumn (after flowering) or early spring
- How: Cut back stems to ground level before new growth emerges
- Optionally deadhead in spring to prolong bloom
🌱 Propagation
Division:
- Best method for reliable results
- When: Spring or autumn
- How: Lift clumps, tease apart rooted sections with several shoots, and replant immediately
Seed:
- Sow fresh seeds in autumn or early spring
- Requires moist conditions and light for germination
- May take 1–2 years to flower from seed
💧 Planting in a Pond or Bog Garden
In a Pond:
- Plant in aquatic baskets filled with loam-based compost (e.g., John Innes No. 2)
- Top with gravel to prevent soil washing out
- Position at the pond margin (shelf) with crown just above water, up to 10 cm deep
- Weigh basket with stone if necessary to keep stable
In a Bog Garden:
- Ensure permanent moisture—ideal with a liner or where water collects naturally
- Plant directly into the soil, spaced 30–40 cm apart
- Mulch annually to maintain soil condition
🌸 Garden Uses
- Wildlife ponds (attracts pollinators and amphibians)
- Bog gardens and damp meadows
- Naturalising in shady, wet areas
- Pairs well with Iris pseudacorus, Primula japonica, and Ligularia species
⚠️ Toxicity
- All parts are mildly toxic if ingested raw; contains protoanemonin
- Sap may cause skin irritation in sensitive individuals—wear gloves when handling
