Description of Caltha polypetala (Giant Marsh Marigold)

Caltha polypetala is giant marsh marigold, also called giant kingcup. It’s a bigger, bolder version of marsh marigold, with larger yellow flowers in spring. It suits bog gardens where you want early colour and a strong clump.

Appearance

It forms rounded green leaves and produces large, buttercup-like yellow flowers in spring. It can reach 40 to 60cm tall, sometimes more in rich wet soil, and it often forms a wide clump over time.

Care Guide

It likes wet soil and cool roots. In dry springs it can flower poorly, so moisture is key.

• Sun: Sun to part shade.
• Soil: Rich, wet soil with plenty of organic matter.
• Water: Keep consistently wet, especially in spring.
• After flowering: Remove spent stems and old leaves for a tidy clump.
• Division: Divide in spring or autumn if the clump becomes too large.

In liner bogs, plant it slightly lower so the crown stays damp through spring. That’s when it needs water most.

Suitability for Bog Garden

This is excellent for bog gardens as an early-season feature plant. Place it where you will see it in spring, then let later plants grow up around it as the year goes on.

It also works at pond margins in baskets, as long as the crown is not submerged too deeply.

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