Marsh marigold (Caltha palustris) is a spring standout for water gardens, rain gardens, and any spot that stays consistently wet. You get rounded, glossy green leaves and cheerful, buttercup-like yellow flowers that open early, often when the rest of the garden is just waking up. In the right place it forms a tidy clump about 12-18 inches tall and gradually expands by rhizomes and seed.
Give it constant moisture for best results. Plant it at the edge of a pond, along a stream, in a bog garden, or in a reliably wet swale where the soil never dries out. It tolerates wet and even standing water conditions, but it resents drying out. Choose full sun for the strongest flowering, or provide partial shade (especially afternoon shade) in warmer weather to help the foliage stay attractive longer into summer.
Care is simple: keep the root zone wet, top-dress with compost if your soil is thin, and divide clumps in fall or very early spring to rejuvenate and share. After flowering, growth can slow and the plant may go dormant in heat, so pair it with later-emerging companions that can fill in around it as the season progresses.
Marsh marigold is generally low maintenance and typically deer resistant. As with many buttercup relatives, it is considered poisonous if eaten raw; enjoy it as an ornamental and keep it out of reach of pets and small children.